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More fixes thanks to @timo++'s feedback.

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Nami-Doc 2014-07-25 23:23:13 +02:00
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@ -24,7 +24,7 @@ Meta-note : the triple pound signs are here to denote headlines, double paragrap
### Variables
# In Perl 6, you declare a lexical variable using `my`
a
# Perl 6 has 4 variable types :
## - Scalars. They represent a single value. They start with a `$`
@ -39,7 +39,7 @@ my $bool = True; # `True` and `False` are Perl 6's boolean
my $inverse = !$bool; # You can invert a bool with the prefix `!` operator
my $forced-bool = so $str; # And you can use the prefix `so` operator which turns its operand into a Bool
## - Arrays. They represent multiple values. They start with `@`
## - Arrays. They represent multiple values. Their name start with `@`.
my @array = 1, 2, 3;
my @array = 'a', 'b', 'c';
@ -51,11 +51,11 @@ 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
## - Hashes. Key-Value Pairs.
# Hashes are actually arrays of Pairs (`Key => Value`), "flattened" to remove duplicated keys.
# Hashes are actually arrays of Pairs (`Key => Value`),
# except they get "flattened", removing duplicated keys.
my %hash = 1 => 2,
3 => 4;
my %hash = autoquoted => "key", # keys are auto-quoted
my %hash = autoquoted => "key", # keys *can* get auto-quoted
"some other" => "value", # trailing commas are okay
;
my %hash = <key1 value1 key2 value2>; # you can also create a hash from an even-numbered array
@ -81,13 +81,15 @@ sub say-hello-to(Str $name) { # you can provide the type of an argument
say "Hello, $name !";
}
# since you can omit parenthesis to call a function with no arguments, you need to use `&` also to capture `say-hello`
# since you can omit parenthesis to call a function with no arguments,
# you need "&" in the name to capture `say-hello`
my &s = &say-hello;
my &other-s = sub { say "anonymous function !" }
# A sub can have a "slurpy" parameter, or "doesn't-matter-how-many"
sub as-many($head, *@rest) { # the `*@` slurpy will basically "take everything else".
# Note: you can have parameters *before* (like here) a slurpy one, but not *after*.
# Note: you can have parameters *before* (like here) a slurpy one,
# but not *after*.
say @rest.join(' / ') ~ " !";
}
say as-many('Happy', 'Happy', 'Birthday'); #=> Happy Birthday !
@ -124,18 +126,22 @@ sub with-named($normal-arg, :$named) {
say $normal-arg + $named;
}
with-named(1, named => 6); #=> 7
# There's one gotcha to be aware of, here:
# If you quote your key, Perl 6 won't be able to see it as compile time,
# and you'll have a single Pair object as a positional paramater.
with-named(2, :named(5)); #=> 7
with-named(3, :4named); #=> 7
# (special colon pair syntax for numbers, mainly useful for `:2nd` etc)
with-named(3); # warns, because we tried to use the undefined $named
# in a `+`: by default, named arguments are *optional*
with-named(3); # warns, because we tried to use the undefined $named in a `+`:
# by default, named arguments are *optional*
# To make a named argument mandatory, you can use `?`'s inverse, `!`
sub with-mandatory-named(:$str!) {
say "$named !";
}
with-mandatory-named(str => "My String"); #=> My String
with-mandatory-named(str => "My String"); #=> My String !
with-mandatory-named; # run time error: "Required named parameter not passed"
with-mandatory-named(3); # run time error: "Too many positional parameters passed"
@ -160,6 +166,9 @@ named-def; #=> 5
named-def(:10def); #=> 10
named-def(def => 15); #=> 15
# -- Note: we're going to learn *more* on subs really soon,
# but we need to grasp a few more things to understand their real power. Ready?
### Containers
# In Perl 6, values are actually stored in "containers".
# the assignment operator asks the container on the left to store the value on its right
@ -176,13 +185,14 @@ sub mutate($n is 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
mod() = 52; # in this case, the parentheses are mandatory (else Perl 6 thinks it's a "term")
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 :
# You don't need to put parenthesis around the condition,
# but that also means you always have to use brackets (`{ }`) for their body :
## Conditionals
@ -204,12 +214,14 @@ say "Quite truthy" if True;
my $a = $condition ?? $value-if-true !! $value-if-false;
# - `given`-`when` looks like other languages `switch`, but it's much more powerful thanks to smart matching.
# given just puts its argument into `$_` (like a block), and `when` uses it using the "smart matching" operator.
# given just puts its argument into `$_` (like a block),
# and `when` uses it using the "smart matching" operator.
given "foo bar" {
when /foo/ { # you'll read about the smart-matching operator below -- just know `when` uses it
say "Yay !";
}
when $_.chars > 50 { # smart matching anything with True gives True, so you can also put "normal" conditionals
when $_.chars > 50 { # smart matching anything with True (`$a ~~ True`) is True,
# so you can also put "normal" conditionals.
say "Quite a long string !";
}
default { # same as `when *` (using the Whatever Star)
@ -325,8 +337,9 @@ $a && $b && $c; # returns the first argument that evaluates to False, or the las
$a || $b;
### More on subs !
# As we said before, Perl 6 has *really* powerful subs.
# We're going to see a few more key concepts that make them better than in any other language :-).
## There's more to come, but we're going to end this paragraph with a really powerful feature:
## Unpacking ! It's the ability to "extract" arrays and keys. It'll work in `my`s and parameters.
my ($a, $b) = 1, 2;
say $a; #=> 1
@ -337,7 +350,8 @@ my ($head, *@tail) = 1, 2, 3; # Yes, it's the same as with "slurpy subs"
my (*@small) = 1;
sub foo(@array [$fst, $snd]) {
say "My first is $fst, my second is $snd ! All in all, I'm @array[]."; # (remember the `[]` to interpolate the array)
say "My first is $fst, my second is $snd ! All in all, I'm @array[].";
# (^ remember the `[]` to interpolate the array)
}
foo(@tail); #=> My first is 2, my second is 3 ! All in all, I'm 1 2
@ -361,6 +375,8 @@ fst(1); #=> 1
fst(1, 2); # errors with "Too many positional parameters passed"
# You can also destructure hashes (and classes, which you'll learn about later !)
# The syntax is basically `%hash-name (:key($variable-to-store-value-in))`.
# The hash can stay anonymous if you only need the values you extracted.
sub key-of(% (:value($val), :qua($qua))) {
say "Got val $val, $qua times.";
}
@ -392,18 +408,19 @@ my &lambda = -> $argument { "The argument passed to this lambda is $argument" }
# We can, for example, add 3 to each value of an array using map:
my @arrayplus3 = map({ $_ + 3 }, @array); # $_ is the implicit argument
# 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
# 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
# this will `return` out of the `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` :
# 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`
map(sub { if $_ { return True } else { return False } }, @array);
# ^ the `return` only returns from the anonymous `sub`
}
# You can also use the "whatever star" to create an anonymous function
@ -419,7 +436,7 @@ say ((*+3)/5)(5); #=> 1.6
# you can also use the implicit argument syntax, `$^` :
map({ $^a + $^b + 3 }, @array); # same as the above
# Note : those are sorted lexicographically. `{ $^b / $^a }` is like `-> $a, b { $ b / $a }`
# Note : those are sorted lexicographically. `{ $^b / $^a }` is like `-> $a, b { $b / $a }`
## Multiple Dispatch
# Perl 6 can decide which variant of a `sub` to call based on the type of the arguments,
@ -501,7 +518,7 @@ sub bar {
## In Perl 6, every field is private, and named `$!attr`, but if you declare it with `$.`,
## you get a public (immutable) accessor along with it.
# (Perl 6's object model ("P6Model") is very flexible, and allows you to dynamically add methods,
# (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 {
@ -552,9 +569,10 @@ class B is A { # inheritance uses `is`
method bar { $.val * 10 } # this shadows A's `bar`
}
my B $b .= new(val => 5); # When you use `my T $var`, `$var` starts off with `T` itself in it, so you can call `new` on it
# (`.=` is just the compound operator composed of the dot-call and of the assignment operator)
#
my B $b .= new(val => 5); # When you use `my T $var`, `$var` starts off with `T` itself in it,
# so you can call `new` on it.
# (`.=` is just the compound operator composed of the dot-call and of the assignment operator
# `$a .= b` is the same as `$a = $a.b`)
# Also note that `BUILD` (the method called inside `new`) will set parent properties too,
# so you can pass `val => 5`
# $b.not-inherited; # This won't work, for reasons explained above
@ -765,7 +783,9 @@ $a ! $b ! $c; # with a list-associative `!`, this is `infix:<>`
## Create your own operators !
# Okay, you've been reading all of that, so I guess I should try to show you something exciting.
# I'll tell you a little secret (actually not): In Perl 6, all operators are actually just funny-looking subroutines.
# I'll tell you a little secret (actually not):
# In Perl 6, all operators are actually just funny-looking subroutines.
# You can declare an operator just like you declare a sub:
sub prefix:<win>($winner) { # refer to the operator categories
# (yes, it's the "words operator" `<>`)
@ -818,8 +838,9 @@ postcircumfix:<{ }>(%h, $key, :delete);
# with great power comes great responsibility)
## Meta operators !
# Oh boy, get ready. Get ready, because we're dwelving deep into the rabbit's hole, and you probably won't want
# to go back to other languages after reading that (I'm sure you don't want to already at that point).
# Oh boy, get ready. Get ready, because we're dwelving deep into the rabbit's hole,
# and you probably won't want to go back to other languages after reading that.
# (I'm guessing you don't want to already at that point).
# - Reduce meta-operator
@ -900,7 +921,8 @@ for <test start print this stop you stopped printing start printing again stop n
#=> "print this printing again"
}
# you might also use a Whatever Star, which is equivalent to `True` for the left side or `False` for the right :
# you might also use a Whatever Star,
# which is equivalent to `True` for the left side or `False` for the right:
for (1, 3, 60, 3, 40, 60) {
.say if $_ > 50 ff *; # Once the flip-flop reached a number greater than 50, it'll never go back to `False`
#=> 60 3 40 60