summaryrefslogtreecommitdiffhomepage
path: root/perl6.html.markdown
diff options
context:
space:
mode:
Diffstat (limited to 'perl6.html.markdown')
-rw-r--r--perl6.html.markdown93
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.
+