Raku Colons
在 Raku 中到处都是冒号, 我搜集了你在 Raku 中使用冒号的所有方式。
Larry 语言再设计第一定律: 每个人都想要冒号
Larry 语言再设计第二定律: Larry 成为冒号
这些都是主题的变体,尤其是“冒号对”语法主题。如果冒号的两种用法看起来不同,或者在不同的用法上下文中不同,即使它们在技术上是相同的,我更愿意说明这两种用法。
命名空间
# namespace
package A::B { ... }
class A::B { ... }
# Namespace separator
my $x = A::B.new;
# Dynamic namespace
my $x = ::("A::B").new;
# Pseudopackage representing null namespace
say ::;
# Anonymous class
class :: is Int {...}
# Current class in a compile-tiem var
class Who { method myname { say ::?CLASS } }
# Call Int method of Int class
42.Int::Int; # => 42
# Treat package X as a hash
say X::.keys;
绑定
# Binding
my $y := $a;
# Read-only binding
my $z ::= $y;
# Container identify
$y =:= $a; # True
Colon-Pair 语法
# Colon-Pair syntax (often seen as adverbs)
my $x = 'cat';
:foo(5) # 'foo' => 5
:foo('dog') # 'foo' => 'dog'
:foo($x) # 'foo' => 'cat'
# Value word quoting, no interpolation
:foo<bar> # 'foo' => 'bar'
:foo<bar baz> # 'foo' => ('bar', 'baz')
:foo<$x> # 'foo' => '$x'
# Value word quoting with interpolation
:foo<<$x>> # 'foo' => 'cat'
:foo<<$x dog>> # 'foo' => ('cat', 'dog')
# Numeric-prefix extraction
say (:73day) # day => 73
# Default to true value
say (:foo) # 'foo' => True
:foo(True) # 'foo' => True
# False instead of true
say (:!foo) # foo => False
# Var name as key, content as value
my @foo=1,2;
:@foo # foo => [1,2]
:@foo # foo => [1,2]
:$x # x => 'cat'
# Base conversion via colon-pair
say :16("dead") # 57005
# binding pair in sig:
my $a;
sub b (:foo($a)! is rw) { $a = 42};
b(:foo($a));
say $a # 42
类型
# T takes value's type
-> Numeric ::T x { say T }(42); # => (Int)
# Type Smileys
Int:D; # Defined Int
Int:U; # Undefined Int
Signature
# signature literal
my $sig = :(Int $foo);
# signature on Callable &var, not yet implemented
my &f:(Str) = -> Str {};
Operators as Methods
my $a = 1;
$a.infix:["+"](3); # $a + 3
$a.infix:<+>(3); # $a + 3, but shorter with quote brackets
$a.prefix:<++>; # ++$a
$a.postfix:<++>; # ++$a
$a.:<++>; # Shorthand for prefix (no param)
$a.:<+>(3); # Shorthand for infix (param provided)
Regex
# Regex adverb
:i/a/ # Case insensitive, outside
/:i a/ # Case insensitive, inside
# Declare vars in regex scope
my regex foo { :my $var; }
# Backtracking control
# similar ones not yet implemented are :: ::> :::
/ a: b?: c*: /
# One especially interesting example you often (don't) see is :?
/ .*:? / # explicit minimal match
/ .*? / # short version that is usually used has no colon
# Unicode character classes
say so "a" ~~ /<[:Alpha]>/
Misc
# Quote adverb
Q:w(word of the day); # :w adverb
# Precedence dropper
@stuff.map({ $_ + 1 }); # Explicit parameter
@stuff.map: { $_ + 1 }; # Parameters come after ':'
# Invocant marker method invocation
$x.say-hi(names => [<me you>]); # Normal way
say-hi($x: names => [<me you>]); # Invocant marker way
# Declare alternative to 'self' for current-instance in method
method wuzzup($this: $name) { say "WUZZUP $name?!" }
# object hashes, ones with complex keys
my $x = :{ (now) => "when?" };
# longname
sub infix:<ya> { ... }
# Specific uses of longnames
use Foo:from<Perl5>;
# Loop labels
MYLABEL: for ^100 {
for ^200 {
last MYLABEL;
}
}
# Twigil for formal named param for a block (like $^x)
say { $:add ?? $^a + $^b !! $^a - $^b }( 4, 5 ) :!add
# This one is a stretch...
# Colons instead of dashes when you invoke cli commands that use MAIN
sub MAIN ( :$filename ) { ... }
# cmd --filename=file.txt
# cmd :filename=file.txt
# cmd :filename # filename => true
冒号真是令人惊叹! Awesome.
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