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@ -30,7 +30,7 @@ double paragraphs, and single notes.
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# In Perl 6, you declare a lexical variable using `my`
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my $variable;
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# Perl 6 has 4 variable types :
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# Perl 6 has 4 kinds of variables:
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## * Scalars. They represent a single value. They start with a `$`
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@ -56,7 +56,8 @@ my @array = <a b c>; # array of words, delimited by space.
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say @array[2]; # Array indices start at 0 -- This is the third element
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say "Interpolate an array using [] : @array[]"; #=> Interpolate an array using [] : a b c
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say "Interpolate an array using [] : @array[]";
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#=> Interpolate an array using [] : a b c
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## * Hashes. Key-Value Pairs.
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# Hashes are actually arrays of Pairs (`Key => Value`),
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@ -99,7 +100,7 @@ my &s = &say-hello;
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my &other-s = sub { say "Anonymous function !" }
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# A sub can have a "slurpy" parameter, or "doesn't-matter-how-many"
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sub as-many($head, *@rest) { # The `*@` slurpy will basically "take everything else".
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sub as-many($head, *@rest) { # `*@` (slurpy) will basically "take everything else".
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# Note: you can have parameters *before* (like here)
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# a slurpy one, but not *after*.
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say @rest.join(' / ') ~ " !";
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@ -191,7 +192,7 @@ named-def(def => 15); #=> 15
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# its right. When passed around, containers are marked as immutable.
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# Which means that, in a function, you'll get an error if you try to
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# mutate one of your arguments.
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# If you really need to, you can ask for a mutable container using `is rw` :
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# If you really need to, you can ask for a mutable container using `is rw`:
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sub mutate($n is rw) {
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$n++;
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say "\$n is now $n !";
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@ -199,7 +200,7 @@ sub mutate($n is rw) {
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# If what you want is a copy instead, use `is copy`.
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# A sub itself returns a container, which means it can be marked as rw :
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# A sub itself returns a container, which means it can be marked as rw:
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my $x = 42;
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sub mod() is rw { $x }
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mod() = 52; # in this case, the parentheses are mandatory
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@ -210,7 +211,7 @@ say $x; #=> 52
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### Control Flow Structures
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# You don't need to put parenthesis around the condition,
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# but that also means you always have to use brackets (`{ }`) for their body :
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# but that also means you always have to use brackets (`{ }`) for their body:
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## Conditionals
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@ -246,7 +247,7 @@ my $a = $condition ?? $value-if-true !! $value-if-false;
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# blocks, etc), this means the powerful `when` is not only applicable along with
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# a `given`, but instead anywhere a `$_` exists.
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given "foo bar" {
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when /foo/ { # You'll read about the smart-matching operator below -- just know `when` uses it.
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when /foo/ { # Don't worry about smart matching -- just know `when` uses it.
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# This is equivalent to `if $_ ~~ /foo/`.
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say "Yay !";
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}
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@ -262,7 +263,7 @@ given "foo bar" {
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## Looping constructs
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# - `loop` is an infinite loop if you don't pass it arguments,
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# but can also be a c-style `for` :
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# but can also be a c-style `for`:
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loop {
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say "This is an infinite loop !";
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last; # last breaks out of the loop, like the `break` keyword in other languages
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@ -270,8 +271,8 @@ loop {
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loop (my $i = 0; $i < 5; $i++) {
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next if $i == 3; # `next` skips to the next iteration, like `continue`
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# in other languages. Note that you can also use postfix conditionals,
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# loops, etc.
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# in other languages. Note that you can also use postfix
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# conditionals, loops, etc.
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say "This is a C-style for loop !";
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}
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@ -292,12 +293,12 @@ for @array {
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for @array {
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# You can...
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next if $_ == 3; # Skip to the next iteration (like `continue` in C-like languages).
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next if $_ == 3; # Skip to the next iteration (`continue` in C-like languages).
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redo if $_ == 4; # Re-do the iteration, keeping the same topic variable (`$_`).
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last if $_ == 5; # Or break out of a loop (like `break` in C-like languages).
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}
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# Note - the "lambda" `->` syntax isn't reserved to `for` :
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# Note - the "lambda" `->` syntax isn't reserved to `for`:
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if long-computation() -> $result {
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say "The result is $result";
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}
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@ -308,12 +309,12 @@ if long-computation() -> $result {
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## Perl 6 operators are actually just funny-looking subroutines, in syntactic
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## categories, like infix:<+> (addition) or prefix:<!> (bool not).
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## The categories are :
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# - "prefix" : before (like `!` in `!True`).
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# - "postfix" : after (like `++` in `$a++`).
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# - "infix" : in between (like `*` in `4 * 3`).
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# - "circumfix" : around (like `[`-`]` in `[1, 2]`).
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# - "post-circumfix" : around, after another term (like `{`-`}` in `%hash{'key'}`)
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## The categories are:
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# - "prefix": before (like `!` in `!True`).
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# - "postfix": after (like `++` in `$a++`).
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# - "infix": in between (like `*` in `4 * 3`).
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# - "circumfix": around (like `[`-`]` in `[1, 2]`).
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# - "post-circumfix": around, after another term (like `{`-`}` in `%hash{'key'}`)
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## The associativity and precedence list are explained below.
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@ -334,7 +335,8 @@ if long-computation() -> $result {
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(1, 2) eqv (1, 3);
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# - `~~` is smart matching
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# For a complete list of combinations, use this table : http://perlcabal.org/syn/S03.html#Smart_matching
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# For a complete list of combinations, use this table:
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# http://perlcabal.org/syn/S03.html#Smart_matching
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'a' ~~ /a/; # true if matches regexp
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'key' ~~ %hash; # true if key exists in hash
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$arg ~~ &bool-returning-function; # `True` if the function, passed `$arg`
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@ -415,7 +417,7 @@ first-of-array(@tail); # Throws an error "Too many positional parameters passed"
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# (which means the array is too big).
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# You can also use a slurp ...
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sub slurp-in-array(@ [$fst, *@rest]) { # you could decide to keep `*@rest` anonymous
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sub slurp-in-array(@ [$fst, *@rest]) { # You could keep `*@rest` anonymous
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say $fst + @rest.elems; # `.elems` returns a list's length.
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# Here, `@rest` is `(3,)`, since `$fst` holds the `2`.
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}
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@ -485,7 +487,7 @@ sub truthy-array(@array) {
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# You can also use the "whatever star" to create an anonymous function
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# (it'll stop at the furthest operator in the current expression)
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my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }`
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my @arrayplus3 = map(*+*+3, @array); # also works. Same as `-> $a, $b { $a + $b + 3 }`
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my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }`
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say (*/2)(4); #=> 2
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# Immediatly execute the function Whatever created.
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say ((*+3)/5)(5); #=> 1.6
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@ -576,7 +578,7 @@ sub foo {
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bar(); # call `bar` in-place
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}
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sub bar {
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say $*foo; # Perl 6 will look into the call stack instead, and find `foo`'s `$*a`,
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say $*foo; # `$*a` will be looked in the call stack, and find `foo`'s,
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# even though the blocks aren't nested (they're call-nested).
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#=> 1
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}
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@ -589,8 +591,9 @@ sub bar {
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# but you have `$.` to get a public (immutable) accessor along with it.
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# (using `$.` is like using `$!` plus a `method` with the same name)
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# (Perl 6's object model ("SixModel") is very flexible, and allows you to dynamically add methods,
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# change semantics, etc -- This will not be covered here, and you should refer to the Synopsis)
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# (Perl 6's object model ("SixModel") is very flexible,
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# and allows you to dynamically add methods, change semantics, etc ...
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# (this will not be covered here, and you should refer to the Synopsis).
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class A {
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has $.field; # `$.field` is immutable.
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@ -685,7 +688,7 @@ class Item does PrintableVal {
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}
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### Exceptions
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# Exceptions are built on top of classes, usually in the package `X` (like `X::IO`).
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# Exceptions are built on top of classes, in the package `X` (like `X::IO`).
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# Unlike many other languages, in Perl 6, you put the `CATCH` block *within* the
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# block to `try`. By default, a `try` has a `CATCH` block that catches
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# any exception (`CATCH { default {} }`).
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@ -709,7 +712,7 @@ die X::AdHoc.new(payload => 'Error !');
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# Packages are a way to reuse code. Packages are like "namespaces", and any
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# element of the six model (`module`, `role`, `class`, `grammar`, `subset`
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# and `enum`) are actually packages. (Packages are the lowest common denomitor)
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# Packages play a big part in a language, especially as Perl is well-known for CPAN,
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# Packages are important - especially as Perl is well-known for CPAN,
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# the Comprehensive Perl Archive Network.
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# You usually don't use packages directly: you use `class Package::Name::Here;`,
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# or if you only want to export variables/subs, you can use `module`:
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@ -719,7 +722,7 @@ module Hello::World { # Bracketed form
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# ... declarations here ...
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}
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module Parse::Text; # file-scoped form
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grammar Parse::Text::Grammar { # A grammar is a fine package, which you could `use`
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grammar Parse::Text::Grammar { # A grammar is a package, which you could `use`
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}
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# NOTE for Perl 5 users: even though the `package` keyword exists,
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@ -841,7 +844,7 @@ say "This code took " ~ (time - CHECK time) ~ "s to run";
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# ... or clever organization:
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sub do-db-stuff {
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ENTER $db.start-transaction; # create a new transaction everytime we enter the sub
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ENTER $db.start-transaction; # New transaction everytime we enter the sub
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KEEP $db.commit; # commit the transaction if all went well
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UNDO $db.rollback; # or rollback if all hell broke loose
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}
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@ -951,7 +954,7 @@ say 5!; #=> 120
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sub infix:<times>(Int $n, Block $r) { # infix in the middle
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for ^$n {
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$r(); # You need the explicit parentheses to call the function in `$r`,
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# else you'd be referring at the variable itself, kind of like with `&r`.
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# else you'd be referring at the variable itself, like with `&r`.
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}
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}
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3 times -> { say "hello" }; #=> hello
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@ -1004,8 +1007,9 @@ postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that)
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# of the element of the list to be passed to the operator),
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# or `Any` if there's none (examples below).
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#
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# Otherwise, it pops an element from the list(s) one at a time, and applies the binary function
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# to the last result (or the list's first element) and the popped element.
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# Otherwise, it pops an element from the list(s) one at a time, and applies
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# the binary function to the last result (or the list's first element)
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# and the popped element.
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#
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# To sum a list, you could use the reduce meta-operator with `+`, i.e.:
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say [+] 1, 2, 3; #=> 6
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@ -1127,15 +1131,15 @@ for <well met young hero we shall meet later> {
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.say if 'B' ff 'B' for <A B C B A>; #=> B B
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# because the right-hand-side was tested
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# directly (and returned `True`).
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# "B"s are still printed since it matched that time
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# "B"s are printed since it matched that time
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# (it just went back to `False` right away).
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.say if 'B' fff 'B' for <A B C B A>; #=> B C B
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# because the right-hand-side wasn't tested until
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# The right-hand-side wasn't tested until
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# `$_` became "C"
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# (and thus did not match instantly).
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# A flip-flop can change state as many times as needed:
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for <test start print this stop you stopped printing start printing again stop not anymore> {
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for <test start print it stop not printing start print again stop not anymore> {
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.say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop",
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#=> "print this printing again"
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}
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@ -1190,8 +1194,8 @@ say so 'a' ~~ / a /; # More readable with some spaces!
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# a regexp. We're converting the result using `so`, but in fact, it's
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# returning a `Match` object. They know how to respond to list indexing,
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# hash indexing, and return the matched string.
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# The results of the match are also available as `$/` (implicitly lexically-scoped).
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# You can also use the capture variables (`$0`, `$1`, ... - starting at 0, not 1 !).
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# The results of the match are available as `$/` (implicitly lexically-scoped).
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# You can also use the capture variables (`$0`, `$1`, ... starting at 0, not 1 !).
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#
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# You can also note that `~~` does not perform start/end checking
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# (meaning the regexp can be matched with just one char of the string),
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@ -1233,7 +1237,7 @@ so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s
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so 'ac' ~~ / a b* c /; # `True`, they're all optional.
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so 'abc' ~~ / a b* c /; # `True`
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so 'abbbbc' ~~ / a b* c /; # `True`
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so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, but can't be something else.
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so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, not replaceable.
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# - `**` - "Quantify It Yourself".
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# If you squint hard enough, you might understand
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@ -1255,7 +1259,7 @@ so 'fooABCABCbar' ~~ / foo [ A B C ] + bar /;
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# But this does not go far enough, because we can't actually get back what
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# we matched.
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# Capture: We can actually *capture* the results of the regexp, using parentheses.
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so 'fooABCABCbar' ~~ / foo ( A B C ) + bar /; # `True`. (we keep `so` here and use `$/` below)
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so 'fooABCABCbar' ~~ / foo ( A B C ) + bar /; # `True`. (using `so` here, `$/` below)
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# So, starting with the grouping explanations.
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# As we said before, our `Match` object is available as `$/`:
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@ -1308,7 +1312,7 @@ sub MAIN($name) { say "Hello, you !" }
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# And since it's a regular Perl 6 sub, you can haz multi-dispatch:
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# (using a "Bool" for the named argument so that we get `--replace`
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# instead of `--replace=1`)
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subset File of Str where *.IO.d; # convert to IO object, then check the file exists
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subset File of Str where *.IO.d; # convert to IO object to check the file exists
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multi MAIN('add', $key, $value, Bool :$replace) { ... }
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multi MAIN('remove', $key) { ... }
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@ -1325,7 +1329,9 @@ multi MAIN('import', File, Str :$as) { ... } # omitting parameter name
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```
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If you want to go further, you can:
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- Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This is probably the greatest source of Perl 6 information, snippets and such.
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- Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful.
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- Check the [source of Perl 6's functions and classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset easier to implement and optimize).
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- Read the [Synopses](perlcabal.org/syn). They explain it from an implementor point-of-view, but it's still very interesting.
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