megaparsec/CHANGELOG.md

Megaparsec 4.4.0

• Now state returned on failure is the exact state of parser at the moment when it failed, which makes incremental parsing feature much better and opens possibilities for features like “on-the-fly” recovering from parse errors.

• The count combinator now works with Applicative instances (previously it worked only with instances of Alternative). It's now also faster.

• tokens and parsers built upon it (such as string and string') backtrack automatically on failure now, that is, when they fail, they never consume any input. This is done to make their consumption model match how error messages are reported (which becomes an important thing as user gets more control with primitives like withRecovery). This means, in particular, that it's no longer necessary to use try with tokens-based parsers. This new feature does not affect performance in any way.

• New primitive parser withRecovery added. The parser allows to recover from parse errors “on-the-fly” and continue parsing. Once parsing is finished, several parse errors may be reported or ignored altogether.

• eitherP combinator added.

• Removed Enum instance of Message type. This was Parsec's legacy that we should eliminate now. Message does not constitute enumeration, toEnum was never properly defined for it. The idea to use fromEnum to determine type of Message is also ugly, for this purpose new functions isUnexpected, isExpected, and isMessage are defined in Text.Megaparsec.Error.

• Minor tweak in signature of MonadParsec type class. Collection of constraints changed from Alternative m, Monad m, Stream s t to Alternative m, MonadPlus m, Stream s t. This is done to make it easier to write more abstract code with older GHC where such primitives as guard are defined for instances of MonadPlus, not Alternative.

Megaparsec 4.3.0

• Canonicalized Applicative/Monad instances. Thanks to Herbert Valerio Riedel.

• Custom messages in ParseError are printed each on its own line.

• Now accumulated hints are not used with ParseError records that have only custom messages in them (created with Message constructor, as opposed to Unexpected or Expected). This strips “expected” line from custom error messages where it's unlikely to be relevant anyway.

• Added higher-level combinators for indentation-sensitive grammars: indentLevel, nonIndented, and indentBlock.

Megaparsec 4.2.0

• Made newPos constructor and other functions in Text.Megaparsec.Pos smarter. Now it's impossible to create SourcePos with non-positive line number or column number. Unfortunately we cannot use Numeric.Natural because we need to support older versions of base.

• ParseError is now a monoid. mergeError is used as mappend.

• Added functions addErrorMessages and newErrorMessages to add several messages to existing error and to construct error with several attached messages respectively.

• parseFromFile now lives in Text.Megaparsec.Prim. Previously we had 5 nearly identical definitions of the function, varying only in type-specific readFile function. Now the problem is solved by introduction of StorableStream type class. All supported stream types are instances of the class out of box and thus we have polymorphic version of parseFromFile.

• ParseError is now instance of Exception (and Typeable).

• Introduced runParser' and runParserT' functions that take and return parser state. This makes it possible to partially parse input, resume parsing, specify non-standard initial textual position, etc.

• Introduced failure function that allows to fail with arbitrary collection of messages. unexpected is now defined in terms of failure. One consequence of this design decision is that failure is now method of MonadParsec, while unexpected is not.

• Removed deprecated combinators from Text.Megaparsec.Combinator:

  • chainl
  • chainl1
  • chainr
  • chainr1

• number parser in Text.Megaparsec.Lexer now can be used with signed combinator to parse either signed Integer or signed Double.

Megaparsec 4.1.1

• Fixed bug in implementation of sepEndBy and sepEndBy1 and removed deprecation notes for these functions.

• Added tests for sepEndBy and sepEndBy1.

Megaparsec 4.1.0

• Relaxed dependency on base, so that minimal required version of base is now 4.6.0.0. This allows Megaparsec to compile with GHC 7.6.x.

• Text.Megaparsec and Text.Megaparsec.Prim do not export data types Consumed and Reply anymore because they are rather low-level implementation details that should not be visible to end-user.

• Representation of file name and textual position in error messages was made conventional.

• Fixed some typos is documentation and other materials.

Megaparsec 4.0.0

General changes

• Renamed many1 → some as well as other parsers that had many1 part in their names.

• The following functions are now re-exported from Control.Applicative: (<|>), many, some, optional. See #9.

• Introduced type class MonadParsec in the style of MTL monad transformers. Eliminated built-in user state since it was not flexible enough and can be emulated via stack of monads. Now all tools in Megaparsec work with any instance of MonadParsec, not only with ParsecT.

• Added new function parseMaybe for lightweight parsing where error messages (and thus file name) are not important and entire input should be parsed. For example it can be used when parsing of single number according to specification of its format is desired.

• Fixed bug with notFollowedBy always succeeded with parsers that don't consume input, see #6.

• Flipped order of arguments in the primitive combinator label, see #21.

• Renamed tokenPrim → token, removed old token, because tokenPrim is more general and original token is little used.

• Made token parser more powerful, now its second argument can return Either [Message] a instead of Maybe a, so it can influence error message when parsing of token fails. See #29.

• Added new primitive combinator hidden p which hides “expected” tokens in error message when parser p fails.

• Tab width is not hard-coded anymore. It can be manipulated via getTabWidth and setTabWidth. Default tab-width is defaultTabWidth, which is 8.

Error messages

• Introduced type class ShowToken and improved representation of characters and strings in error messages, see #12.

• Greatly improved quality of error messages. Fixed entire Text.Megaparsec.Error module, see #14 for more information. Made possible normal analysis of error messages without “render and re-parse” approach that previous maintainers had to practice to write even simplest tests, see module Utils.hs in old-tests for example.

• Reduced number of Message constructors (now there are only Unexpected, Expected, and Message). Empty “magic” message strings are ignored now, all the library now uses explicit error messages.

• Introduced hint system that greatly improves quality of error messages and made code of Text.Megaparsec.Prim a lot clearer.

Built-in combinators

• All built-in combinators in Text.Megaparsec.Combinator now work with any instance of Alternative (some of them even with Applicaitve).

• Added more powerful count' parser. This parser can be told to parse from m to n occurrences of some thing. count is defined in terms of count'.

• Removed optionMaybe parser, because optional from Control.Applicative does the same thing.

• Added combinator someTill.

• These combinators are considered deprecated and will be removed in future:

  • chainl
  • chainl1
  • chainr
  • chainr1
  • sepEndBy
  • sepEndBy1

Character parsing

• Renamed some parsers:

  • alphaNum → alphaNumChar
  • digit → digitChar
  • endOfLine → eol
  • hexDigit → hexDigitChar
  • letter → letterChar
  • lower → lowerChar
  • octDigit → octDigitChar
  • space → spaceChar
  • spaces → space
  • upper → upperChar

• Added new character parsers in Text.Megaparsec.Char:

  • asciiChar
  • charCategory
  • controlChar
  • latin1Char
  • markChar
  • numberChar
  • printChar
  • punctuationChar
  • separatorChar
  • symbolChar

• Descriptions of old parsers have been updated to accent some Unicode-specific moments. For example, old description of letter stated that it parses letters from “a” to “z” and from “A” to “Z”. This is wrong, since it used Data.Char.isAlpha predicate internally and thus parsed many more characters (letters of non-Latin languages, for example).

• Added combinators char', oneOf', noneOf', and string' which are case-insensitive variants of char, oneOf, noneOf, and string respectively.

Lexer

• Rewritten parsing of numbers, fixed #2 and #3 (in old Parsec project these are number 35 and 39 respectively), added per bug tests.

  • Since Haskell report doesn't say anything about sign, integer and float now parse numbers without sign.

  • Removed natural parser, it's equal to new integer now.

  • Renamed naturalOrFloat → number — this doesn't parse sign too.

  • Added new combinator signed to parse all sorts of signed numbers.

• Transformed Text.Parsec.Token into Text.Megaparsec.Lexer. Little of Parsec's code remains in the new lexer module. New module doesn't impose any assumptions on user and should be vastly more useful and general. Hairy stuff from original Parsec didn't get here, for example built-in Haskell functions are used to parse escape sequences and the like instead of trying to re-implement the whole thing.

Other

• Renamed the following functions:

  • permute → makePermParser
  • buildExpressionParser → makeExprParser

• Added comprehensive QuickCheck test suite.

• Added benchmarks.

Parsec 3.1.9

• Many and various updates to documentation and package description (including the homepage links).

• Add an Eq instance for ParseError.

• Fixed a regression from 3.1.6: runP is again exported from module Text.Parsec.

Parsec 3.1.8

• Fix a regression from 3.1.6 related to exports from the main module.

Parsec 3.1.7

• Fix a regression from 3.1.6 related to the reported position of error messages. See bug #9 for details.

• Reset the current error position on success of lookAhead.

Parsec 3.1.6

• Export Text instances from Text.Parsec.

• Make Text.Parsec exports more visible.

• Re-arrange Text.Parsec exports.

• Add functions crlf and endOfLine to Text.Parsec.Char for handling input streams that do not have normalized line terminators.

• Fix off-by-one error in Token.charControl.

Parsec 3.1.4 & 3.1.5

• Bump dependency on text.

Parsec 3.1.3

• Fix a regression introduced in 3.1.2 related to positions reported by error messages.