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Move stuff around, again.

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Need to teach it in the right order ...
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Nami-Doc 2014-07-25 11:47:56 +02:00
parent 82d65fb3b2
commit a85a05a139
1 changed files with 123 additions and 124 deletions
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@ -126,7 +126,7 @@ sub with-named($normal-arg, :$named) {
with-named(1, named => 6); #=> 7
with-named(2, :named(5)); #=> 7
with-named(3, :4named); #=> 7
# (special colon pair syntax for numbers)
# (special colon pair syntax for numbers, mainly useful for `:2nd` etc)
with-named(3); # warns, because we tried to use the undefined $named
# in a `+`: by default, named arguments are *optional*
@ -160,53 +160,6 @@ named-def; #=> 5
named-def(:10def); #=> 10
named-def(def => 15); #=> 15
## There's more to come, but we're going to end this paragraph with a really powerful feature:
## Unpacking ! It's the ability to "extract" arrays and keys. It'll work in `my`s and parameters.
my ($a, $b) = 1, 2;
say $a; #=> 1
my ($, $, $c) = 1, 2, 3; # keep the non-interesting anonymous
say $c; #=> 3
my ($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 $snd ! All in all, I'm @array[]."; # (remember the `[]` to interpolate the array)
}
foo(@tail); #=> My first is 2, my second is 3 ! All in all, I'm 1 2
# If you're not using the array itself, you can also keep it anonymous, much like a scalar:
sub first-of-array(@ [$fst]) { $fst }
first-of-array(@small); #=> 1
first-of-array(@tail); # errors with "Too many positional parameters passed" (the array is too big)
# You can also use a slurp ...
sub slurp-in-array(@ [$fst, *@rest]) { # you could decide to keep `*@rest` anonymous
say $fst + @rest.elems;
}
slurp-in-array(@tail); #=> 3
# You could even extract on a slurpy (but it's pretty useless ;-).)
sub fst(*@ [$fst]) { # or simply : `sub fst($fst) { ... }`
say $fst;
}
fst(1); #=> 1
fst(1, 2); # errors with "Too many positional parameters passed"
# Lou can also destructure hashes (and classes, which you'll learn about later !)
sub key-of(% (:value($val), :qua($qua))) {
say "Got val $val, $qua times.";
}
# Then call it with a hash: (you need to keep the brackets for it to be a hash)
key-of({value => 1});
#key-of(%hash); # the same (for an equivalent `%hash`)
# `->`, lambda with arguments, and string interpolation
my &lambda = -> $argument { "The argument passed to this lambda is $argument" }
# 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".
# the assignment operator asks the container on the left to store the value on its right
@ -226,57 +179,6 @@ sub mod() is rw { $x }
mod() = 52; # in this case, the parentheses are mandatory
say $x; #=> 52
# The last expression of a sub is returned automatically (though you may use the `return` keyword, of course):
sub next-index($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 + $b + 3 }`
say (*/2)(4); #=> 2
# Immediatly execute the function Whatever created.
say ((*+3)/5)(5); #=> 1.6
# works even in parens !
# but if you need to have more than one argument (`$_`) 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 }`
### Control Flow Structures
@ -298,11 +200,11 @@ 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'
# - Ternary conditional, "?? !!" (like `x ? y : z` in some other languages)
my $a = $condition ?? $value-if-true !! $value-if-false;
# - `given`-`when` looks like other languages `switch`, but it's much more powerful thanks to smart matching.
# given just puts its argument into `$_`, 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 !";
@ -329,12 +231,12 @@ loop (my $i = 0; $i < 5; $i++) {
say "This is a C-style for loop !";
}
# - `for` - Foreaches an array
# - `for` - Passes through an array
for @array -> $variable {
say "I've found $variable !";
}
# default variable is $_
# default variable is $_ (like a block)
for @array {
say "I've got $_";
}
@ -378,7 +280,7 @@ if long-computation() -> $result {
'a' ne 'b'; # not equal
'a' !eq 'b'; # same as above
# - `eqv` is canonical equivalence
# - `eqv` is canonical equivalence (or "deep equality")
(1, 2) eqv (1, 3);
# - `~~` is smart matching
@ -401,7 +303,7 @@ $arg ~~ &bool-returning-function; # true if the function, passed `$arg` as an ar
# `^` 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
^10; # means 0..^10
# This also allows us to demonstrate that Perl 6 has lazy arrays, using the Whatever Star :
my @array = 1..*; # 1 to Infinite !
@ -422,23 +324,102 @@ say @array[^10]; # you can pass arrays as subscripts and it'll return an array o
$a && $b && $c; # returns the first argument that evaluates to False, or the last argument
$a || $b;
## Sequence operator
# The sequence operator is one of Perl 6's most powerful features :
# it's composed of first, on the left, the list you want Perl 6 to deduce from (and might include a closure),
# and on the right, a value or the predicate for when to stop, or even Whatever for a lazy infinite list
my @list = 1, 2, 3 ... 10; # basic deducing
#my @list = 1, 3, 6 ... 10; # this throws you into an infinite loop, because Perl 6 can't figure out the end
my @list = 1, 2, 3 ...^ 10; # as with ranges, you can exclude the last element (when the predicate matches)
my @list = 1, 3, 9 ... * > 30; # you can use a predicate (with the Whatever Star, here)
my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above)
my @primes = 1, 1, *+* ... *; # lazy infinite list of prime numbers, computed using a closure !
my @primes = 1, 1, -> $a, $b { $a + $b } ... *; # (equivalent to the above)
say @primes[^10]; #=> 1 1 2 3 5 8 13 21 34 55
# Note : as for ranges, once reified, elements aren't re-calculated.
# That's why `@primes[^100]` will take a long time the first time you print it, then be instant
### More on subs !
### More on Subs !
# Perl 6 likes functions. So, in Perl 6, they are very powerful:
## There's more to come, but we're going to end this paragraph with a really powerful feature:
## Unpacking ! It's the ability to "extract" arrays and keys. It'll work in `my`s and parameters.
my ($a, $b) = 1, 2;
say $a; #=> 1
my ($, $, $c) = 1, 2, 3; # keep the non-interesting anonymous
say $c; #=> 3
my ($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 $snd ! All in all, I'm @array[]."; # (remember the `[]` to interpolate the array)
}
foo(@tail); #=> My first is 2, my second is 3 ! All in all, I'm 1 2
# If you're not using the array itself, you can also keep it anonymous, much like a scalar:
sub first-of-array(@ [$fst]) { $fst }
first-of-array(@small); #=> 1
first-of-array(@tail); # errors with "Too many positional parameters passed" (the array is too big)
# You can also use a slurp ...
sub slurp-in-array(@ [$fst, *@rest]) { # you could decide to keep `*@rest` anonymous
say $fst + @rest.elems;
}
slurp-in-array(@tail); #=> 3
# You could even extract on a slurpy (but it's pretty useless ;-).)
sub fst(*@ [$fst]) { # or simply : `sub fst($fst) { ... }`
say $fst;
}
fst(1); #=> 1
fst(1, 2); # errors with "Too many positional parameters passed"
# You can also destructure hashes (and classes, which you'll learn about later !)
sub key-of(% (:value($val), :qua($qua))) {
say "Got val $val, $qua times.";
}
# Then call it with a hash: (you need to keep the brackets for it to be a hash)
key-of({value => 1});
#key-of(%hash); # the same (for an equivalent `%hash`)
## The last expression of a sub is returned automatically (though you may use the `return` keyword, of course):
sub next-index($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)
## You can create a lambda with `-> {}` ("pointy block") or `{}` ("block")
my &lambda = -> $argument { "The argument passed to this lambda is $argument" }
# `-> {}` 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 parser.
# 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
# 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`
}
# 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 + $b + 3 }`
say (*/2)(4); #=> 2
# Immediatly execute the function Whatever created.
say ((*+3)/5)(5); #=> 1.6
# works even in parens !
# but if you need to have more than one argument (`$_`) 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,
@ -448,7 +429,7 @@ say @primes[^10]; #=> 1 1 2 3 5 8 13 21 34 55
multi sub sayit(Int $n) { # note the `multi` keyword here
say "Number: $n";
}
multi sayit(Str $s) } # the `sub` is implicit
multi sayit(Str $s) } # the `sub` is the default
say "String: $s";
}
sayit("foo"); # prints "String: foo"
@ -477,7 +458,7 @@ multi with-or-without-you {
# `is`, for example, is actually a `multi sub` named `trait_mod:<is>`, and it works off that.
# `is rw`, for example, is a dispatch to a function with this signature:
# sub trait_mod:<is>(Routine $r, :$rw!) {}
# (commented because running this would probably lead to some surprising side-effects !)
# (commented because running this would probably lead to some very surprising side-effects !)
### Scoping
@ -844,6 +825,24 @@ postcircumfix:<{ }>(%h, $key, :delete);
## End of the operator list:
## Sequence operator
# The sequence operator is one of Perl 6's most powerful features:
# it's composed of first, on the left, the list you want Perl 6 to deduce from (and might include a closure),
# and on the right, a value or the predicate for when to stop, or even Whatever for a lazy infinite list.
my @list = 1, 2, 3 ... 10; # basic deducing
#my @list = 1, 3, 6 ... 10; # this throws you into an infinite loop, because Perl 6 can't figure out the end
my @list = 1, 2, 3 ...^ 10; # as with ranges, you can exclude the last element (when the predicate matches)
my @list = 1, 3, 9 ... * > 30; # you can use a predicate (with the Whatever Star, here)
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)
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.
# That's why `@primes[^100]` will take a long time the first time you print it, then be instant
## * Sort comparison
# They return one value of the `Order` enum : `Less`, `Same` and `More` (which numerify to -1, 0 or +1).
1 <=> 4; # sort comparison for numerics