diff options
Diffstat (limited to 'perl6.html.markdown')
| -rw-r--r-- | perl6.html.markdown | 156 |
1 files changed, 99 insertions, 57 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index 30468c56..d9dce641 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -37,9 +37,9 @@ my $str2 = "String"; # double quotes allow for interpolation my @array = 1, 2, 3; my @array = 'a', 'b', 'c'; # equivalent to : -my @array = <a b c>; # array of string, delimited by space. similar to perl5's qw, or Ruby's %w +my @array = <a b c>; # array of words, delimited by space. similar to perl5's qw, or Ruby's %w -say @array[2]; # Arrays are 0-indexed +say @array[2]; # Array indices start at 0 -- This is the third element ## - Hashes @@ -68,57 +68,8 @@ my &other-s = sub { say "anonymous function !" } # `->`, lambda with arguments, and string interpolation my &lambda = -> $argument { "The argument passed to this lambda is $argument" } - -# add 3 to each value of an array using map : -map({ $_ + 3 }, @array); # $_ is the implicit argument (the same as for `given` and `for`) - -# a sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`) : -# a block doesn't have a function context (though it can have arguments), which means that if you -# return from it, you're going to return from the parent function, compare: -sub is-in(@array, $elem) { - map({ return True if $_ == $elem }, @array); # this will `return` out of `is-in` -} -sub truthy-array(@array) { - # this will produce an array of `True` and `False` : - # (you can also say `anon sub` for "anonymous subroutine") - map(sub { if $_ { return True } else { return False } }, @array); -} - -# `-> {}` and `{}` are pretty much the same thing, except taht the former can take arguments, -# and that the latter can be mistaken as a hash by the compiler - -# You can also use the "whatever star" to create an anonymous function -# (it'll stop at the furthest operator in the current expression) -map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` -map(*+*+3, @array); # also works. Same as `-> $a, $b { $a + $b + 3 }` -say ((*+3)/5)(5); # immediatly execute the function Whatever created -- works even in parens ! - -# but if you need to have more than one argument (`$_`) 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 - -# Note : those are sorted lexicographically. `{ $^b / $^a }` is like `-> $a, b { $ b / $a }` - -## Multiple Dispatch -# Perl 6 can decide which variant of a `sub` to call based on the type of the arguments, -# or on arbitrary preconditions, using `where` : - -# with types -multi sub sayit(Int $n) { # note the `multi` keyword here - say "Number: $n"; -} -multi sayit(Str $s) } # the `sub` is implicit - say "String: $s"; -} -sayit("foo"); # prints "String: foo" -sayit(True); # fails at *compile time* with "calling 'sayit' will never work with arguments of types ..." - -# with arbitrary precondition : -multi is-big(Int $n where * > 10) { True } -multi is-big(Int $) { False } - -# you can also name these checks, by creating "subsets" : -subset Even of Int where * %% 2; +# We're going to see how powerful Perl 6 subs are just a little down below, after seeing the basics of operators +# and control flow structures ### Containers # In Perl 6, values are actually stored in "containers". @@ -154,7 +105,10 @@ unless False { say "It's not false !"; } -# if (true) say; # Won't work +# You can also use their postfix versions, with the keyword after: +say "Quite truthy" if True; + +# if (true) say; # This doesn't work ! # - Ternary conditional my $a = $condition ?? $value-if-true !! $value-if-false; # `??` and `!!` are like `?` and `:` in other languages' @@ -189,16 +143,15 @@ for @array -> $variable { } # default variable is $_ -for array { +for @array { say "I've got $_"; } -# 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"; } - ### Operators ## Since Perl languages are very much operator-based languages @@ -248,6 +201,17 @@ $arg ~~ &bool-returning-function; # true if the function, passed `$arg` as an ar 3 .. 7; # 3 to 7, both included # `^` on either side them exclusive on that side : 3 ^..^ 7; # 3 to 7, not included (basically `4 .. 6`) +# this also works as a shortcut for `0..^N` +^10; # 0..^10 + +# This also allows us to demonstrate that Perl 6 has lazy arrays : +my @array = 1..*; # 1 to Infinite ! +say @array[^10]; # you can pass arrays as subscripts and it'll return an array of results + # this will print "1 2 3 4 5 6 7 8 9 10" (and not run out of memory !) + +# Warning, though : if you try this example in the REPL and juste put `1..*`, +# Perl 6 will be forced to try and evaluate the whole array (to print it), +# so you'll end with an infinite loop ## * And, Or 3 && 4; # True. Calls `.Bool` on `3` @@ -257,6 +221,84 @@ $arg ~~ &bool-returning-function; # true if the function, passed `$arg` as an ar $a && $b && $c; # returns the first argument that evaluates to False, or the last argument $a || $b; +## Sequence operator +# !TODO! +1, 2, 3 ... 10; + +## More on Subs ! +# Perl 6 likes functions. So, in Perl 6, functions are very powerful: + +## Multiple Dispatch +# Perl 6 can decide which variant of a `sub` to call based on the type of the arguments, +# or on arbitrary preconditions, using `where` : + +# with types +multi sub sayit(Int $n) { # note the `multi` keyword here + say "Number: $n"; +} +multi sayit(Str $s) } # the `sub` is implicit + say "String: $s"; +} +sayit("foo"); # prints "String: foo" +sayit(True); # fails at *compile time* with "calling 'sayit' will never work with arguments of types ..." + +# with arbitrary precondition: +multi is-big(Int $n where * > 10) { True } +multi is-big(Int $) { False } + +# you can also name these checks, by creating "subsets": +subset Even of Int where * %% 2; + + +# The last expression of a sub is returned automatically (though you may use the `return` keyword, of course): +sub next-index($n) { + $n + 1; +} +my $new-n = next-index(3); # $new-n is now 4 +# This is true for everything, except for the looping constructs (due to performance reasons): +# there's no purpose in building a list if we're just going to discard all the results. +# If you still want to build one, you can use the `do` prefix: (or the `gather` prefix, which we'll see later) +sub list-of($n) { + do for ^$n { # note the use of the range-to prefix operator `^` (`0..^N`) + $_ # current loop iteration + } +} +my @list3 = list-of(3); #=> (0, 1, 2) + +# We can, for example, add 3 to each value of an array using map : +my @arrayplus3 = map({ $_ + 3 }, @array); # $_ is the implicit argument (the same as for `given` and `for`) + +# a sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`) : +# a block doesn't have a function context (though it can have arguments), which means that if you +# return from it, you're going to return from the parent function, compare: +sub is-in(@array, $elem) { + # this will `return` out of `is-in` sub + # once the condition evaluated to True, the loop won't be run anymore + map({ return True if $_ == $elem }, @array); +} +sub truthy-array(@array) { + # this will produce an array of `True` and `False` : + # (you can also say `anon sub` for "anonymous subroutine") + map(sub { if $_ { return True } else { return False } }, @array); # returns the correct value, even in a `if` +} + +# `-> {}` and `{}` are pretty much the same thing, except that the former can take arguments, +# and that the latter can be mistaken as a hash by the compiler + +# 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 + $b + 3 }` +say ((*+3)/5)(5); # immediatly execute the function Whatever created -- works even in parens ! + +# but if you need to have more than one argument (`$_`) 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 + +# Note : those are sorted lexicographically. `{ $^b / $^a }` is like `-> $a, b { $ b / $a }` + + + ### Object Model ## Perl 6 has a quite comprehensive object model |