Implement Regular Expression replace and update Text.replace to the new API (#5959)

Re-implement replace on top of Truffle regex.

CHANGELOG.md

@@ -363,6 +363,8 @@
 - [Aligned names of columns created by column operations.][5850]
 - [Improved `cross_tab`. Renamed `fill_missing` and `is_missing` to
   `fill_nothing` and `is_nothing`. Added `fill_empty`.][5863]
+- [Removed many regex compile flags from `replace`; added `only_first`
+  flag.][5959]
 
 [debug-shortcuts]:
   https://github.com/enso-org/enso/blob/develop/app/gui/docs/product/shortcuts.md#debug
@@ -550,6 +552,7 @@
 [5863]: https://github.com/enso-org/enso/pull/5863
 [5917]: https://github.com/enso-org/enso/pull/5917
 [5705]: https://github.com/enso-org/enso/pull/5705
+[5959]: https://github.com/enso-org/enso/pull/5959
 
 #### Enso Compiler
 

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Text/Extensions.enso

@@ -10,6 +10,7 @@ import project.Data.Range.Range
 import project.Data.Text.Case.Case
 import project.Data.Text.Case_Sensitivity.Case_Sensitivity
 import project.Data.Text.Encoding.Encoding
+import project.Data.Text.Helpers
 import project.Data.Text.Location.Location
 import project.Data.Text.Matching_Mode.Matching_Mode
 import project.Data.Text.Regex.Match.Match
@@ -218,6 +219,10 @@ Text.characters self =
    - case_sensitivity: Specifies if the text values should be compared case
      sensitively.
 
+   If an empty regex is used, `find` throws an Illegal_Argument error.
+
+   If a non-default locale is used, `find` throws an Illegal_Argument error.
+
    > Example
      Find the first substring matching the regex.
 
@@ -227,10 +232,12 @@ Text.characters self =
          example_find_insensitive =
              ## This matches `aBc` @ character 11
              "aabbbbccccaaBcaaaa".find "a[ab]c" Case_Sensitivity.Insensitive
-Text.find : Text -> Case_Sensitivity -> Match | Nothing ! Regex_Syntax_Error
+Text.find : Text -> Case_Sensitivity -> Match | Nothing ! Regex_Syntax_Error | Illegal_Argument
 Text.find self pattern=".*" case_sensitivity=Case_Sensitivity.Sensitive =
+    Helpers.regex_assume_default_locale case_sensitivity <|
         case_insensitive = case_sensitivity.is_case_insensitive_in_memory
-    Regex_2.compile pattern case_insensitive=case_insensitive . match self
+        compiled_pattern = Regex_2.compile pattern case_insensitive=case_insensitive
+        compiled_pattern.if_not_error <| compiled_pattern.match self
 
 ## Finds all the matches of the regular expression `pattern` in `self`,
    returning a Vector. If not found, will be an empty Vector.
@@ -240,6 +247,10 @@ Text.find self pattern=".*" case_sensitivity=Case_Sensitivity.Sensitive =
    - case_sensitivity: Specifies if the text values should be compared case
      sensitively.
 
+   If an empty regex is used, `find_all` throws an Illegal_Argument error.
+
+   If a non-default locale is used, `find_all` throws an Illegal_Argument error.
+
    > Example
      Find the substring matching the regex.
 
@@ -249,10 +260,12 @@ Text.find self pattern=".*" case_sensitivity=Case_Sensitivity.Sensitive =
          example_find_all_insensitive =
               ## This matches `aABbbbc` @ character 0 and `aBC` @ character 11
              "aABbbbccccaaBCaaaa".find_all "a[ab]+c" Case_Sensitivity.Insensitive
-Text.find_all : Text -> Case_Sensitivity -> Vector Match ! Regex_Syntax_Error
+Text.find_all : Text -> Case_Sensitivity -> Vector Match ! Regex_Syntax_Error | Illegal_Argument
 Text.find_all self pattern=".*" case_sensitivity=Case_Sensitivity.Sensitive =
+    Helpers.regex_assume_default_locale case_sensitivity <|
         case_insensitive = case_sensitivity.is_case_insensitive_in_memory
-    Regex_2.compile pattern case_insensitive=case_insensitive . match_all self
+        compiled_pattern = Regex_2.compile pattern case_insensitive=case_insensitive
+        compiled_pattern.if_not_error <| compiled_pattern.match_all self
 
 ## ALIAS Check Matches
 
@@ -263,6 +276,10 @@ Text.find_all self pattern=".*" case_sensitivity=Case_Sensitivity.Sensitive =
    - case_sensitivity: Specifies if the text values should be compared case
      sensitively.
 
+   If an empty regex is used, `match` throws an Illegal_Argument error.
+
+   If a non-default locale is used, `match` throws an Illegal_Argument error.
+
    > Example
      Checks if whole text matches a basic email regex.
 
@@ -274,11 +291,12 @@ Text.find_all self pattern=".*" case_sensitivity=Case_Sensitivity.Sensitive =
              regex = ".+ct@.+"
              # Evaluates to true
              "CONTACT@enso.org".match regex Case_Sensitivity.Insensitive
-Text.match : Text -> Case_Sensitivity -> Boolean ! Regex_Syntax_Error
+Text.match : Text -> Case_Sensitivity -> Boolean ! Regex_Syntax_Error | Illegal_Argument
 Text.match self pattern=".*" case_sensitivity=Case_Sensitivity.Sensitive =
+    Helpers.regex_assume_default_locale case_sensitivity <|
         case_insensitive = case_sensitivity.is_case_insensitive_in_memory
         compiled_pattern = Regex_2.compile pattern case_insensitive=case_insensitive
-    compiled_pattern.matches self
+        compiled_pattern.if_not_error <| compiled_pattern.matches self
 
 ## ALIAS Split Text
 
@@ -327,21 +345,31 @@ Text.split self delimiter="," matcher=Text_Matcher.Case_Sensitive = if delimiter
             compiled_pattern.split self mode=Regex_Mode.All
 
 ## ALIAS Replace Text
-   Replaces the first, last, or all occurrences of term with new_text in the
-   input. If `term` is empty, the function returns the input unchanged.
+   Perform a text or regex replace.
+
+   Returns the text with all matched elements replaced by the provided
+   replacement. If `input` is empty, the function returns the input unchanged.
+
+   The replacement string can contain references to groups matched by the
+   regex. The following syntaxes are supported:
+       $0: the entire match string
+       $&: the entire match string
+       $n: the nth group
+       $<foo>: Named group `foo`
 
    Arguments:
-   - term: The term to find.
-   - new_text: The new text to replace occurrences of `term` with.
-     If `matcher` is a `Regex_Matcher`, `new_text` can include replacement
-     patterns (such as `$<n>`) for a marked group.
-   - mode: Specifies which occurences of term the engine tries to find. When the
-     mode is `First` or `Last`, this method replaces the first or last occurence
-     of term in the input. If set to `All`, it replaces all occurences of term in
-     the input.
-   - matcher: If a `Text_Matcher`, the text is compared using case-sensitivity
-     rules specified in the matcher. If a `Regex_Matcher`, the term is used as a
-     regular expression and matched using the associated options.
+   - term: The string or regex to find.
+   - replacement: The text to replace matches with.
+   - case_insensitive: Enables or disables case-insensitive matching. Case
+     insensitive matching behaves as if it normalises the case of all input
+     text before matching on it.
+   - only_first: If True, only replace the first match.
+   - use_regex: If true, the term is used as a regular expression.
+
+   If an empty regex is used, `replace` throws an Illegal_Argument error.
+
+   If a non-default locale is used with a regex, `replace` throws an
+   Illegal_Argument error.
 
    > Example
      Replace letters in the text "aaa".
@@ -351,17 +379,17 @@ Text.split self delimiter="," matcher=Text_Matcher.Case_Sensitive = if delimiter
    > Example
      Replace all occurrences of letters 'l' and 'o' with '#'.
 
-         "Hello World!".replace "[lo]" "#" matcher=Regex_Matcher == "He### W#r#d!"
+         "Hello World!".replace "[lo]" "#" use_regex=True == "He### W#r#d!"
 
    > Example
      Replace the first occurrence of letter 'l' with '#'.
 
-         "Hello World!".replace "l" "#" mode=Matching_Mode.First == "He#lo World!"
+         "Hello World!".replace "l" "#" only_first=True == "He#lo World!"
 
    > Example
      Replace texts in quotes with parentheses.
 
-          '"abc" foo "bar" baz'.replace '"(.*?)"' '($1)' matcher=Regex_Matcher == '(abc) foo (bar) baz'
+          '"abc" foo "bar" baz'.replace '"(.*?)"' '($1)' use_regex=True == '(abc) foo (bar) baz'
 
    ! Matching Grapheme Clusters
      In case-insensitive mode, a single character can match multiple characters,
@@ -379,61 +407,39 @@ Text.split self delimiter="," matcher=Text_Matcher.Case_Sensitive = if delimiter
      Extended partial matches in case-insensitive mode.
 
          # The ß symbol matches the letter `S` twice in case-insensitive mode, because it folds to `ss`.
-         'ß'.replace 'S' 'A' matcher=(Text_Matcher Case_Insensitive) . should_equal 'AA'
+         'ß'.replace 'S' 'A' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'AA'
          # The 'ffi' ligature is a single grapheme cluster, so even if just a part of it is matched, the whole grapheme is replaced.
-         'affib'.replace 'i' 'X' matcher=(Text_Matcher Case_Insensitive) . should_equal 'aXb'
-
-   ! Last Match in Regex Mode
-     Regex always performs the search from the front and matching the last
-     occurrence means selecting the last of the matches while still generating
-     matches from the beginning. Regex does not return overlapping matches - it
-     will return a match at some position and then continue the search after that
-     match. This will lead to slightly different behavior for overlapping
-     occurrences of a pattern in Regex mode than in exact text matching mode
-     where the matches are searched for from the back.
+         'affib'.replace 'i' 'X' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'aXb'
 
    > Example
-     Comparing Matching in Last Mode in Regex and Text mode
+     Regexp replace.
 
-         "aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Text_Matcher . should_equal "ac"
-         "aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Regex_Matcher . should_equal "ca"
+     '<a href="url">content</a>'.replace '<a href="(.*?)">(.*?)</a>' '$2 is at $1' use_regex=True == 'content is at url'
 
-         "aaa aaa".replace "aa" "c" matcher=Text_Matcher . should_equal "ca ca"
-         "aaa aaa".replace "aa" "c" mode=Matching_Mode.First matcher=Text_Matcher . should_equal "ca aaa"
-         "aaa aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Text_Matcher . should_equal "aaa ac"
-         "aaa aaa".replace "aa" "c" matcher=Regex_Matcher . should_equal "ca ca"
-         "aaa aaa".replace "aa" "c" mode=Matching_Mode.First matcher=Regex_Matcher . should_equal "ca aaa"
-         "aaa aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Regex_Matcher . should_equal "aaa ca"
-Text.replace : Text -> Text -> Matching_Mode | Regex_Mode -> (Text_Matcher | Regex_Matcher) -> Text
-Text.replace self term="" new_text="" mode=Regex_Mode.All matcher=Text_Matcher.Case_Sensitive = if term.is_empty then self else
-    case matcher of
-        _ : Text_Matcher ->
+Text.replace : Text -> Text -> Case_Sensitivity -> Boolean -> Boolean -> Text ! Illegal_Argument
+Text.replace self term replacement case_sensitivity=Case_Sensitivity.Sensitive only_first=False use_regex=False =
+    case use_regex of
+        False -> if term.is_empty then self else
             array_from_single_result result = case result of
                 Nothing -> Array.empty
                 _ -> Array.new_1 result
-            spans_array = case matcher of
-                Text_Matcher.Case_Sensitive -> case mode of
-                    Regex_Mode.All ->
-                        Text_Utils.span_of_all self term
-                    Matching_Mode.First ->
-                        array_from_single_result <| Text_Utils.span_of self term
-                    Matching_Mode.Last ->
-                        array_from_single_result <| Text_Utils.last_span_of self term
-                    _ -> Error.throw (Illegal_Argument.Error "Invalid mode.")
-                Text_Matcher.Case_Insensitive locale -> case mode of
-                    Regex_Mode.All ->
+            spans_array = case case_sensitivity of
+                Case_Sensitivity.Sensitive -> case only_first of
+                    False -> Text_Utils.span_of_all self term
+                    True -> array_from_single_result <| Text_Utils.span_of self term
+                Case_Sensitivity.Insensitive locale -> case only_first of
+                    False ->
                         Text_Utils.span_of_all_case_insensitive self term locale.java_locale
-                    Matching_Mode.First ->
+                    True ->
                         array_from_single_result <|
                             Text_Utils.span_of_case_insensitive self term locale.java_locale False
-                    Matching_Mode.Last ->
-                        array_from_single_result <|
-                            Text_Utils.span_of_case_insensitive self term locale.java_locale True
-                    _ -> Error.throw (Illegal_Argument.Error "Invalid mode.")
-            Text_Utils.replace_spans self spans_array new_text
-        _ : Regex_Matcher ->
-            compiled_pattern = matcher.compile term
-            compiled_pattern.replace self new_text mode=mode
+            Text_Utils.replace_spans self spans_array replacement
+        True ->
+            Helpers.regex_assume_default_locale case_sensitivity <|
+                case_insensitive = case_sensitivity.is_case_insensitive_in_memory
+                compiled_pattern = Regex_2.compile term case_insensitive=case_insensitive
+                compiled_pattern.if_not_error <|
+                    compiled_pattern.replace self replacement only_first
 
 ## ALIAS Get Words
 
@@ -1115,9 +1121,9 @@ Text.trim self where=Location.Both what=_.is_whitespace =
 
          term = "straße"
          text = "MONUMENTENSTRASSE 42"
-         match = text . locate term matcher=(Text_Matcher Case_Insensitive)
-         term.length == 6
-         match.length == 7
+         match = text . locate term case_sensitivity=Case_Sensitivity.Insensitive
+         term.length . should_equal 6
+         match.length . should_equal 7
 
    ! Matching Grapheme Clusters
      In case-insensitive mode, a single character can match multiple characters,
@@ -1265,11 +1271,8 @@ Text.locate_all self term="" case_sensitivity=Case_Sensitivity.Sensitive = if te
    - term: The term to find.
    - start: The index to start searching from. If the index is negative, it
      is counted from the end of the vector.
-   - matcher: Specifies how the term is matched against the input:
-     - If a `Text_Matcher`, the text is compared using case-sensitively rules
-       specified in the matcher.
-     - If a `Regex_Matcher`, the `term` is used as a regular expression and
-       matched using the associated options.
+   - case_sensitivity: Specifies if the text values should be compared case
+     sensitively.
 
    ! What is a Character?
      A character is defined as an Extended Grapheme Cluster, see Unicode
@@ -1301,11 +1304,8 @@ Text.index_of self term="" start=0 case_sensitivity=Case_Sensitivity.Sensitive =
    - term: The term to find.
    - start: The index to start searching backwards from. If the index is
      negative, it is counted from the end of the vector.
-   - matcher: Specifies how the term is matched against the input:
-     - If a `Text_Matcher`, the text is compared using case-sensitively rules
-       specified in the matcher.
-     - If a `Regex_Matcher`, the `term` is used as a regular expression and
-       matched using the associated options.
+   - case_sensitivity: Specifies if the text values should be compared case
+     sensitively.
 
    ! What is a Character?
      A character is defined as an Extended Grapheme Cluster, see Unicode

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Text/Helpers.enso

@@ -0,0 +1,16 @@
+from Standard.Base import all
+
+import project.Any.Any
+import project.Data.Locale.Locale
+import project.Data.Text.Case_Sensitivity.Case_Sensitivity
+import project.Errors.Illegal_Argument.Illegal_Argument
+
+## PRIVATE
+regex_assume_default_locale : Case_Sensitivity -> Any -> Any ! Illegal_Argument
+regex_assume_default_locale case_sensitivity ~action = case case_sensitivity of
+    Case_Sensitivity.Sensitive -> action
+    Case_Sensitivity.Insensitive locale -> case locale == Locale.default of
+        True -> action
+        False ->
+            msg = "Custom locales are not supported for regexes."
+            Error.throw (Illegal_Argument.Error msg)

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Text/Regex/Match_2.enso

@@ -8,8 +8,8 @@ import project.Data.Text.Span.Span
 import project.Data.Text.Span.Utf_16_Span
 import project.Data.Text.Text
 import project.Data.Vector.Vector
-import project.Errors.Common.Index_Out_Of_Bounds
 import project.Error.Error
+import project.Errors.Common.Index_Out_Of_Bounds
 import project.Nothing.Nothing
 import project.Panic.Panic
 
@@ -48,9 +48,9 @@ type Match_2
        Arguments:
        - group: the group name or number. Marked groups defined in the regex are
          numbered starting at 1; group 0 refers to the entire match.
-    utf16_start : Integer | Text -> Integer
-    utf16_start self group=0 =
-        span = self.span group
+    utf_16_start : Integer | Text -> Integer
+    utf_16_start self group=0 =
+        span = self.utf_16_span group
         if span.is_nothing then Nothing else span.start
 
     ## Returns the end UTF16 character index, plus one, of a group.
@@ -58,9 +58,9 @@ type Match_2
        Arguments:
        - group: the group name or number. Marked groups defined in the regex are
          numbered starting at 1; group 0 refers to the entire match.
-    utf16_end : Integer | Text -> Integer
-    utf16_end self group=0 =
-        span = self.span group
+    utf_16_end : Integer | Text -> Integer
+    utf_16_end self group=0 =
+        span = self.utf_16_span group
         if span.is_nothing then Nothing else span.end
 
     ## Returns the start grapheme index of a group.
@@ -75,7 +75,7 @@ type Match_2
          numbered starting at 1; group 0 refers to the entire match.
     start : Integer | Text -> Integer
     start self group=0 =
-        span = self.grapheme_span group
+        span = self.span group
         if span.is_nothing then Nothing else span.start
 
     ## Returns the end grapheme index, plus one, of a group.
@@ -90,7 +90,7 @@ type Match_2
          numbered starting at 1; group 0 refers to the entire match.
     end : Integer | Text -> Integer
     end self group=0 =
-        span = self.grapheme_span group
+        span = self.span group
         if span.is_nothing then Nothing else span.end
 
     ## Gets the UTF16 span matched by the group with the provided identifier, or
@@ -120,9 +120,9 @@ type Match_2
 
        In this case, the group id for "(d)", which is 3, is a valid group id and
        (Pattern_2.lookup_group 3) will return 3. If the caller tries to get group 3,
-       Match_2.group will return the default value.
-    span : Integer | Text -> Any -> Utf_16_Span ! No_Such_Group
-    span self group=0 ~default=Nothing =
+       Match_2.utf_16_span will return the default value.
+    utf_16_span : Integer | Text -> Any -> Utf_16_Span ! No_Such_Group
+    utf_16_span self group=0 ~default=Nothing =
         group_id = self.pattern.lookup_group group
         start = self.internal_start group_id
         end = self.internal_end group_id
@@ -158,10 +158,10 @@ type Match_2
 
        In this case, the group id for "(d)", which is 3, is a valid group id and
        (Pattern_2.lookup_group 3) will return 3. If the caller tries to get
-       group 3, Match_2.group will return the default value.
-    grapheme_span : Integer | Text -> Any -> Span ! No_Such_Group
-    grapheme_span self group=0 ~default=Nothing =
-        result = self.span group Nothing
+       group 3, Match_2.span will return the default value.
+    span : Integer | Text -> Any -> Span ! No_Such_Group
+    span self group=0 ~default=Nothing =
+        result = self.utf_16_span group Nothing
         if result.is_nothing then default else result.to_grapheme_span
 
     ## Gets the Text matched by the group with the provided identifier, or
@@ -186,10 +186,10 @@ type Match_2
 
        In this case, the group id for "(d)", which is 3, is a valid group id and
        (Pattern_2.lookup_group 3) will return 3. If the caller tries to get 
-       group 3, Match_2.group will return the default value.
+       group 3, Match_2.text will return the default value.
     text : Integer | Text -> Any -> Text ! No_Such_Group
     text self group=0 ~default=Nothing =
-        result = self.grapheme_span group Nothing
+        result = self.span group Nothing
         if result.is_nothing then default else result.text
 
     ## Gets a vector containing the Text of _all_ of the capturing groups in
@@ -208,6 +208,16 @@ type Match_2
          If the regex contained named groups, these may also be accessed by
          index based on their position in the pattern.
 
+       Note that it is possible for a group to "not participate in the match",
+       for example with a disjunction. In the example below, the "(d)" group
+       does not participate -- it neither matches nor fails.
+
+            "ab((c)|(d))".find "abc"
+
+       In this case, the group id for "(d)", which is 3, is a valid group id and
+       (Pattern_2.lookup_group 3) will return 3. `groups` will return the
+       default value for groups that do not participate.
+
        > Example
          Get a vector of the text matched by all of the groups in this match,
          replacing the value for groups that didn't match with "UNMATCHED".
@@ -237,8 +247,8 @@ type Match_2
             "ab((c)|(d))".find "abc"
 
        In this case, the group id for "(d)", which is 3, is a valid group id and
-       (Pattern_2.lookup_group 3) will return 3. If the caller tries to get group 3,
-       Match_2.group will return the default value.
+       (Pattern_2.lookup_group 3) will return 3. `named_groups` will map
+       a named group that does not participate to the default value.
 
        > Example
          Get the map of all of the named groups in this match, replacing the
@@ -261,7 +271,7 @@ type Match_2
        Arguments:
        - id: The integer index or name of that group.
        - if_missing: The value to return if the index is out of bounds.
-    get : Integer -> Any -> Any
+    get : Integer -> Any -> Text | Any
     get self index ~if_missing=Nothing =
         self.text index . catch No_Such_Group (_-> if_missing)
 
@@ -272,6 +282,6 @@ type Match_2
        Arguments:
        - id: The integer index or name of that group.
        - if_missing: The value to return if the index is out of bounds.
-    at : Integer -> Any ! Index_Out_Of_Bounds
+    at : Integer -> Text ! Index_Out_Of_Bounds
     at self index =
         self.get index if_missing=(Error.throw (Index_Out_Of_Bounds.Error index self.pattern.group_count))

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Text/Regex/Pattern_2.enso

@@ -6,17 +6,19 @@ import project.Data.Range.Range
 import project.Data.Text.Span.Span
 import project.Data.Text.Span.Utf_16_Span
 import project.Data.Text.Regex.Match_2.Match_2
+import project.Data.Text.Regex.Replacer.Replacer
 import project.Data.Text.Regex_2.No_Such_Group
 import project.Data.Text.Text
 import project.Data.Vector.Vector
 import project.Error.Error
+import project.Errors.Illegal_Argument.Illegal_Argument
 import project.Meta
 import project.Nothing.Nothing
-import project.Panic.Panic
 import project.Polyglot.Polyglot
 
 from project.Data.Boolean import Boolean, True, False
 
+polyglot java import org.enso.base.Replacer_Cache
 polyglot java import org.enso.base.Text_Utils
 
 type Pattern_2
@@ -50,13 +52,15 @@ type Pattern_2
 
     ## Tries to match the provided `input` against the pattern `self`.
 
-       Returns a `Vector Match_2` objects, each containing the matched text
+       Returns a `Vector Match_2` object, each containing the matched text
        and its match groups.
 
        Arguments:
        - input: The text to match the pattern described by `self` against.
-    match_all : Text -> Vector Match_2
+    match_all : Text -> Vector Match_2 ! Illegal_Argument
     match_all self input =
+        pattern_is_empty = self.internal_regex_object.pattern == ''
+        if pattern_is_empty then Error.throw (Illegal_Argument.Error "Cannot run match_all with an empty pattern") else
             builder = Vector.new_builder
             it = Match_Iterator.new self input
             go it = case it.next of
@@ -89,6 +93,82 @@ type Pattern_2
     find_all self input =
         self.match_all input . map match_to_group_maybe
 
+    ## ADVANCED
+
+       Replace all occurrences of the pattern described by `self` in the `input`
+       with the specified `replacement`.
+
+       Arguments:
+       - input: The text in which to perform the replacement(s).
+       - replacement: The literal text with which to replace any matches.
+       - only_first: If True, only replace the first match.
+
+       If this method performs no replacements it will return the `input` text
+       unchanged.
+
+       The replacement string can contain references to groups matched by the
+       regex. The following syntaxes are supported:
+           $0: the entire match string
+           $&: the entire match string
+           $n: the nth group
+           $<foo>: Named group `foo`
+
+       > Example
+         Replace letters in the text "aa".
+
+             pattern = Regex_2.compile 'aa'
+             pattern.replace 'aaa' 'b' == 'ba'
+
+       > Example
+         Replace all occurrences of letters 'l' and 'o' with '#'.
+
+              pattern = Regex_2.compile '[lo]'
+              pattern.replace 'Hello World!' '#' == 'He### W#r#d!'
+
+       > Example
+         Replace the first occurrence of letter 'l' with '#'.
+
+             pattern = Regex_2.compile 'l'
+             pattern.replace 'Hello World!' '#' only_first=True == 'He#lo World!'
+
+       > Example
+         Replace texts in quotes with parentheses.
+
+              pattern = Regex_2.compile '"(.*?)"'
+              pattern.replace '"abc" foo "bar" baz' '($1)' == '(abc) foo (bar) baz'
+
+       > Example
+         Replace a literal string with a replacement value.
+
+             pattern = Regex_2.compile "aa"
+             input = "aa ab aa ac ad aa aa ax"
+             match = pattern.replace input "xyz"
+             match == "xyz ab xyz ac ad xyz xyz ax"
+
+       > Example
+         Replace each word with the same word surrounded by `[]`.
+
+             pattern = Regex_2.compile "([a-z]+)"
+             pattern.replace "foo bar, baz" "[$1]" == "[foo] [bar], [baz]"
+
+    replace : Text -> Text -> Boolean -> Text
+    replace self input replacement only_first=False =
+        it = Match_Iterator.new self input
+        case it of
+            Match_Iterator_Value.Last filler -> filler.text
+            _ ->
+                replacer = Replacer.new replacement self
+
+                replacer.if_not_error <|
+                    go next current = case next of
+                        Match_Iterator_Value.Next filler match next_it ->
+                            new_value = current + filler.text + (replacer.replace match)
+                            next = if only_first then next_it.early_exit else next_it.next
+                            @Tail_Call go next new_value
+                        Match_Iterator_Value.Last filler ->
+                            current + filler.text
+                    go it.next ""
+
     ## PRIVATE
 
        Look up a match group name or number, and check that it is valid.
@@ -106,6 +186,9 @@ type Pattern_2
        A group name is an alias for a group number; if a name is passed to
        this method, it returns the corresponding group number.
 
+       If a group number is passed to `lookup_group` and it is valid, it will
+       simply return the group number.
+
        Note that it is possible for a group to "not participate in the match",
        for example with a disjunction. In the example below, the "(d)" group
        does not participate -- it neither matches nor fails.
@@ -138,6 +221,15 @@ type Pattern_2
                     _ : Integer -> n
                     Nothing -> Error.throw (No_Such_Group.Error name)
 
+    ## PRIVATE
+
+       Return a lazy iterator over matches against a string.
+
+       Arguments
+       - text: the string to match against.
+    iterator : Text -> Match_Iterator
+    iterator self input = Match_Iterator.new self input
+
     ## Return the number of groups in the underlying RegexObject.
        Note, the count includes group 0 (the whole match) as well.
     group_count : Integer
@@ -154,32 +246,51 @@ type Pattern_2
     Performs the regex match, and iterates through the results. Yields both
     the matched parts of the string, and the 'filler' parts between them.
 
+    The 'filler' elements are `Utf_16_Span`s, not `Spans`. This is because
+    matches and replacement boundaries can fall in the middle of multi-
+    character graphemes, thereby splitting them apart.
+
     At each step, it yields a Match_Iterator_Value, whivch has either a filler
     and a match, or just the final filler. A Match_Iterator_Value.Last value is
     return at the end, and only at the end.
+
+    Optionally, you can call `early_exit` to have it return the remainder of
+    the string, unmatched, as a single Last value. (Used for `replace` with
+    `only_first=True`.)
 type Match_Iterator
     new : Pattern_2 -> Text -> Match_Iterator
     new pattern input = Match_Iterator.Value pattern input 0
 
     Value (pattern : Pattern_2) (input : Text) (cursor : Integer)
 
+    ## Return the next match, or the last filler string if there is no
+       additional match.
+
+       Also returns the next iterator, if there was a match.
     next : Match_Iterator_Value
     next self =
         regex_result = self.pattern.internal_regex_object.exec self.input self.cursor
         case regex_result.isMatch of
             False ->
                 filler_range = Range.new self.cursor (Text_Utils.char_length self.input)
-                filler_span = (Utf_16_Span.Value filler_range self.input).to_grapheme_span
+                filler_span = (Utf_16_Span.Value filler_range self.input)
                 Match_Iterator_Value.Last filler_span
             True ->
                 match_start = regex_result.getStart 0
                 filler_range = Range.new self.cursor match_start
-                filler_span = (Utf_16_Span.Value filler_range self.input).to_grapheme_span
+                filler_span = (Utf_16_Span.Value filler_range self.input)
                 match = Match_2.Value self.pattern regex_result self.input
-                next_cursor = match.utf16_end 0
+                next_cursor = match.utf_16_end 0
                 next_iterator = Match_Iterator.Value self.pattern self.input next_cursor
                 Match_Iterator_Value.Next filler_span match next_iterator
 
+    ## Returns the remainder of the string, unmatched.
+    early_exit : Match_Iterator_Value
+    early_exit self =
+        filler_range = Range.new self.cursor (Text_Utils.char_length self.input)
+        filler_span = Utf_16_Span.Value filler_range self.input
+        Match_Iterator_Value.Last filler_span
+
     to_text_debug : Vector Text
     to_text_debug self =
         vb = Vector.new_builder

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Text/Regex/Replacer.enso

@@ -0,0 +1,144 @@
+import project.Data.Numbers.Integer
+import project.Data.Text.Extensions
+import project.Data.Text.Regex.Match_2.Match_2
+import project.Data.Text.Regex.Pattern_2.Match_Iterator_Value
+import project.Data.Text.Regex.Pattern_2.Pattern_2
+import project.Data.Text.Regex_2
+import project.Data.Text.Regex_2.No_Such_Group
+import project.Data.Text.Span.Utf_16_Span
+import project.Data.Text.Text
+import project.Data.Vector.Vector
+import project.Error.Error
+import project.Errors.Illegal_State.Illegal_State
+import project.Nothing.Nothing
+import project.Panic.Panic
+
+from project.Data.Boolean import Boolean, True, False
+
+polyglot java import java.lang.StringBuilder
+polyglot java import org.enso.base.Replacer_Cache
+
+type Replacer
+    ## PRIVATE
+
+       Implements a replacement for a regular expression.
+
+       Pattern_2.replace uses a Replacer to replace each regex match with
+       a replacement string. This string can contain references to match
+       groups from the original regex.
+
+       The `new` smart constructor parses a Text into a vector of
+       Replacements. Each Replacement is either a literal string or a
+       group number. To provide a replacement for a regex match, the
+       Replacer iterates through the Replacement vector, substitutes
+       the match group contents for each group number, and concatenates
+       all the strings together to form the full replacement string.
+    Value (replacement : Vector Replacement)
+
+    ## Creates a new Replacer.
+
+       Arguments
+       - replacement_string: a string, possibly containing group references,
+         that will be used to provide a replacement in a regex match.
+    new : Text -> Pattern_2 -> Replacer ! No_Such_Group
+    new replacement_string pattern =
+        Replacer.Value (build_replacement_vector_cached replacement_string pattern)
+
+    ## Build a replacement string from a match.
+
+       Arguments:
+       - match: the match from the original string that is to be replaced.
+    replace : Match_2 -> Text
+    replace self match =
+        string_builder = StringBuilder.new
+        self.replacement.each replacement->
+            s = case replacement of
+                Replacement.Literal text -> text
+                Replacement.Substitution group_number -> match.text group_number
+            string_builder.append s
+        string_builder.toString
+
+## PRIVATE
+
+   Get the size of the Replacer LRU cache. For testing.
+get_lru_size : Integer
+get_lru_size = Replacer_Cache.getLruSize
+
+## PRIVATE
+
+   Look up a replacement string in the Replacer LRU cache. For testing.
+replacer_cache_lookup : Text -> Replacer | Nothing
+replacer_cache_lookup replacement_string = Replacer_Cache.get replacement_string
+
+## PRIVATE
+group_reference_regex = "\$(([0-9]+)|(\$)|(&)|(<([^>]+)>))"
+
+## PRIVATE
+
+   Build a replacement vector.
+
+   Parse the replacement string into an alternating series of literal
+   strings and group reference numbers.
+
+   Uses Replacement_Cache to avoid rebuilding the vector for recently used
+   replacement strings.
+build_replacement_vector_cached : Text -> Pattern_2 -> Vector Replacement ! No_Such_Group
+build_replacement_vector_cached replacement_string pattern =
+    Replacer_Cache.get_or_set replacement_string _->
+        build_replacement_vector replacement_string pattern
+
+## PRIVATE
+
+   Build a replacement vector.
+
+   Parse the replacement string into an alternating series of literal
+   strings and group reference numbers.
+build_replacement_vector : Text -> Pattern_2 -> Vector Replacement ! No_Such_Group
+build_replacement_vector replacement_string pattern =
+    replacement_pattern = Regex_2.compile group_reference_regex
+    it = replacement_pattern.iterator replacement_string
+
+    builder = Vector.new_builder
+    go it = case it.next of
+        Match_Iterator_Value.Next filler match next_it ->
+            replacement = parse_group_number pattern match
+            replacement.if_not_error <|
+                builder.append (Replacement.Literal filler.text)
+                builder.append replacement
+                @Tail_Call go next_it
+        Match_Iterator_Value.Last filler ->
+            builder.append (Replacement.Literal filler.text)
+    result = go it
+    result.if_not_error <|
+        builder.to_vector
+
+## PRIVATE
+
+   Parse a capture group reference.
+
+   Arguments:
+   - pattern: the Pattern_2 used to initiate the replacement. This is used
+     to identify and validate capture groups.
+   - match: the match of the replacement string against group_reference_regex.
+
+   Returns a Replacement: a group number, or, in the case of `$$`, a literal.
+
+   See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
+parse_group_number : Pattern_2 -> Match_2 -> Replacement ! No_Such_Group
+parse_group_number pattern match = case match.text.take 2 of
+    "$$" -> Replacement.Literal "$"
+    "$<" ->
+        # Group 6 contains the group name without the `<>`.
+        group_name = match.text 6
+        Replacement.Substitution (pattern.lookup_group group_name)
+    "$&" -> Replacement.Substitution 0
+    _ -> 
+        n = Integer.parse <| match.text 2
+        Replacement.Substitution (pattern.lookup_group n)
+
+type Replacement
+    ## A string literal to replace with.
+    Literal (text : Text)
+
+    ## Target group to insert.
+    Substitution (group_number : Integer)

distribution/lib/Standard/Base/0.0.0-dev/src/Data/Text/Regex_2.enso

@@ -7,6 +7,7 @@ import project.Error.Error
 import project.Errors.Illegal_Argument.Illegal_Argument
 import project.Nothing.Nothing
 import project.Panic.Panic
+
 from project.Data.Boolean import Boolean, True, False
 from project.Errors.Common import Syntax_Error
 
@@ -17,18 +18,21 @@ polyglot java import java.util.regex.Pattern as Java_Pattern
 
    Arguments
    - expression: The text representing the regular expression that you want to
-     compile.
+     compile. Must be non-empty.
    - case_insensitive: Enables or disables case-insensitive matching. Case
      insensitive matching behaves as if it normalises the case of all input
      text before matching on it.
 
+   If an empty regex is used, `compile` throws an Illegal_Argument error.
+
    ? Why Compile?
      While many regex engines are able to cache ad-hoc patterns, it is often
      useful to be able to manually retain a pattern that you have computed. This
      function exists so you can hold onto the resultant `Pattern_2` object,
      instead of immediately proceeding to match using it.
-compile : Text -> Boolean | Nothing -> Pattern_2 ! Regex_Syntax_Error
+compile : Text -> Boolean | Nothing -> Pattern_2 ! Regex_Syntax_Error | Illegal_Argument
 compile self expression case_insensitive=Nothing =
+    if expression == '' then Error.throw (Illegal_Argument.Error "Regex cannot be the empty string") else
         options_string = if case_insensitive == True then "usgi" else "usg"
 
         internal_regex_object = Panic.catch Syntax_Error (Prim_Text_Helper.compile_regex expression options_string) caught_panic->

distribution/lib/Standard/Table/0.0.0-dev/src/Data/Table.enso

@@ -843,8 +843,8 @@ type Table
             parse_problem_builder.attach_problems_before on_problems <|
                 Table.new new_columns
 
-    ## Replaces the first, last, or all occurrences of `term` with
-       `new_text` in each text row of selected columns.
+    ## Replaces the first, or all occurrences of `term` with `new_text` in each
+       text row of selected columns.
        If `term` is empty, the function returns the table unchanged.
 
        This method follows the exact replacement semantics of the
@@ -854,15 +854,13 @@ type Table
        - columns: Column selection criteria or a column name or index.
        - term: The term to find.
        - new_text: The new text to replace occurrences of `term` with.
-         If `matcher` is a `Regex_Matcher`, `new_text` can include replacement
-         patterns (such as `$<n>`) for a marked group.
-       - mode: Specifies which occurences of term the engine tries to find. When the
-         mode is `First` or `Last`, this method replaces the first or last occurence
-         of term in each individual table cell. If set to `All`, it replaces all
-         occurences of term.
-       - matcher: If a `Text_Matcher`, the text is compared using case-sensitivity
-         rules specified in the matcher. If a `Regex_Matcher`, the term is used as a
-         regular expression and matched using the associated options.
+         If use_regex is true, `new_text` can include replacement patterns
+         (such as `$<n>`) for a marked group.
+       - case_insensitive: Enables or disables case-insensitive matching. Case
+         insensitive matching behaves as if it normalises the case of all input
+         text before matching on it.
+       - only_first: If True, only replace the first match.
+       - use_regex: If true, the term is used as a regular expression.
        - on_problems: Specifies how to handle if a problem occurs, raising as a
          warning by default.
 
@@ -881,21 +879,21 @@ type Table
        > Example
          Remove leading and trailing spaces from cells in multiple columns.
 
-             table.replace_text By_Name ["foo", "bar"] "^\s*(.*?)\s*$" "$1" matcher=Regex_Matcher.Value
+             table.replace_text By_Name ["foo", "bar"] "^\s*(.*?)\s*$" "$1" use_regex=True
 
        > Example
          Replace texts in quotes with parentheses in column at index 1.
 
-             table.replace_text 1 '"(.*?)"' '($1)' matcher=Regex_Matcher.Value
-    replace_text : Text | Integer | Column_Selector | Vector (Integer | Text | Column_Selector) -> Text -> Text -> Matching_Mode | Regex_Mode -> (Text_Matcher | Regex_Matcher) -> Problem_Behavior -> Table
-    replace_text self columns=[0] term="" new_text="" mode=Regex_Mode.All matcher=Text_Matcher.Case_Sensitive on_problems=Problem_Behavior.Report_Warning = if term.is_empty then self else
+             table.replace_text 1 '"(.*?)"' '($1)' use_regex=True
+    replace_text : Text | Integer | Column_Selector | Vector (Integer | Text | Column_Selector) -> Text -> Text -> Case_Sensitivity -> Boolean -> Boolean -> Problem_Behavior -> Table
+    replace_text self columns=[0] term="" new_text="" case_sensitivity=Case_Sensitivity.Sensitive only_first=False use_regex=False on_problems=Problem_Behavior.Report_Warning = if term.is_empty then self else
         problem_builder = Problem_Builder.new
 
         selection = self.columns_helper.select_columns_helper columns reorder=False problem_builder
         selected_names = Map.from_vector (selection.map column-> [column.name, True])
 
         map_preserve_name column f = column.map f . rename column.name
-        do_replace = _.replace term new_text mode matcher
+        do_replace = _.replace term new_text case_sensitivity=case_sensitivity only_first=only_first use_regex=use_regex
         do_replace_only_text = case _ of
                 item : Text -> do_replace item
                 item -> item

distribution/lib/Standard/Table/0.0.0-dev/src/Internal/Naming_Helpers.enso

@@ -18,7 +18,7 @@ type Naming_Helpers
     sanitize_name : Text -> Text
     sanitize_name name =
         # Using the regex matcher due to the #5831 bug.
-        name.replace '\0' '\\\\0' matcher=Regex_Matcher.Value
+        name.replace '\0' '\\0' use_regex=True
 
     ## PRIVATE
        Generates a column name for a binary operation.

std-bits/base/src/main/java/org/enso/base/Replacer_Cache.java

@@ -0,0 +1,51 @@
+package org.enso.base;
+
+import org.graalvm.collections.Pair;
+import org.graalvm.polyglot.Value;
+
+import java.util.ArrayList;
+import java.util.function.Function;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class Replacer_Cache {
+  private static final int lruSize = 5;
+
+  // Circular buffer containing the most recent cache keys.
+  private static final List<Pair<String, Value>> lru = new ArrayList<>(lruSize);
+
+  static {
+    for (int i = 0; i < lruSize; ++i) {
+      lru.add(null);
+    }
+  }
+
+  // Index into the circular buffer.
+  private static int nextSlot = 0;
+
+  public static Value get_or_set(String key, Function<Void, Value> value_producer) {
+    Value value = get(key);
+    if (value == null) {
+      value = value_producer.apply(null);
+      lru.set(nextSlot, Pair.create(key, value));
+      nextSlot = (nextSlot + 1) % lruSize;
+    }
+    return value;
+  }
+
+  // Visible for testing.
+  public static Value get(String key) {
+    for (int i = 0; i < lruSize; ++i) {
+      Pair<String, Value> pair = lru.get(i);
+      if (pair != null && pair.getLeft().equals(key)) {
+        return lru.get(i).getRight();
+      }
+    }
+    return null;
+  }
+
+  public static int getLruSize() {
+    return lruSize;
+  }
+}

test/Table_Tests/src/In_Memory/Table_Spec.enso

@@ -644,7 +644,7 @@ spec =
             bools = ["bools", [False, False, True, True]]
             texts = ["texts", ["foo", "bar", "baz", "spam"]]
             table = Table.new [bools, texts]
-            actual = table.replace_text "texts" "(a|o)" "$1e" matcher=Regex_Matcher.Value
+            actual = table.replace_text "texts" "(a|o)" "$1e" use_regex=True
             actual.at "texts" . to_vector . should_equal ["foeoe", "baer", "baez", "spaem"]
             Problems.assume_no_problems actual
 

test/Tests/src/Data/Text/Regex_2_Spec.enso

@@ -1,199 +1,98 @@
 from Standard.Base import all
+import Standard.Base.Data.Text.Span.Span
 import Standard.Base.Data.Text.Span.Utf_16_Span
-import Standard.Base.Data.Text.Regex_2
 import Standard.Base.Data.Text.Regex.Match_2.Match_2
+import Standard.Base.Data.Text.Regex.Pattern_2.Pattern_2
+import Standard.Base.Data.Text.Regex.Replacer.Replacer
+import Standard.Base.Data.Text.Regex_2
 import Standard.Base.Data.Text.Regex_2.No_Such_Group
 import Standard.Base.Data.Text.Regex_2.Regex_Syntax_Error
+import Standard.Base.Errors.Illegal_Argument.Illegal_Argument
+
+from Standard.Base.Data.Text.Regex.Replacer import get_lru_size, replacer_cache_lookup
 
 from Standard.Test import Test, Test_Suite
 import Standard.Test.Extensions
 
-# default_mask = Java_Pattern.CANON_EQ.bit_or Java_Pattern.UNICODE_CASE . bit_or Java_Pattern.UNICODE_CHARACTER_CLASS
+polyglot java import org.enso.base.Replacer_Cache
 
 spec =
-    ##
-        Test.group "The default regex engine's options handling" <|
+    Test.group "Compile" <|
+        Test.specify "should be able to be compiled" <|
+            pattern = Regex_2.compile "(?<dots>..)" case_insensitive=True
+            pattern . should_be_a Pattern_2
 
-            Test.specify "should convert options to Java" <|
-                options = [Regex_Option.Comments, Regex_Option.Multiline, Default_Engine.Option.Unix_Lines]
-                expected_mask = Java_Pattern.UNIX_LINES.bit_or Java_Pattern.COMMENTS . bit_or Java_Pattern.MULTILINE . bit_or default_mask
-                actual_mask = Default_Engine.from_enso_options options
+        Test.specify "should throw Regex_Syntax_Error for a regex with incorrect syntax" <|
+            Regex_2.compile "ab(c(((((((" . should_fail_with Regex_Syntax_Error
 
-                actual_mask . should_equal expected_mask
-
-            Test.specify "should specify the unicode options by default" <|
-                actual_mask = Default_Engine.from_enso_options []
-
-                actual_mask . should_equal default_mask
-
-            Test.specify "should handle ascii matching by disabling unicode" <|
-                actual_mask = Default_Engine.from_enso_options [Regex_Option.Ascii_Matching]
-                actual_mask . should_equal 0
-
-            Test.specify "should result in an error when an option is invalid" <|
-                Default_Engine.from_enso_options [""] . should_fail_with Invalid_Option
-                Default_Engine.from_enso_options ["", Regex_Option.Ascii_Matching] . should_fail_with Invalid_Option
-
-        Test.group "The default regex engine (Default_Engine)" <|
-
-            Test.specify "should be able to compile patterns with no options" <|
-                engine = Default_Engine.new
-                pattern = engine.compile "^a$" []
-                pattern.engine . should_equal engine
-                pattern.options . should_equal []
-                pattern.internal_pattern.flags . should_equal default_mask
-
-            Test.specify "should be able to compile patterns with global options" <|
-                engine = Default_Engine.new
-                pattern = engine.compile "^a$" [Regex_Option.Multiline]
-                pattern.engine . should_equal engine
-                pattern.options . should_equal [Regex_Option.Multiline]
-                pattern.internal_pattern.flags . should_equal (default_mask.bit_or Java_Pattern.MULTILINE)
-
-            Test.specify "should be able to compile patterns with engine-specific options" <|
-                engine = Default_Engine.new [Default_Engine.Option.Literal_Pattern]
-                pattern = engine.compile "^a$" []
-                pattern.engine . should_equal engine
-                pattern.options . should_equal [Default_Engine.Option.Literal_Pattern]
-                pattern.internal_pattern.flags . should_equal (default_mask.bit_or Java_Pattern.LITERAL)
-
-            Test.specify "should be able to compile patterns with combined options" <|
-                engine = Default_Engine.new [Default_Engine.Option.Literal_Pattern]
-                pattern = engine.compile "^a$" [Regex_Option.Comments]
-                pattern.engine . should_equal engine
-                pattern.options.contains Default_Engine.Option.Literal_Pattern . should_be_true
-                pattern.options.contains Regex_Option.Comments . should_be_true
-                pattern.internal_pattern.flags . should_equal (default_mask . bit_or Java_Pattern.LITERAL . bit_or Java_Pattern.COMMENTS)
-
-            Test.specify "should return a syntax error of the regex syntax is invalid" <|
-                engine = Default_Engine.new
-                engine.compile "^(a" [] . should_fail_with Syntax_Error
-
-            Test.specify "should throw an invalid options error if an option is invalid" <|
-                engine = Default_Engine.new
-                engine.compile "^a$" ["invalid"] . should_fail_with Invalid_Option
+        Test.specify "should disallow empty patterns in `compile`" <|
+            Regex_2.compile "" . should_fail_with Illegal_Argument
 
+    Test.group "Escape" <|
         Test.specify "should escape an expression for use as a literal" <|
             pattern = "http://example.com"
-                engine = Default_Engine.new
-                engine.escape pattern . should_equal "\Qhttp://example.com\E"
-
-        Test.group "The default regex engine's Pattern.matches" <|
-            engine = Default_Engine.new
+            Regex_2.escape pattern . should_equal "\Qhttp://example.com\E"
 
+    Test.group "Pattern.matches" <|
         Test.specify "should return True when the pattern matches against the input" <|
-                pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+            pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
             input = "aa ab abc a bc bcd"
             pattern.matches input . should_be_true
 
         Test.specify "should return False when the pattern doesn't match against the input" <|
-                pattern = engine.compile "aaz" []
+            pattern = Regex_2.compile "aaz"
             input = "aa ab abc a bc bcd"
             pattern.matches input . should_be_false
 
         Test.specify "should check for full matches" <|
-                pattern = engine.compile "f.o" []
+            pattern = Regex_2.compile "f.o"
             pattern.matches "foo" . should_be_true
             pattern.matches "foobar" . should_be_false
 
-        Test.group "The default regex engine's Pattern.match" <|
-            engine = Default_Engine.new
+        Test.specify "`matches` with an empty pattern should be an error" <|
+            pattern = Regex_2.compile ""
+            pattern.matches "ABC" . should_fail_with Illegal_Argument
 
+    Test.group "Pattern.match" <|
         Test.specify "should be able to `match` the first instance of the pattern in the input" <|
-                pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+            pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
             input = "aa ab abc a bc bcd"
-                match = pattern.match input mode=Matching_Mode.First
-                match . should_be_a Default_Engine.Match.Value
+            match = pattern.match input
+            match . should_be_a Match_2
             match.text 0 . should_equal input
 
         Test.specify "should return `Nothing` if there are no matches in first mode" <|
-                pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+            pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
             input = "abc"
-                match = pattern.match input mode=Matching_Mode.First
-                match . should_equal Nothing
-
-            Test.specify "should be able to `match` at most N instances of the pattern in the input" <|
-                pattern = engine.compile "(..)" []
-                input = "abcdefghij"
-                match = pattern.match input mode=3
-                match.length . should_equal 3
-                match.at 0 . group 0 . should_equal "ab"
-                match.at 1 . group 0 . should_equal "cd"
-                match.at 2 . group 0 . should_equal "ef"
-
-            Test.specify "should `match` fewer than N instances when there are fewer than N in the input" <|
-                pattern = engine.compile "(..)" []
-                input = "abcdef"
-                match = pattern.match input mode=5
-                match.length . should_equal 3
-                match.at 0 . group 0 . should_equal "ab"
-                match.at 1 . group 0 . should_equal "cd"
-                match.at 2 . group 0 . should_equal "ef"
-
-            Test.specify "should return `Nothing` when a counted match fails" <|
-                pattern = engine.compile "(aa)" []
-                input = "abcdefghij"
-                match = pattern.match input mode=3
+            match = pattern.match input
             match . should_equal Nothing
 
         Test.specify "should be able to `match` the all instances of the pattern in the input" <|
-                pattern = engine.compile "(..)" []
+            pattern = Regex_2.compile "(..)"
             input = "abcdefghij"
-                match = pattern.match input mode=Regex_Mode.All
-                match.length . should_equal 5
-                match.at 0 . group 0 . should_equal "ab"
-                match.at 1 . group 0 . should_equal "cd"
-                match.at 2 . group 0 . should_equal "ef"
-                match.at 3 . group 0 . should_equal "gh"
-                match.at 4 . group 0 . should_equal "ij"
+            matches = pattern.match_all input
+            matches.length . should_equal 5
+            matches.at 0 . text 0 . should_equal "ab"
+            matches.at 1 . text 0 . should_equal "cd"
+            matches.at 2 . text 0 . should_equal "ef"
+            matches.at 3 . text 0 . should_equal "gh"
+            matches.at 4 . text 0 . should_equal "ij"
 
-            Test.specify "should return `Nothing` when an all match match fails" <|
-                pattern = engine.compile "(aa)" []
+        Test.specify "should return `[]` when an all match match fails" <|
+            pattern = Regex_2.compile "(aa)"
             input = "abcdefghij"
-                match = pattern.match input mode=Regex_Mode.All
-                match . should_equal Nothing
+            match = pattern.match_all input
+            match . should_equal []
 
-            Test.specify "should be able to `match` the pattern against the entire input" <|
-                pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
-                input = "aa ab abc a bc bcd"
-                match = pattern.match input mode=Regex_Mode.Full
-                match . should_be_a Default_Engine.Match.Value
-                match.text 0 . should_equal input
+        Test.specify "`match` with an empty pattern should be an error" <|
+            pattern = Regex_2.compile ""
+            pattern.match "ABC" . should_fail_with Illegal_Argument
 
-            Test.specify "should return `Nothing` if a full match does not match the entire input" <|
-                pattern = engine.compile "(..)" []
-                input = "aa ab"
-                full_match = pattern.match input mode=Regex_Mode.Full
-                full_match . should_equal Nothing
-                match = pattern.match input mode=Matching_Mode.First
-                match . should_be_a Default_Engine.Match.Value
+        Test.specify "`match_all` with an empty pattern should be an error" <|
+            pattern = Regex_2.compile ""
+            pattern.match_all "ABC" . should_fail_with Illegal_Argument
 
-            Test.specify "should be able to `match` the pattern against bounded input" <|
-                pattern = engine.compile "(..)" []
-                input = "abcdefghij"
-                match = pattern.match input mode=(Regex_Mode.Bounded 2 8)
-                match.length . should_equal 3
-                match.at 0 . text 0 . should_equal "cd"
-                match.at 1 . text 0 . should_equal "ef"
-                match.at 2 . text 0 . should_equal "gh"
-
-            Test.specify "should correctly handle empty patterns" pending="Figure out how to make Regex correctly handle empty patterns." <|
-               pattern = engine.compile "" []
-               match_1 = pattern.match "" mode=Regex_Mode.All
-               match_1.length . should_equal 1
-               match_1.at 0 . start 0 . should_equal 0
-               match_1.at 0 . end 0 . should_equal 0
-
-               match_2 = pattern.match "ABC" mode=Regex_Mode.All
-               match_2.length . should_equal 4
-               match_2.at 0 . start 0 . should_equal 0
-               match_2.at 0 . end 0 . should_equal 0
-               match_2.at 1 . start 0 . should_equal 1
-               match_2.at 1 . end 0 . should_equal 1
-               match_2.at 3 . start 0 . should_equal 3
-               match_2.at 3 . end 0 . should_equal 3
-
-    Test.group "The default regex engine's Pattern.find" <|
+    Test.group "Pattern_2.find and .find_all" <|
         Test.specify "should be able to `find` the first instance of the pattern in the input" <|
             pattern = Regex_2.compile "(..)"
             input = "abcdefghij"
@@ -229,6 +128,14 @@ spec =
             Regex_2.compile "([a]+|[1]+)" . find_all "a1a1" . should_equal ["a", "1", "a", "1"]
             Regex_2.compile "([0-9]+|[^0-9]+)" . find_all "a1b2" . should_equal ["a", "1", "b", "2"]
 
+        Test.specify "`find` with an empty pattern should be an error" <|
+            pattern = Regex_2.compile ""
+            pattern.find "ABC" . should_fail_with Illegal_Argument
+
+        Test.specify "`find_all` with an empty pattern should be an error" <|
+            pattern = Regex_2.compile ""
+            pattern.find_all "ABC" . should_fail_with Illegal_Argument
+
     ##
         Test.group "The default regex engine's Pattern.split" <|
             engine = Default_Engine.new
@@ -279,142 +186,122 @@ spec =
                 match.at 3 . should_equal "e"
                 match.at 4 . should_equal "f"
 
-        Test.group "The default regex engine's Pattern.replace" <|
-            engine = Default_Engine.new
-
+    Test.group "Pattern_2.replace" <|
         Test.specify "should be able to `replace` the first instance of the pattern in the input" <|
-                pattern = engine.compile "abc" []
+            pattern = Regex_2.compile "abc"
             input = "aa ab abc a bc abc"
-                match = pattern.replace input "REPLACED" mode=Matching_Mode.First
+            match = pattern.replace input "REPLACED" only_first=True
             match . should_be_a Text
             match . should_equal "aa ab REPLACED a bc abc"
 
-            Test.specify "should return the string unchanged if there are no matches to replace in first mode" <|
-                pattern = engine.compile "xyz" []
+        Test.specify "should return the string unchanged if there are no matches to replace in only_first mode" <|
+            pattern = Regex_2.compile "xyz"
             input = "aa ab ac ad"
-                match = pattern.replace input "REPLACED" mode=Matching_Mode.First
-                match . should_equal input
-
-            Test.specify "should be able to replace at most N instances of the pattern in the input" <|
-                pattern = engine.compile "aa" []
-                input = "aa ab aa ac ad aa aa ax"
-                match = pattern.replace input "REPLACED" mode=3
-                match . should_equal "REPLACED ab REPLACED ac ad REPLACED aa ax"
-
-            Test.specify "should replace fewer than N instances when there are fewer than N in the input" <|
-                pattern = engine.compile "aa" []
-                input = "aa ab aa ac ad aa aa ax"
-                match = pattern.replace input "REPLACED" mode=10
-                match . should_equal "REPLACED ab REPLACED ac ad REPLACED REPLACED ax"
-
-            Test.specify "should return the input when a counted replace fails" <|
-                pattern = engine.compile "aa" []
-                input = "abcdefghij"
-                match = pattern.replace input "REPLACED" mode=3
+            match = pattern.replace input "REPLACED" only_first=True
             match . should_equal input
 
         Test.specify "should be able to replace the all instances of the pattern in the input" <|
-                pattern = engine.compile "aa" []
+            pattern = Regex_2.compile "aa"
             input = "aa ab aa ac ad aa aa ax"
-                match = pattern.replace input "REPLACED" mode=Regex_Mode.All
+            match = pattern.replace input "REPLACED"
             match . should_equal "REPLACED ab REPLACED ac ad REPLACED REPLACED ax"
 
         Test.specify "should return the input when an all replace fails" <|
-                pattern = engine.compile "aa" []
+            pattern = Regex_2.compile "aa"
             input = "abcdefghij"
-                match = pattern.replace input "REPLACED" mode=Regex_Mode.All
+            match = pattern.replace input "REPLACED"
             match . should_equal input
 
         Test.specify "should be able to replace the entire input only if it matches" <|
-                pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+            pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
             input = "aa ab abc a bc bcd"
-                match = pattern.replace input "REPLACED" mode=Regex_Mode.Full
+            match = pattern.replace input "REPLACED"
             match . should_equal "REPLACED"
 
-            Test.specify "should correctly replace entire input in Full mode even if partial matches are possible" <|
-                pattern = engine.compile "(aa)+" []
-                pattern.replace "aaa" "REPLACED" mode=Regex_Mode.Full . should_equal "aaa"
-                pattern.replace "aaaa" "REPLACED" mode=Regex_Mode.Full . should_equal "REPLACED"
-
-            Test.specify "should return the input for a full replace if the pattern doesn't match the entire input" <|
-                pattern = engine.compile "(..)" []
-                input = "aa ab"
-                full_match = pattern.replace input "REPLACED" mode=Regex_Mode.Full
-                full_match . should_equal input
-
-            Test.specify "should not perform overlapping replacements in counted mode" <|
-                pattern = engine.compile "(..)" []
-                input = "abcdefghij"
-                result = pattern.replace input "REPLACED" mode=3
-                result . should_equal "REPLACEDREPLACEDREPLACEDghij"
-
         Test.specify "should not perform overlapping replacements in all mode" <|
-                pattern = engine.compile "(..)" []
+            pattern = Regex_2.compile "(..)"
             input = "aa ab"
-                match = pattern.replace input "REPLACED" mode=Regex_Mode.All
+            match = pattern.replace input "REPLACED"
             match . should_equal "REPLACEDREPLACEDb"
 
         Test.specify "should handle capture groups in replacement" <|
-                pattern = engine.compile "(?<capture>[a-z]+)" []
-                pattern.replace "foo bar, baz" "[$1]" mode=Regex_Mode.All . should_equal "[foo] [bar], [baz]"
-                pattern.replace "foo bar, baz" "[$1]" mode=0 . should_equal "foo bar, baz"
-                pattern.replace "foo bar, baz" "[$1]" mode=1 . should_equal "[foo] bar, baz"
-                pattern.replace "foo bar, baz" "[$1]" mode=2 . should_equal "[foo] [bar], baz"
-                pattern.replace "foo bar, baz" "[$1]" mode=3 . should_equal "[foo] [bar], [baz]"
-                pattern.replace "foo bar, baz" "[$1]" mode=4 . should_equal "[foo] [bar], [baz]"
-                pattern.replace "foo bar, baz" "[$1]" mode=Matching_Mode.First . should_equal "[foo] bar, baz"
-                pattern.replace "foo bar, baz" "[$1]" mode=Matching_Mode.Last . should_equal "foo bar, [baz]"
+            pattern = Regex_2.compile "(?<capture>[a-z]+)"
+            pattern.replace "foo bar, baz" "[$1]" . should_equal "[foo] [bar], [baz]"
+            pattern.replace "foo bar, baz" "[$1]" only_first=True . should_equal "[foo] bar, baz"
 
-                pattern.replace "foo bar, baz" "[${capture}]" mode=Regex_Mode.All . should_equal "[foo] [bar], [baz]"
-                pattern.replace "foo bar, baz" "[${capture}]" mode=0 . should_equal "foo bar, baz"
-                pattern.replace "foo bar, baz" "[${capture}]" mode=1 . should_equal "[foo] bar, baz"
-                pattern.replace "foo bar, baz" "[${capture}]" mode=2 . should_equal "[foo] [bar], baz"
-                pattern.replace "foo bar, baz" "[${capture}]" mode=3 . should_equal "[foo] [bar], [baz]"
-                pattern.replace "foo bar, baz" "[${capture}]" mode=4 . should_equal "[foo] [bar], [baz]"
-                pattern.replace "foo bar, baz" "[${capture}]" mode=Matching_Mode.First . should_equal "[foo] bar, baz"
-                pattern.replace "foo bar, baz" "[${capture}]" mode=Matching_Mode.Last . should_equal "foo bar, [baz]"
+            pattern.replace "foo bar, baz" "[$<capture>]" . should_equal "[foo] [bar], [baz]"
+            pattern.replace "foo bar, baz" "[$<capture>]" only_first=True . should_equal "[foo] bar, baz"
 
-            Test.specify "should handle capture groups in replacement in All mode" <|
-                pattern = engine.compile "([a-z]+)" []
-                pattern.replace "foo bar, baz" "[$1]" mode=Regex_Mode.Full . should_equal "foo bar, baz"
-                pattern.replace "foo" "[$1]" mode=Regex_Mode.Full . should_equal "[foo]"
+            pattern.replace "foo bar, baz" "[$0]" . should_equal "[foo] [bar], [baz]"
+            pattern.replace "foo bar, baz" "[$0]" only_first=True . should_equal "[foo] bar, baz"
+            pattern.replace "foo bar, baz" "[$&]" . should_equal "[foo] [bar], [baz]"
+            pattern.replace "foo bar, baz" "[$&]" only_first=True . should_equal "[foo] bar, baz"
 
-                pattern_2 = engine.compile '<a href="(?<addr>.*?)">(?<name>.*?)</a>' []
-                pattern_2.replace '<a href="url">content</a>' "$2 <- $1" mode=Regex_Mode.Full . should_equal "content <- url"
-                pattern_2.replace '<a href="url">content</a>' "${name} <- ${addr}" mode=Regex_Mode.Full . should_equal "content <- url"
+        Test.specify "should handle unicode in capture group names" <|
+            pattern = Regex_2.compile "(?<건반>[a-z]+)"
+            pattern.replace "foo bar, baz" "[$<건반>]" . should_equal "[foo] [bar], [baz]"
 
-        Test.group "Match.group" <|
-            engine = Default_Engine.new
-            pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+         Text.group "should correctly evaluate documentation examples" <|
+            Test.specify "example 1" <|
+                pattern = Regex_2.compile 'aa'
+                pattern.replace 'aaa' 'b' . should_equal 'ba'
+
+            Test.specify "example 2" <|
+                pattern = Regex_2.compile '[lo]'
+                pattern.replace 'Hello World!' '#' . should_equal 'He### W#r#d!'
+
+            Test.specify "example 3" <|
+                pattern = Regex_2.compile 'l'
+                pattern.replace 'Hello World!' '#' only_first=True . should_equal 'He#lo World!'
+
+            Test.specify "example 4" <|
+                pattern = Regex_2.compile '"(.*?)"'
+                pattern.replace '"abc" foo "bar" baz' '($1)' . should_equal '(abc) foo (bar) baz'
+
+            Test.specify "example 5" <|
+                pattern = Regex_2.compile "aa"
+                input = "aa ab aa ac ad aa aa ax"
+                match = pattern.replace input "xyz"
+                match . should_equal "xyz ab xyz ac ad xyz xyz ax"
+
+            Test.specify "example 6" <|
+                pattern = Regex_2.compile "([a-z]+)"
+                pattern.replace "foo bar, baz" "[$1]" . should_equal "[foo] [bar], [baz]"
+
+        Test.specify "`replace` with an empty pattern should be an error" <|
+            pattern = Regex_2.compile ""
+            pattern.replace "ABC" . should_fail_with Illegal_Argument
+
+    Test.group "Match.text" <|
+        pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
         input = "aa ab abc a bc bcd"
-            match = pattern.match input mode=Matching_Mode.First
-            match . should_be_a Default_Engine.Match.Value
+        match = pattern.match input
+        match . should_be_a Match_2
 
         Test.specify "should return the full match with index 0" <|
-                match.group 0 . should_equal "aa ab abc a bc bcd"
+            match.text 0 . should_equal "aa ab abc a bc bcd"
 
         Test.specify "should return the group contents if it matches by index" <|
-                match.group 1 . should_equal "aa ab "
+            match.text 1 . should_equal "aa ab "
 
         Test.specify "should return the group contents if it matches by name" <|
-                match.group "letters" . should_equal "abc a bc bcd"
+            match.text "letters" . should_equal "abc a bc bcd"
 
         Test.specify "should return Nothing if the group did not match" <|
-                match.group 3 . should_equal Nothing
+            match.text 3 . should_equal Nothing
 
         Test.specify "should fail with No_Such_Group_Error if the group did not exist" <|
-                match.group "fail" . should_fail_with No_Such_Group
-                match.group 5 . should_fail_with No_Such_Group
+            match.text "fail" . should_fail_with No_Such_Group
+            match.text 5 . should_fail_with No_Such_Group
 
         Test.specify "should make named groups accessible by index" <|
-                match.group 2 . should_equal (match.group "letters")
+            match.text 2 . should_equal (match.text "letters")
 
     Test.group "Match.groups" <|
-            engine = Default_Engine.new
-            pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+        pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
         input = "aa ab abc a bc bcd"
-            match = pattern.match input mode=Matching_Mode.First
-            match . should_be_a Default_Engine.Match.Value
+        match = pattern.match input
+        match . should_be_a Match_2
 
         Test.specify "should return the results of all groups" <|
             groups = match.groups
@@ -485,59 +372,57 @@ spec =
             match.end 5 . should_fail_with No_Such_Group
             match.end "nonexistent" . should_fail_with No_Such_Group
 
-        Test.group "Match.utf16_start" <|
+    Test.group "Match.utf_16_start" <|
         pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
         input = "aa ab abc a bc bcd"
         match = pattern.match input
         match . should_be_a Match_2
 
         Test.specify "should return the start of a group by index" <|
-                match.utf16_start 1 . should_equal 0
+            match.utf_16_start 1 . should_equal 0
 
         Test.specify "should return the start of a group by name" <|
-                match.utf16_start "letters" . should_equal 6
+            match.utf_16_start "letters" . should_equal 6
 
         Test.specify "should return Nothing if the group didn't match" <|
-                match.utf16_start 3 . should_equal Nothing
-                match.utf16_start "empty" . should_equal Nothing
+            match.utf_16_start 3 . should_equal Nothing
+            match.utf_16_start "empty" . should_equal Nothing
 
         Test.specify "should return No_Such_Group_Error if the group doesn't exist" <|
-                match.utf16_start 5 . should_fail_with No_Such_Group
-                match.utf16_start "nonexistent" . should_fail_with No_Such_Group
+            match.utf_16_start 5 . should_fail_with No_Such_Group
+            match.utf_16_start "nonexistent" . should_fail_with No_Such_Group
 
-        Test.group "Match.utf16_end" <|
+        Test.group "Match.utf_16_end" <|
             pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
             input = "aa ab abc a bc bcd"
             match = pattern.match input
             match . should_be_a Match_2
 
             Test.specify "should return the end of a group by index" <|
-                match.utf16_end 1 . should_equal 6
+                match.utf_16_end 1 . should_equal 6
 
             Test.specify "should return the end of a group by name" <|
-                match.utf16_end "letters" . should_equal 18
+                match.utf_16_end "letters" . should_equal 18
 
             Test.specify "should return Nothing if the group didn't match" <|
-                match.utf16_end 3 . should_equal Nothing
-                match.utf16_end "empty" . should_equal Nothing
+                match.utf_16_end 3 . should_equal Nothing
+                match.utf_16_end "empty" . should_equal Nothing
 
             Test.specify "should return No_Such_Group_Error if the group doesn't exist" <|
-                match.utf16_end 5 . should_fail_with No_Such_Group
-                match.utf16_end "nonexistent" . should_fail_with No_Such_Group
+                match.utf_16_end 5 . should_fail_with No_Such_Group
+                match.utf_16_end "nonexistent" . should_fail_with No_Such_Group
 
-    ##
     Test.group "Match.span" <|
-            engine = Default_Engine.new
-            pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+        pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
         input = "aa ab abc a bc bcd"
-            match = pattern.match input mode=Matching_Mode.First
-            match . should_be_a Default_Engine.Match.Value
+        match = pattern.match input
+        match . should_be_a Match_2
 
         Test.specify "should get the span of a group by index" <|
-                match.span 1 . should_equal (Utf_16_Span.Value (0.up_to 6) input)
+            match.span 1 . should_equal (Span.Value (0.up_to 6) input)
 
         Test.specify "should get the span of a group by name" <|
-                match.span "letters" . should_equal (Utf_16_Span.Value (6.up_to 18) input)
+            match.span "letters" . should_equal (Span.Value (6.up_to 18) input)
 
         Test.specify "should return Nothing if the group didn't match" <|
             match.span 3 . should_equal Nothing
@@ -547,45 +432,35 @@ spec =
             match.span 5 . should_fail_with No_Such_Group
             match.span "nonexistent" . should_fail_with No_Such_Group
 
-        Test.group "Match.start_position" <|
-            engine = Default_Engine.new
-            pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
+    Test.group "Match.utf_16_span" <|
+        pattern = Regex_2.compile "(.. .. )(?<letters>.+)()??(?<empty>)??"
         input = "aa ab abc a bc bcd"
-            match = pattern.match input mode=Matching_Mode.First
-            match . should_be_a Default_Engine.Match.Value
+        match = pattern.match input
+        match . should_be_a Match_2
 
-            Test.specify "should return the region start over which self match was performed" <|
-                match.start_position . should_equal 0
+        Test.specify "should get the UTF16 span of a group by index" <|
+            match.utf_16_span 1 . should_equal (Utf_16_Span.Value (0.up_to 6) input)
 
-        Test.group "Match.end_position" <|
-            engine = Default_Engine.new
-            pattern = engine.compile "(.. .. )(?<letters>.+)()??(?<empty>)??" []
-            input = "aa ab abc a bc bcd"
-            match = pattern.match input mode=Matching_Mode.First
-            match . should_be_a Default_Engine.Match.Value
+        Test.specify "should get the UTF16 span of a group by name" <|
+            match.utf_16_span "letters" . should_equal (Utf_16_Span.Value (6.up_to 18) input)
 
-            Test.specify "should return the region end over which self match was performed" <|
-                match.end_position . should_equal 18
+        Test.specify "should return Nothing if the group didn't match" <|
+            match.utf_16_span 3 . should_equal Nothing
+            match.utf_16_span "empty" . should_equal Nothing
 
-        Test.group "Regex options handling" <|
-            Test.specify "should work properly with flag options" <|
-                flags = Regex.from_flags match_ascii=True case_insensitive=Nothing dot_matches_newline=True multiline=False comments=True extra_opts=[]
-                flags . should_equal [Regex_Option.Ascii_Matching, Regex_Option.Dot_Matches_Newline, Regex_Option.Comments]
+        Test.specify "should fail with a No_Such_Group_Error if the group doesn't exist" <|
+            match.utf_16_span 5 . should_fail_with No_Such_Group
+            match.utf_16_span "nonexistent" . should_fail_with No_Such_Group
 
-            Test.specify "should properly override vector options" <|
-                flags = Regex.from_flags match_ascii=True case_insensitive=Nothing dot_matches_newline=True multiline=False comments=True extra_opts=[Regex_Option.Multiline, Regex_Option.Case_Insensitive]
-                flags . should_equal [Regex_Option.Ascii_Matching, Regex_Option.Case_Insensitive, Regex_Option.Dot_Matches_Newline, Regex_Option.Comments]
+    Test.group "caching" <|
+        Test.specify "Replacer cache drops old values" <|
+            pattern = Regex_2.compile('([a-c])')
 
-        Test.group "Regexes" <|
-            Test.specify "should be able to be compiled" <|
-                pattern = Regex.compile "(?<dots>..)" case_insensitive=True
-                pattern . should_be_a Default_Engine.Pattern.Value
-                pattern.options . should_equal [Regex_Option.Case_Insensitive]
-
-            Test.specify "should be able to be escaped" <|
-                pattern = "http://example.com"
-                Regex.escape pattern . should_equal "\Qhttp://example.com\E"
-
-        ## TODO: Missing tests for No_Such_Group_Error
+            # Add enough values to flush out the first values.
+            0.up_to get_lru_size+1 . map i->
+                result = pattern.replace "abcdef" ("$1$1x" + i.to_text)
+                result . should_not_equal Nothing
+            replacer_cache_lookup "$1$1x0" . should_equal Nothing
+            replacer_cache_lookup "$1$1x1" . should_not_equal Nothing
 
 main = Test_Suite.run_main spec

test/Tests/src/Data/Text_Spec.enso

@@ -7,6 +7,7 @@ import Standard.Base.Errors.Common.Index_Out_Of_Bounds
 import Standard.Base.Errors.Common.Incomparable_Values
 import Standard.Base.Errors.Common.Type_Error
 import Standard.Base.Errors.Illegal_Argument.Illegal_Argument
+import Standard.Base.IO
 
 import Standard.Base.Data.Text.Regex.Engine.Default as Default_Engine
 
@@ -15,6 +16,7 @@ from Standard.Base.Data.Index_Sub_Range.Index_Sub_Range import all
 
 from Standard.Test import Test, Test_Suite
 import Standard.Test.Extensions
+import Standard.Base.Data.Text.Extensions
 
 type Auto
     Value a
@@ -1190,9 +1192,9 @@ spec =
             "Strasse".find "ß" Case_Sensitivity.Insensitive . should_equal Nothing
 
         Test.specify "find should produce correct spans" <|
-            "Hello World!".find ".o" Case_Sensitivity.Insensitive . grapheme_span 0 . should_equal (Span.Value (3.up_to 5) "Hello World!")
-            "Hello World!".find_all ".o" . map (match-> match.grapheme_span 0) . should_equal [Span.Value (3.up_to 5) "Hello World!", Span.Value (6.up_to 8) "Hello World!"]
-            "foobar".find "BAR" Case_Sensitivity.Insensitive . grapheme_span 0 . should_equal (Span.Value (3.up_to 6) "foobar")
+            "Hello World!".find ".o" Case_Sensitivity.Insensitive . span 0 . should_equal (Span.Value (3.up_to 5) "Hello World!")
+            "Hello World!".find_all ".o" . map (match-> match.span 0) . should_equal [Span.Value (3.up_to 5) "Hello World!", Span.Value (6.up_to 8) "Hello World!"]
+            "foobar".find "BAR" Case_Sensitivity.Insensitive . span 0 . should_equal (Span.Value (3.up_to 6) "foobar")
 
         Test.specify "should handle accents and other multi-point graphemes" <|
             accents = 'a\u{301}e\u{301}o\u{301}he\u{301}h'
@@ -1201,29 +1203,20 @@ spec =
             accents.find 'e\u{301}' . text 0 . should_equal 'e\u{301}'
 
             # Check both UTF16 spans
-            accents.find_all 'h' . map (match-> match.span 0) . should_equal [Utf_16_Span.Value (6.up_to 7) accents, Utf_16_Span.Value (9.up_to 10) accents]
-            accents.find_all 'e\u{301}' . map (match-> match.span 0) . should_equal [Utf_16_Span.Value (2.up_to 4) accents, Utf_16_Span.Value (7.up_to 9) accents]
+            accents.find_all 'h' . map (match-> match.utf_16_span 0) . should_equal [Utf_16_Span.Value (6.up_to 7) accents, Utf_16_Span.Value (9.up_to 10) accents]
+            accents.find_all 'e\u{301}' . map (match-> match.utf_16_span 0) . should_equal [Utf_16_Span.Value (2.up_to 4) accents, Utf_16_Span.Value (7.up_to 9) accents]
 
             # Check both grapheme spans
-            accents.find_all 'h' . map (match-> match.grapheme_span 0) . should_equal [Span.Value (3.up_to 4) accents, Span.Value (5.up_to 6) accents]
-            accents.find_all 'e\u{301}' . map (match-> match.grapheme_span 0) . should_equal [Span.Value (1.up_to 2) accents, Span.Value (4.up_to 5) accents]
+            accents.find_all 'h' . map (match-> match.span 0) . should_equal [Span.Value (3.up_to 4) accents, Span.Value (5.up_to 6) accents]
+            accents.find_all 'e\u{301}' . map (match-> match.span 0) . should_equal [Span.Value (1.up_to 2) accents, Span.Value (4.up_to 5) accents]
 
             # Check contents to make sure the spans' ranges are ok
             accents.find 'h' . text 0 . should_equal 'h'
             accents.find 'e\u{301}' . text 0 . should_equal 'e\u{301}'
 
-        Test.specify "should correctly handle regex edge cases in locate" pending="Figure out how to make Regex correctly handle empty patterns." <|
-            regex = Regex_Matcher.Value
-            "".match "foo" matcher=regex . should_equal Nothing
-            "".match "foo" matcher=regex mode=Matching_Mode.Last . should_equal Nothing
-            "".match_all "foo" matcher=regex . should_equal []
-            "".match "" matcher=regex . should_equal ""
-            "".match_all "" matcher=regex . should_equal [""]
-            "".match "" matcher=regex mode=Matching_Mode.Last . should_equal ""
-            abc = 'A\u{301}ßC'
-            abc.match "" matcher=regex . should_equal abc
-            abc.match_all "" matcher=regex . should_equal ["", "", "", "", ""]
-            abc.match "" matcher=regex mode=Matching_Mode.Last . should_equal ""
+        Test.specify "should correctly handle regex edge cases in `find`" <|
+            "".find "foo" . should_equal Nothing
+            "".find_all "foo" . should_equal []
 
         Test.specify "should handle overlapping matches as shown in the examples" <|
             "aaa".locate "aa" mode=Matching_Mode.Last case_sensitivity=Case_Sensitivity.Sensitive . should_equal (Span.Value (1.up_to 3) "aaa")
@@ -1256,6 +1249,12 @@ spec =
             txt.find "^m..a..z.a$" . text 0 . should_equal "maza건반zaa"
             txt.find "a..z" . text 0 . should_equal "a건반z"
 
+        Test.specify "`find` with an empty pattern should be an error" <|
+            'b'.find '' . should_fail_with Illegal_Argument
+
+        Test.specify "`find_all` with an empty pattern should be an error" <|
+            'b'.find_all '' . should_fail_with Illegal_Argument
+
         Test.specify "should be possible in case-insensitive mode" <|
             "MY".find "my" Case_Sensitivity.Insensitive . text 0 . should_equal "MY"
 
@@ -1281,20 +1280,20 @@ spec =
                expose normalization methods to allow developers to do it
                themselves.
             accents = 'a\u{301}e\u{301}o\u{301}'
-            accents.find accent_1 . grapheme_span 0 . should_equal (Span.Value (1.up_to 2) 'a\u{301}e\u{301}o\u{301}')
+            accents.find accent_1 . span 0 . should_equal (Span.Value (1.up_to 2) 'a\u{301}e\u{301}o\u{301}')
 
         Test.specify "can return a vector of all match groups" <|
             "abc".find "ab((c)|(d))" . groups . should_equal ['abc', 'c', 'c', Nothing]
 
-        Test.specify "should default to group 0 in .span and .grapheme_span" <|
-            "abacadae".find "a[bc]" . span . should_equal (Utf_16_Span.Value (0.up_to 2) "abacadae")
-            'a\u{301}e\u{301}o\u{301}'.find 'e\u{301}' . grapheme_span . should_equal (Span.Value (1.up_to 2) 'a\u{301}e\u{301}o\u{301}')
+        Test.specify "should default to group 0 in .span and .span" <|
+            "abacadae".find "a[bc]" . utf_16_span . should_equal (Utf_16_Span.Value (0.up_to 2) "abacadae")
+            'a\u{301}e\u{301}o\u{301}'.find 'e\u{301}' . span . should_equal (Span.Value (1.up_to 2) 'a\u{301}e\u{301}o\u{301}')
 
         Test.specify "should allow to match one or more occurrences of a pattern in the text" <|
-            "abacadae".find_all "a[bc]" . map (match-> match.grapheme_span 0) . should_equal [Span.Value (0.up_to 2) "abacadae", Span.Value (2.up_to 4) "abacadae"]
-            "abacadae".find_all "a." . map (match-> match.grapheme_span 0) . should_equal [Span.Value (0.up_to 2) "abacadae", Span.Value (2.up_to 4) "abacadae", Span.Value (4.up_to 6) "abacadae", Span.Value (6.up_to 8) "abacadae"]
-            "abacadae".find_all "a.*" . map (match-> match.grapheme_span 0) . should_equal [Span.Value (0.up_to 8) "abacadae"]
-            "abacadae".find_all "a.+?" . map (match-> match.grapheme_span 0) . should_equal [Span.Value (0.up_to 2) "abacadae", Span.Value (2.up_to 4) "abacadae", Span.Value (4.up_to 6) "abacadae", Span.Value (6.up_to 8) "abacadae"]
+            "abacadae".find_all "a[bc]" . map (match-> match.span 0) . should_equal [Span.Value (0.up_to 2) "abacadae", Span.Value (2.up_to 4) "abacadae"]
+            "abacadae".find_all "a." . map (match-> match.span 0) . should_equal [Span.Value (0.up_to 2) "abacadae", Span.Value (2.up_to 4) "abacadae", Span.Value (4.up_to 6) "abacadae", Span.Value (6.up_to 8) "abacadae"]
+            "abacadae".find_all "a.*" . map (match-> match.span 0) . should_equal [Span.Value (0.up_to 8) "abacadae"]
+            "abacadae".find_all "a.+?" . map (match-> match.span 0) . should_equal [Span.Value (0.up_to 2) "abacadae", Span.Value (2.up_to 4) "abacadae", Span.Value (4.up_to 6) "abacadae", Span.Value (6.up_to 8) "abacadae"]
 
         Test.specify "should allow access to match groups by number" <|
             "abcddd".find "ab(c(d+))" . text 0 . should_equal "abcddd"
@@ -1331,8 +1330,13 @@ spec =
         Test.specify "should expand a partial-grapheme match to the whole grapheme" <|
             'e\u{301}'.find '\u{301}' . text 0 . should_equal 'e\u{301}'
 
+        Test.specify "should not allow non-default locale" <|
+            locale = Locale.new "en" "GB" "UTF-8"
+            'a'.find 'a' case_sensitivity=(Case_Sensitivity.Insensitive locale) . should_fail_with Illegal_Argument
+            'a'.find_all 'a' case_sensitivity=(Case_Sensitivity.Insensitive locale) . should_fail_with Illegal_Argument
+
     Test.group "Text.match" <|
-        Test.specify "should default to regex" <|
+        Test.specify "should work correctly" <|
             "My Text: Goes Here".match "^My Text: (.+)$" . should_be_true
             "555-801-1923".match "^\d{3}-\d{3}-\d{4}$" . should_be_true
             "Hello".match "^[a-z]+$" . should_be_false
@@ -1344,12 +1348,19 @@ spec =
             "abcd".match "abc" . should_be_false
             "x".match "[a-z]" . should_be_true
 
+        Test.specify "`match` with an empty pattern should be an error" <|
+                'b'.match '' . should_fail_with Illegal_Argument
+
         Test.specify "should be possible on unicode text" <|
             "Korean: 건반".match "^Korean: (.+)$" . should_be_true
 
         Test.specify "should be possible in case-insensitive mode" <|
             "MY".match "my" Case_Sensitivity.Insensitive . should_be_true
 
+        Test.specify "should not allow non-default locale" <|
+            locale = Locale.new "en" "GB" "UTF-8"
+            'a'.match 'a' case_sensitivity=(Case_Sensitivity.Insensitive locale) . should_fail_with Illegal_Argument
+
     Test.group "Regex splitting" <|
         Test.specify "should be possible on text" <|
             splits = "abcde".split "[bd]" Regex_Matcher.Value
@@ -1402,141 +1413,113 @@ spec =
     Test.group "Text.replace" <|
         Test.specify "should work as in examples" <|
             'aaa'.replace 'aa' 'b' . should_equal 'ba'
-            "Hello World!".replace "[lo]" "#" matcher=Regex_Matcher.Value . should_equal "He### W#r#d!"
-            "Hello World!".replace "l" "#" mode=Matching_Mode.First . should_equal "He#lo World!"
-            '"abc" foo "bar" baz'.replace '"(.*?)"' '($1)' matcher=Regex_Matcher.Value . should_equal '(abc) foo (bar) baz'
-            'ß'.replace 'S' 'A' matcher=Text_Matcher.Case_Insensitive . should_equal 'AA'
-            'affib'.replace 'i' 'X' matcher=Text_Matcher.Case_Insensitive . should_equal 'aXb'
+            "Hello World!".replace "[lo]" "#" use_regex=True . should_equal "He### W#r#d!"
+            "Hello World!".replace "l" "#" only_first=True . should_equal "He#lo World!"
+            '"abc" foo "bar" baz'.replace '"(.*?)"' '($1)' use_regex=True . should_equal '(abc) foo (bar) baz'
+
+        Test.specify "works when mapped over a vector of inputs" <|
+            inputs = ["axyz", "bxyz", "xabcz", "zazaz"]
+            inputs.map (s-> s.replace "[abc]" "q" use_regex=True) . should_equal ["qxyz", "qxyz", "xqqqz", "zqzqz"]
 
         Test.specify "should correctly handle empty-string edge cases" <|
-            [Regex_Mode.All, Matching_Mode.First, Matching_Mode.Last] . each mode->
-                'aaa'.replace '' 'foo' mode=mode . should_equal 'aaa'
-                ''.replace '' '' mode=mode . should_equal ''
-                'a'.replace 'a' '' mode=mode . should_equal ''
-                ''.replace 'a' 'b' mode=mode . should_equal ''
+            [True, False] . each only_first->
+                'aaa'.replace '' 'foo' only_first=only_first . should_equal 'aaa'
+                'a'.replace 'a' '' only_first=only_first . should_equal ''
+                ''.replace 'a' 'b' only_first=only_first . should_equal ''
 
-            'aba' . replace 'a' '' Matching_Mode.First . should_equal 'ba'
-            'aba' . replace 'a' '' Matching_Mode.Last . should_equal 'ab'
+            'aba' . replace 'a' '' only_first=True . should_equal 'ba'
             'aba' . replace 'a' '' . should_equal 'b'
             'aba' . replace 'c' '' . should_equal 'aba'
 
         Test.specify "should correctly handle first, all and last matching with overlapping occurrences" <|
             "aaa aaa".replace "aa" "c" . should_equal "ca ca"
-            "aaa aaa".replace "aa" "c" mode=Matching_Mode.First . should_equal "ca aaa"
-            "aaa aaa".replace "aa" "c" mode=Matching_Mode.Last . should_equal "aaa ac"
+            "aaa aaa".replace "aa" "c" only_first=True . should_equal "ca aaa"
+
+        Test.specify "Regex `replace` with an empty pattern should be an error" <|
+                'b'.replace '' 'c' use_regex=True . should_fail_with Illegal_Argument
 
         Test.specify "should correctly handle case-insensitive matches" <|
-            'AaąĄ' . replace "A" "-" matcher=Text_Matcher.Case_Insensitive . should_equal '--ąĄ'
+            'AaąĄ' . replace "A" "-" case_sensitivity=Case_Sensitivity.Insensitive . should_equal '--ąĄ'
             'AaąĄ' . replace "A" "-" . should_equal '-aąĄ'
-            'HeLlO wOrLd' . replace 'hElLo' 'Hey,' matcher=Text_Matcher.Case_Sensitive . should_equal 'HeLlO wOrLd'
-            'HeLlO wOrLd' . replace 'hElLo' 'Hey,' matcher=Text_Matcher.Case_Insensitive . should_equal 'Hey, wOrLd'
+            'HeLlO wOrLd' . replace 'hElLo' 'Hey,' case_sensitivity=Case_Sensitivity.Sensitive . should_equal 'HeLlO wOrLd'
+            'HeLlO wOrLd' . replace 'hElLo' 'Hey,' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'Hey, wOrLd'
 
             "Iiİı" . replace "i" "-" . should_equal "I-İı"
             "Iiİı" . replace "I" "-" . should_equal "-iİı"
             "Iiİı" . replace "İ" "-" . should_equal "Ii-ı"
             "Iiİı" . replace "ı" "-" . should_equal "Iiİ-"
 
-            "Iiİı" . replace "i" "-" matcher=Text_Matcher.Case_Insensitive . should_equal "--İı"
-            "Iiİı" . replace "I" "-" matcher=Text_Matcher.Case_Insensitive . should_equal "--İı"
-            "Iiİı" . replace "İ" "-" matcher=Text_Matcher.Case_Insensitive . should_equal "Ii-ı"
-            "Iiİı" . replace "ı" "-" matcher=Text_Matcher.Case_Insensitive . should_equal "Iiİ-"
+            "Iiİı" . replace "i" "-" case_sensitivity=Case_Sensitivity.Insensitive . should_equal "--İı"
+            "Iiİı" . replace "I" "-" case_sensitivity=Case_Sensitivity.Insensitive . should_equal "--İı"
+            "Iiİı" . replace "İ" "-" case_sensitivity=Case_Sensitivity.Insensitive . should_equal "Ii-ı"
+            "Iiİı" . replace "ı" "-" case_sensitivity=Case_Sensitivity.Insensitive . should_equal "Iiİ-"
 
-            tr_insensitive = Text_Matcher.Case_Insensitive (Locale.new "tr")
-            "Iiİı" . replace "i" "-" matcher=tr_insensitive . should_equal "I--ı"
-            "Iiİı" . replace "I" "-" matcher=tr_insensitive . should_equal "-iİ-"
-            "Iiİı" . replace "İ" "-" matcher=tr_insensitive . should_equal "I--ı"
-            "Iiİı" . replace "ı" "-" matcher=tr_insensitive . should_equal "-iİ-"
+        Test.specify "should correctly handle Unicode" <|
+            'ß'.replace 'S' 'A' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'AA'
+            'ß'.replace 'ß' 'A' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'A'
+            'affib'.replace 'i' 'X' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'aXb'
+            'affib'.replace 'ffi' 'X' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'aXb'
 
-        Test.specify "should correctly handle Unicode edge cases" <|
             'sśs\u{301}' . replace 's' 'O' . should_equal 'Ośs\u{301}'
-            'sśs\u{301}' . replace 's' 'O' Matching_Mode.Last . should_equal 'Ośs\u{301}'
-            'śs\u{301}s' . replace 's' 'O' Matching_Mode.First . should_equal 'śs\u{301}O'
+            'śss\u{301}' . replace 's' 'O' only_first=True . should_equal 'śOs\u{301}'
 
             'sśs\u{301}' . replace 'ś' 'O' . should_equal 'sOO'
+            'śss\u{301}' . replace 'ś' 'O' only_first=True . should_equal 'Oss\u{301}'
+
             'sśs\u{301}' . replace 's\u{301}' 'O' . should_equal 'sOO'
+            's\u{301}śs' . replace 's\u{301}' 'O' . should_equal 'OOs'
 
             'SŚS\u{301}' . replace 's' 'O' . should_equal 'SŚS\u{301}'
-            'SŚS\u{301}' . replace 's' 'O' Matching_Mode.Last . should_equal 'SŚS\u{301}'
-            'ŚS\u{301}S' . replace 's' 'O' Matching_Mode.First . should_equal 'ŚS\u{301}S'
+            'ŚS\u{301}S' . replace 's' 'O' only_first=True . should_equal 'ŚS\u{301}S'
 
             'SŚS\u{301}' . replace 'ś' 'O' . should_equal 'SŚS\u{301}'
             'SŚS\u{301}' . replace 's\u{301}' 'O' . should_equal 'SŚS\u{301}'
 
-            'SŚS\u{301}' . replace 's' 'O' matcher=Text_Matcher.Case_Insensitive . should_equal 'OŚS\u{301}'
-            'SŚS\u{301}' . replace 's' 'O' Matching_Mode.Last matcher=Text_Matcher.Case_Insensitive . should_equal 'OŚS\u{301}'
-            'ŚS\u{301}S' . replace 's' 'O' Matching_Mode.First matcher=Text_Matcher.Case_Insensitive . should_equal 'ŚS\u{301}O'
+            'SŚS\u{301}' . replace 's' 'O' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'OŚS\u{301}'
+            'ŚS\u{301}S' . replace 's' 'O' only_first=True case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'ŚS\u{301}O' # 'ŚO\u{301}O' # 'ŚOS\u{301}S'
 
-            'SŚS\u{301}' . replace 'ś' 'O' matcher=Text_Matcher.Case_Insensitive . should_equal 'SOO'
-            'SŚS\u{301}' . replace 's\u{301}' 'O' matcher=Text_Matcher.Case_Insensitive . should_equal 'SOO'
+            'SŚS\u{301}' . replace 'ś' 'O' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'SOO'
+            'SŚS\u{301}' . replace 's\u{301}' 'O' case_sensitivity=Case_Sensitivity.Insensitive . should_equal 'SOO'
 
             '✨🚀🚧😍😃😍😎😙😉☺' . replace '🚧😍' '|-|:)' . should_equal '✨🚀|-|:)😃😍😎😙😉☺'
             'Rocket Science' . replace 'Rocket' '🚀' . should_equal '🚀 Science'
 
             "Korean: 건반".replace "건반" "keyboard" . should_equal "Korean: keyboard"
 
-        Test.specify "will approximate ligature matches" <|
-            # TODO do we want to improve this? highly non-trivial for very rare edge cases
-            ## Currently we lack 'resolution' to extract a partial match from
-               the ligature to keep it, probably would need some special
-               mapping.
-            'ffiffi'.replace 'ff' 'aa' matcher=Text_Matcher.Case_Insensitive . should_equal 'aaaa'
-            'ffiffi'.replace 'ff' 'aa' mode=Matching_Mode.First matcher=Text_Matcher.Case_Insensitive . should_equal 'aaffi'
-            'ffiffi'.replace 'ff' 'aa' mode=Matching_Mode.Last matcher=Text_Matcher.Case_Insensitive . should_equal 'ffiaa'
-            'affiffib'.replace 'IF' 'X' matcher=Text_Matcher.Case_Insensitive . should_equal 'aXb'
-            'aiffiffz' . replace 'if' '-' matcher=Text_Matcher.Case_Insensitive . should_equal 'a--fz'
-            'AFFIB'.replace 'ffi' '-' matcher=Text_Matcher.Case_Insensitive . should_equal 'A-B'
-
-            'ß'.replace 'SS' 'A' matcher=Text_Matcher.Case_Insensitive . should_equal 'A'
-            'ß'.replace 'S' 'A' matcher=Text_Matcher.Case_Insensitive . should_equal 'AA'
-            'ß'.replace 'S' 'A' mode=Matching_Mode.First matcher=Text_Matcher.Case_Insensitive . should_equal 'A'
-            'ß'.replace 'S' 'A' mode=Matching_Mode.Last matcher=Text_Matcher.Case_Insensitive . should_equal 'A'
-            'STRASSE'.replace 'ß' '-' matcher=Text_Matcher.Case_Insensitive . should_equal 'STRA-E'
+        Test.specify "regex and non-regex replace handle accented grapheme splitting differently" <|
+            'sśs\u{301}' . replace 's' 'O' . should_equal 'Ośs\u{301}'
+            'sśs\u{301}' . replace 's' 'O' use_regex=True . should_equal 'OśO\u{301}'
 
         Test.specify "should perform simple replacement in Regex mode" <|
-            "ababab".replace "b" "a" matcher=Regex_Matcher.Value . should_equal "aaaaaa"
-            "ababab".replace "b" "a" mode=Matching_Mode.First matcher=Regex_Matcher.Value . should_equal "aaabab"
-            "ababab".replace "b" "a" mode=Matching_Mode.Last matcher=Regex_Matcher.Value . should_equal "ababaa"
+            "ababab".replace "b" "a" use_regex=True . should_equal "aaaaaa"
+            "ababab".replace "b" "a" only_first=True use_regex=True . should_equal "aaabab"
 
-            "aaaa".replace "aa" "c" matcher=Regex_Matcher.Value . should_equal "cc"
-            "aaaa".replace "aa" "c" mode=Matching_Mode.First matcher=Regex_Matcher.Value . should_equal "caa"
-            "aaaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Regex_Matcher.Value . should_equal "aac"
+            "aaaa".replace "aa" "c" use_regex=True . should_equal "cc"
+            "aaaa".replace "aa" "c" only_first=True use_regex=True . should_equal "caa"
 
-            "aaa".replace "aa" "c" matcher=Regex_Matcher.Value . should_equal "ca"
-            "aaa".replace "aa" "c" mode=Matching_Mode.First matcher=Regex_Matcher.Value . should_equal "ca"
-            "aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Text_Matcher.Case_Sensitive . should_equal "ac"
-            "aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Regex_Matcher.Value . should_equal "ca"
+            "aaa".replace "aa" "c" use_regex=True . should_equal "ca"
+            "aaa".replace "aa" "c" only_first=True use_regex=True . should_equal "ca"
 
-            "aaa aaa".replace "aa" "c" matcher=Text_Matcher.Case_Sensitive . should_equal "ca ca"
-            "aaa aaa".replace "aa" "c" mode=Matching_Mode.First matcher=Text_Matcher.Case_Sensitive . should_equal "ca aaa"
-            "aaa aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Text_Matcher.Case_Sensitive . should_equal "aaa ac"
-            "aaa aaa".replace "aa" "c" matcher=Regex_Matcher.Value . should_equal "ca ca"
-            "aaa aaa".replace "aa" "c" mode=Matching_Mode.First matcher=Regex_Matcher.Value . should_equal "ca aaa"
-            "aaa aaa".replace "aa" "c" mode=Matching_Mode.Last matcher=Regex_Matcher.Value . should_equal "aaa ca"
+            "aaa aaa".replace "aa" "c" case_sensitivity=Case_Sensitivity.Sensitive use_regex=True . should_equal "ca ca"
+            "aaa aaa".replace "aa" "c" only_first=True case_sensitivity=Case_Sensitivity.Sensitive use_regex=True . should_equal "ca aaa"
+            "aaa aaa".replace "aa" "c" use_regex=True . should_equal "ca ca"
+            "aaa aaa".replace "aa" "c" only_first=True use_regex=True . should_equal "ca aaa"
 
         Test.specify "in Regex mode should work with Unicode" <|
-            "Korean: 건반".replace "건반" "keyboard" matcher=Regex_Matcher.Value . should_equal "Korean: keyboard"
-            'sśs\u{301}'.replace 'ś' '-' matcher=Regex_Matcher.Value . should_equal 's--'
-            'sśs\u{301}'.replace 's\u{301}' '-' matcher=Regex_Matcher.Value . should_equal 's--'
-
-        Test.specify "in Regex mode should support various Regex options" <|
-            r1 = "İiİ".replace "\w" "a" matcher=(Regex_Matcher.Value match_ascii=True)
-            r1 . should_equal "İaİ"
-            r2 = "abaBa".replace "b" "a" matcher=(Regex_Matcher.Value case_sensitivity=Case_Sensitivity.Insensitive)
-            r2 . should_equal "aaaaa"
-            r3 = 'ab\na'.replace "b." "a"  matcher=(Regex_Matcher.Value dot_matches_newline=True)
-            r3 . should_equal "aaa"
-
-            text = """
-                Foo
-                bar
-            r4 = text.replace '\n' ""  matcher=(Regex_Matcher.Value multiline=True)
-            r4 . should_equal "Foobar"
-
-            r5 = "ababd".replace "b\w # Replacing a `b` followed by any word character" "a" matcher=(Regex_Matcher.Value comments=True)
-            r5 . should_equal "aaa"
+            "Korean: 건반".replace "건반" "keyboard" use_regex=True . should_equal "Korean: keyboard"
+            'sśs\u{301}'.replace 'ś' '-' use_regex=True . should_equal 's-s\u{301}'
+            'sśs\u{301}'.replace 's\u{301}' '-' use_regex=True . should_equal 'sś-'
 
         Test.specify "in Regex mode should allow referring to capture groups in substitutions" <|
-            '<a href="url">content</a>'.replace '<a href="(.*?)">(.*?)</a>' '$2 is at $1' matcher=Regex_Matcher.Value . should_equal 'content is at url'
-            '<a href="url">content</a>'.replace '<a href="(?<address>.*?)">(?<text>.*?)</a>' '${text} is at ${address}' matcher=Regex_Matcher.Value . should_equal 'content is at url'
+            '<a href="url">content</a>'.replace '<a href="(.*?)">(.*?)</a>' '$2 is at $1' use_regex=True . should_equal 'content is at url'
+            '<a href="url">content</a>'.replace '<a href="(?<address>.*?)">(?<text>.*?)</a>' '$<text> is at $<address>' use_regex=True . should_equal 'content is at url'
+
+        Test.specify "should not allow non-default locale in regex replace" <|
+            locale = Locale.new "en" "GB" "UTF-8"
+            'a'.replace 'a' 'b' case_sensitivity=(Case_Sensitivity.Insensitive locale) use_regex=True . should_fail_with Illegal_Argument
+
+        Test.specify "should allow non-default locale in text replace" <|
+            locale = Locale.new "en" "GB" "UTF-8"
+            'a'.replace 'a' 'b' case_sensitivity=(Case_Sensitivity.Insensitive locale) . should_equal 'b'
 
 main = Test_Suite.run_main spec