diff options
Diffstat (limited to 'perl6.html.markdown')
| -rw-r--r-- | perl6.html.markdown | 93 |
1 files changed, 53 insertions, 40 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index fca863af..fe5b197c 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -30,7 +30,7 @@ double paragraphs, and single notes. # In Perl 6, you declare a lexical variable using `my` my $variable; -# Perl 6 has 4 variable types : +# Perl 6 has 4 kinds of variables: ## * Scalars. They represent a single value. They start with a `$` @@ -56,7 +56,8 @@ my @array = <a b c>; # array of words, delimited by space. say @array[2]; # Array indices start at 0 -- This is the third element -say "Interpolate an array using [] : @array[]"; #=> Interpolate an array using [] : a b c +say "Interpolate an array using [] : @array[]"; +#=> Interpolate an array using [] : a b c ## * Hashes. Key-Value Pairs. # Hashes are actually arrays of Pairs (`Key => Value`), @@ -99,7 +100,7 @@ my &s = &say-hello; my &other-s = sub { say "Anonymous function !" } # A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" -sub as-many($head, *@rest) { # The `*@` slurpy will basically "take everything else". +sub as-many($head, *@rest) { # `*@` (slurpy) will basically "take everything else". # Note: you can have parameters *before* (like here) # a slurpy one, but not *after*. say @rest.join(' / ') ~ " !"; @@ -191,7 +192,7 @@ named-def(def => 15); #=> 15 # its right. When passed around, containers are marked as immutable. # Which means that, in a function, you'll get an error if you try to # mutate one of your arguments. -# If you really need to, you can ask for a mutable container using `is rw` : +# If you really need to, you can ask for a mutable container using `is rw`: sub mutate($n is rw) { $n++; say "\$n is now $n !"; @@ -199,7 +200,7 @@ sub mutate($n is rw) { # If what you want is a copy instead, use `is copy`. -# A sub itself returns a container, which means it can be marked as rw : +# A sub itself returns a container, which means it can be marked as rw: my $x = 42; sub mod() is rw { $x } mod() = 52; # in this case, the parentheses are mandatory @@ -210,7 +211,7 @@ say $x; #=> 52 ### Control Flow Structures # You don't need to put parenthesis around the condition, -# but that also means you always have to use brackets (`{ }`) for their body : +# but that also means you always have to use brackets (`{ }`) for their body: ## Conditionals @@ -246,7 +247,7 @@ my $a = $condition ?? $value-if-true !! $value-if-false; # blocks, etc), this means the powerful `when` is not only applicable along with # a `given`, but instead anywhere a `$_` exists. given "foo bar" { - when /foo/ { # You'll read about the smart-matching operator below -- just know `when` uses it. + when /foo/ { # Don't worry about smart matching -- just know `when` uses it. # This is equivalent to `if $_ ~~ /foo/`. say "Yay !"; } @@ -262,7 +263,7 @@ given "foo bar" { ## Looping constructs # - `loop` is an infinite loop if you don't pass it arguments, -# but can also be a c-style `for` : +# but can also be a c-style `for`: loop { say "This is an infinite loop !"; last; # last breaks out of the loop, like the `break` keyword in other languages @@ -270,8 +271,8 @@ loop { loop (my $i = 0; $i < 5; $i++) { next if $i == 3; # `next` skips to the next iteration, like `continue` - # in other languages. Note that you can also use postfix conditionals, - # loops, etc. + # in other languages. Note that you can also use postfix + # conditionals, loops, etc. say "This is a C-style for loop !"; } @@ -292,12 +293,12 @@ for @array { for @array { # You can... - next if $_ == 3; # Skip to the next iteration (like `continue` in C-like languages). + next if $_ == 3; # Skip to the next iteration (`continue` in C-like languages). redo if $_ == 4; # Re-do the iteration, keeping the same topic variable (`$_`). last if $_ == 5; # Or break out of a loop (like `break` in C-like languages). } -# Note - the "lambda" `->` syntax isn't reserved to `for` : +# Note - the "lambda" `->` syntax isn't reserved to `for`: if long-computation() -> $result { say "The result is $result"; } @@ -308,12 +309,12 @@ if long-computation() -> $result { ## Perl 6 operators are actually just funny-looking subroutines, in syntactic ## categories, like infix:<+> (addition) or prefix:<!> (bool not). -## The categories are : -# - "prefix" : before (like `!` in `!True`). -# - "postfix" : after (like `++` in `$a++`). -# - "infix" : in between (like `*` in `4 * 3`). -# - "circumfix" : around (like `[`-`]` in `[1, 2]`). -# - "post-circumfix" : around, after another term (like `{`-`}` in `%hash{'key'}`) +## The categories are: +# - "prefix": before (like `!` in `!True`). +# - "postfix": after (like `++` in `$a++`). +# - "infix": in between (like `*` in `4 * 3`). +# - "circumfix": around (like `[`-`]` in `[1, 2]`). +# - "post-circumfix": around, after another term (like `{`-`}` in `%hash{'key'}`) ## The associativity and precedence list are explained below. @@ -334,7 +335,8 @@ if long-computation() -> $result { (1, 2) eqv (1, 3); # - `~~` is smart matching -# For a complete list of combinations, use this table : http://perlcabal.org/syn/S03.html#Smart_matching +# For a complete list of combinations, use this table: +# http://perlcabal.org/syn/S03.html#Smart_matching 'a' ~~ /a/; # true if matches regexp 'key' ~~ %hash; # true if key exists in hash $arg ~~ &bool-returning-function; # `True` if the function, passed `$arg` @@ -415,7 +417,7 @@ first-of-array(@tail); # Throws an error "Too many positional parameters passed" # (which means the array is too big). # You can also use a slurp ... -sub slurp-in-array(@ [$fst, *@rest]) { # you could decide to keep `*@rest` anonymous +sub slurp-in-array(@ [$fst, *@rest]) { # You could keep `*@rest` anonymous say $fst + @rest.elems; # `.elems` returns a list's length. # Here, `@rest` is `(3,)`, since `$fst` holds the `2`. } @@ -485,7 +487,8 @@ sub truthy-array(@array) { # You can also use the "whatever star" to create an anonymous function # (it'll stop at the furthest operator in the current expression) my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` -my @arrayplus3 = map(*+*+3, @array); # also works. Same as `-> $a, $b { $a + $b + 3 }` +my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }` + # also `sub ($a, $b) { $a + $b + 3 }` say (*/2)(4); #=> 2 # Immediatly execute the function Whatever created. say ((*+3)/5)(5); #=> 1.6 @@ -494,7 +497,8 @@ say ((*+3)/5)(5); #=> 1.6 # But if you need to have more than one argument (`$_`) # in a block (without wanting to resort to `-> {}`), # you can also use the implicit argument syntax, `$^` : -map({ $^a + $^b + 3 }, @array); # same as the above +map({ $^a + $^b + 3 }, @array); # equivalent to following: +map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) # Note : those are sorted lexicographically. # `{ $^b / $^a }` is like `-> $a, $b { $b / $a }` @@ -576,7 +580,7 @@ sub foo { bar(); # call `bar` in-place } sub bar { - say $*foo; # Perl 6 will look into the call stack instead, and find `foo`'s `$*a`, + say $*foo; # `$*a` will be looked in the call stack, and find `foo`'s, # even though the blocks aren't nested (they're call-nested). #=> 1 } @@ -589,8 +593,9 @@ sub bar { # but you have `$.` to get a public (immutable) accessor along with it. # (using `$.` is like using `$!` plus a `method` with the same name) -# (Perl 6's object model ("SixModel") is very flexible, and allows you to dynamically add methods, -# change semantics, etc -- This will not be covered here, and you should refer to the Synopsis) +# (Perl 6's object model ("SixModel") is very flexible, +# and allows you to dynamically add methods, change semantics, etc ... +# (this will not be covered here, and you should refer to the Synopsis). class A { has $.field; # `$.field` is immutable. @@ -685,7 +690,7 @@ class Item does PrintableVal { } ### Exceptions -# Exceptions are built on top of classes, usually in the package `X` (like `X::IO`). +# Exceptions are built on top of classes, in the package `X` (like `X::IO`). # Unlike many other languages, in Perl 6, you put the `CATCH` block *within* the # block to `try`. By default, a `try` has a `CATCH` block that catches # any exception (`CATCH { default {} }`). @@ -709,7 +714,7 @@ die X::AdHoc.new(payload => 'Error !'); # Packages are a way to reuse code. Packages are like "namespaces", and any # element of the six model (`module`, `role`, `class`, `grammar`, `subset` # and `enum`) are actually packages. (Packages are the lowest common denomitor) -# Packages play a big part in a language, especially as Perl is well-known for CPAN, +# Packages are important - especially as Perl is well-known for CPAN, # the Comprehensive Perl Archive Network. # You usually don't use packages directly: you use `class Package::Name::Here;`, # or if you only want to export variables/subs, you can use `module`: @@ -719,7 +724,7 @@ module Hello::World { # Bracketed form # ... declarations here ... } module Parse::Text; # file-scoped form -grammar Parse::Text::Grammar { # A grammar is a fine package, which you could `use` +grammar Parse::Text::Grammar { # A grammar is a package, which you could `use` } # NOTE for Perl 5 users: even though the `package` keyword exists, @@ -841,7 +846,7 @@ say "This code took " ~ (time - CHECK time) ~ "s to run"; # ... or clever organization: sub do-db-stuff { - ENTER $db.start-transaction; # create a new transaction everytime we enter the sub + ENTER $db.start-transaction; # New transaction everytime we enter the sub KEEP $db.commit; # commit the transaction if all went well UNDO $db.rollback; # or rollback if all hell broke loose } @@ -951,7 +956,7 @@ say 5!; #=> 120 sub infix:<times>(Int $n, Block $r) { # infix in the middle for ^$n { $r(); # You need the explicit parentheses to call the function in `$r`, - # else you'd be referring at the variable itself, kind of like with `&r`. + # else you'd be referring at the variable itself, like with `&r`. } } 3 times -> { say "hello" }; #=> hello @@ -1004,8 +1009,9 @@ postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) # of the element of the list to be passed to the operator), # or `Any` if there's none (examples below). # -# Otherwise, it pops an element from the list(s) one at a time, and applies the binary function -# to the last result (or the list's first element) and the popped element. +# Otherwise, it pops an element from the list(s) one at a time, and applies +# the binary function to the last result (or the list's first element) +# and the popped element. # # To sum a list, you could use the reduce meta-operator with `+`, i.e.: say [+] 1, 2, 3; #=> 6 @@ -1068,6 +1074,11 @@ my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above) my @fib = 1, 1, *+* ... *; # lazy infinite list of prime numbers, # computed using a closure! my @fib = 1, 1, -> $a, $b { $a + $b } ... *; # (equivalent to the above) +my @fib = 1, 1, { $^a + $^b } ... *; #(... also equivalent to the above) +# $a and $b will always take the previous values, meaning here +# they'll start with $a = 1 and $b = 1 (values we set by hand). +# then $a = 1 and $b = 2 (result from previous $a+$b), and so on. + say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 # (using a range as the index) # Note : as for ranges, once reified, elements aren't re-calculated. @@ -1127,15 +1138,15 @@ for <well met young hero we shall meet later> { .say if 'B' ff 'B' for <A B C B A>; #=> B B # because the right-hand-side was tested # directly (and returned `True`). - # "B"s are still printed since it matched that time + # "B"s are printed since it matched that time # (it just went back to `False` right away). .say if 'B' fff 'B' for <A B C B A>; #=> B C B - # because the right-hand-side wasn't tested until + # The right-hand-side wasn't tested until # `$_` became "C" # (and thus did not match instantly). # A flip-flop can change state as many times as needed: -for <test start print this stop you stopped printing start printing again stop not anymore> { +for <test start print it stop not printing start print again stop not anymore> { .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", #=> "print this printing again" } @@ -1190,8 +1201,8 @@ say so 'a' ~~ / a /; # More readable with some spaces! # a regexp. We're converting the result using `so`, but in fact, it's # returning a `Match` object. They know how to respond to list indexing, # hash indexing, and return the matched string. -# The results of the match are also available as `$/` (implicitly lexically-scoped). -# You can also use the capture variables (`$0`, `$1`, ... - starting at 0, not 1 !). +# The results of the match are available as `$/` (implicitly lexically-scoped). +# You can also use the capture variables (`$0`, `$1`, ... starting at 0, not 1 !). # # You can also note that `~~` does not perform start/end checking # (meaning the regexp can be matched with just one char of the string), @@ -1233,7 +1244,7 @@ so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s so 'ac' ~~ / a b* c /; # `True`, they're all optional. so 'abc' ~~ / a b* c /; # `True` so 'abbbbc' ~~ / a b* c /; # `True` -so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, but can't be something else. +so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, not replaceable. # - `**` - "Quantify It Yourself". # If you squint hard enough, you might understand @@ -1255,7 +1266,7 @@ so 'fooABCABCbar' ~~ / foo [ A B C ] + bar /; # But this does not go far enough, because we can't actually get back what # we matched. # Capture: We can actually *capture* the results of the regexp, using parentheses. -so 'fooABCABCbar' ~~ / foo ( A B C ) + bar /; # `True`. (we keep `so` here and use `$/` below) +so 'fooABCABCbar' ~~ / foo ( A B C ) + bar /; # `True`. (using `so` here, `$/` below) # So, starting with the grouping explanations. # As we said before, our `Match` object is available as `$/`: @@ -1308,7 +1319,7 @@ sub MAIN($name) { say "Hello, you !" } # And since it's a regular Perl 6 sub, you can haz multi-dispatch: # (using a "Bool" for the named argument so that we get `--replace` # instead of `--replace=1`) -subset File of Str where *.IO.d; # convert to IO object, then check the file exists +subset File of Str where *.IO.d; # convert to IO object to check the file exists multi MAIN('add', $key, $value, Bool :$replace) { ... } multi MAIN('remove', $key) { ... } @@ -1325,7 +1336,9 @@ multi MAIN('import', File, Str :$as) { ... } # omitting parameter name ``` If you want to go further, you can: + - Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This is probably the greatest source of Perl 6 information, snippets and such. - Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful. - 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). - Read the [Synopses](perlcabal.org/syn). They explain it from an implementor point-of-view, but it's still very interesting. + |