Perl6::Overview::Data - Data Types
$
list $foo # $foo +$foo # $foo as Num ~$foo # $foo as Str ?$foo # $foo as Bool "$foo" # $foo as Str item $foo # $foo
.chomp # Returns chomped string with a .newline property giving the newline removed .chop .ord .lc .lcfirst .uc .ucfirst .chars # Length in characters .graphs # Length in graphemes .codes # Length in codepoints .bytes # Length in bytes .tr .reverse .split(/sep/) .hex .oct .index .rindex .substr .trans .capitalize
.abs .cos .exp .int .log .rand .sin .sqrt .chr .floor .ceil
@
list @foo # List of elements +@foo # @foo.elems ~@foo # join ' ', @foo ?@foo # ? @foo.elems "@foo[]" # join ' ', @foo @foo[i] # subscript @foo[i, i] # slice @foo[i; i] # multi-dimensional access item @foo # \@foo
.elems # Number of elements .join($sep) .map:{ ... } .grep:{ ... } .pop .push($elem) .shift .unshift($elem) .reverse .sort( { cond }, { cond }, ... ) .kv # return index,value pairs .pairs # return Pair objects instead .uniq
XXX - someone summarize shapes and multi-dimension syntax
ARRAY = LIST [ LIST ] # Array object
(42) # this is neither a list nor an array, # but a scalar (the Num 42) (42,) # this is a one-element list list 42 # this is a one-element list (42,23) # this is a two-element list [] # this is a zero-element array [42] # this is a one-element array [42,] # this is a one-element array [42,23] # this is a two-element array
List construction (via the comma operator, &infix:<,>), does not create containers, meaning that the elements are aliases:
($foo,$bar)[0] =:= $foo; # true ($foo,$bar)[0] = $baz; # $foo changed to $baz
This also means that
(42,23)[0] = 17; # is a fatal error ("can't modify constant") # Similarly, you can't shift(), pop(), unshift() etc. arrays created by # the comma operator: shift (42,23); # dies
By contrast, Array construction by the [] operator, &circumfix:<[ ]>, does create new containers:
[$foo,$bar][0] =:= $foo; # false [$foo,$bar][0] = $baz; # $foo not changed shift [42,23]; # lives (but the Array is discarded after # the operation) my @array = (42,23); shift @array; # works too, as assignment to an array # implicitly creates new containers.
(While in Perl 5 the distinction between lists and arrays was often implicit, this distinction is made explicit Perl 6. Amongst other reasons, this is because Array objects in scalar context is just itself, it's no longer the parentheses which create list context, but a slurpy array in some signature. In Perl 6, the comma operator creates lists, parens are only for grouping:
# Perl 5 sub foo { (1,2,3) } my $scalar = foo(); # 3 my @array = foo(); # (1,2,3) # Perl 6 sub foo { (1,2,3) } my $scalar = foo(); # [1,2,3] my @array = foo(); # (1,2,3)
Also note that list context, i.e. the context supplied by a slurpy array in a signature, automatically flattens arrays and hashes (but not scalars containing array or hash objects):
sub this_provides_list_context (*@things) { @things[0] } my @foo = <a b c>; my @bar = <d e f>; say this_provides_list_context(@foo, @bar); # "a", not the stringification of @foo (which would be "a b c").
The list constructing comma operator supplies this list context:
sub *infix:<,> (*@things) {...}
This also explains why (@foo, @bar) does not create an array containing two elements, but a List containing @foo + @bar items. (Like @foo.concat(@bar) in other languages.))
@foo + @bar
@foo.concat(@bar)
%
list %foo # List of pairs +%foo # +%foo.keys ~%foo # ??? ?%foo # ? %foo.keys "%foo{}" # ??? %foo{k} # subscript %foo{k, k} # slice %foo<> # %foo{<>} %foo<<>> # %foo{<<>>} %foo{k; k} # multi-dimensional access item %foo # \%foo
.delete($key) .exists($key) .keys .values .kv # List of key, value, key, value, ... .pairs # List of Pair having the same Shapes: XXX - help me Constructors: HASH = LIST { PAIR, PAIR, ... } # anonymous object hash( LIST )
list $foo # $foo # object, so doesn't flatten to $k, $v +$foo # ??? ~$foo # ??? ?$foo # ??? "$foo" # ??? item $foo # $foo
.kv # $key, $value .key .value
:key # key => 1 :key{'value'} # key => 'value' \__ thus: :key<>, :key<<>> key => 'value' # key => 'value' (LHS auto-quoted)
Named Anonymous See also class Foo { } class { } oo role Foo { } role { } oo sub foo { } sub { }, or { } sub method foo { } method { } oo, sub macro foo { } sub rule foo { } rule { } rules grammar Foo { } grammar { } rules package Foo { } package { } mod module Foo { } module { } mod
A variable name is '$foo', '@foo', '%foo', etc.
In the symbol table/the lexical pad, links from variable names to their containers are stored.
A variable with ... sigil always points to a ... container: $ --> Scalar @ --> Array % --> Hash & --> Scalar ^ --> Scalar
A scalar container holds a single cell. This cell can either be constant or modifiable. Binding replaces the cell. $a := $b; # $a's cell slot points to $b's cell. $b := $c; # $b's cell slot points to $c's cell. # $a's cell slot still points to what used to be $b's cell.
Array and hash containers hold many cells. Again, binding replaces a cell. @array[$idx] := $b; # @array's cell slot number $idx points to $b's # cell. $b := $c; # $b's cell slot points to $c's sell. # @array's cell slot number $idx still points to # what used to be $b's cell.
Cells hold the actual values, for example the Num 3 or the Str "Pugs".
To summarize: '$foo' entry in the lexical pad points to... the container of '$foo'. The container holds... a cell, which in turn holds... $foo's value.
Examples:
$foo = 42; # '$foo' --> $foo's container --> cell 123 --> Num 42 $bar = \$foo; # '$bar' --> $bar's container --> cell 456 --> Ref --> --> $foo's container --> cell 123 --> Num 42 $grtz = 23; @array = ($foo, $grtz) # '@array' --> @array's container --> # --> [ # 0 --> cell 111 --> Num 42, # 1 --> cell 222 --> Num 23, # ] # (Changing $foo or $grtz does not have an effect on @array yet.) @array[0] := $foo; # '@array' --> @array's container --> # --> [ # 0 --> cell 123 --> Num 42, # 1 --> cell 222 --> Num 23, # ] # (Changing $grtz still does not have an effect on @array. Changing $foo # (by assignment) does have an effect on @array. Re-binding $foo to some # other variable causes further assignments to $foo to have no effect on # @array again.)
=:= tests whether the cell slots of two containers $a and $b point to the same cell.
=:=
$a = 42; # '$a' --> $a's container --> cell 42 --> Num 42 $b = 42; # '$b' --> $b's container --> cell 23 --> Num 42 $a =:= $b; # false, of course $b := $a; # '$b' --> $b's container --> cell 42 --> Num 42
=== tests whether the eternal values of two immutable cells are identical; for two mutable cells, it evaluates the same way as =:=.
===
42 === 42; # true my $a = 42; my $b = 42; $a =:= $b; # false, of course $a === $b; # true (1,2) === (1,2); # true [1,2] === [1,2]; # false
eqv tests whether current snapshots of the values of two mutable cells are identical; for two immutable cells, it evaluates the same way as ===.
eqv
[1,2] eqv [1,2]; # true my $a = [1,2]; my $b = [1,2]; $a === $b; # false, of course $a eqv $b; # true
Method calls on arrays and hashes go to the container, whereas method calls on scalars go to the cell.
$dog.bark(); # method call dispatched to $dog's value, i.e. a Dog object. @array.elems; # method call dispatched to @array's container, an Array object
Using the .VAR postfix macro, you can force a method call to a scalar to go to its container. An example of a method on a scalar is .exists, which tests whether the container's cell slot is nonempty:
sub foo ($a?) { $a.VAR.exists } foo(); # false foo(42); # true
.exists on array and hash containers test whether an element of a given index/name exists:
my @array = (1,2,3); @array.exists(1); # true (@array[1] is 2) @array.exists(3); # false my %hash = (a => 1, b => 2); %hash.exists("a"); # true (%hash<a> is 1) %hash.exists("c"); # false)
(Reading t/operators/binding/*, t/operators/identity.t, and t/operators/value_equivalence.t is strongly recommended.)
To install Perl6::Doc, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Perl6::Doc
CPAN shell
perl -MCPAN -e shell install Perl6::Doc
For more information on module installation, please visit the detailed CPAN module installation guide.