Help-Site Computer Manuals
  Algorithms & Data Structures   Programming Languages   Revision Control
  Cameras   Computers   Displays   Keyboards & Mice   Motherboards   Networking   Printers & Scanners   Storage
  Windows   Linux & Unix   Mac


Synopsis_29 - Functions


Synopsis_29 - Functions


Rod Adams <>


 Maintainer:    Larry Wall <>

 Date:          12 Mar 2005

 Last Modified: 23 Feb 2006

 Version:       1

This document attempts to document the list of builtin functions in Perl 6. It assumes familiarity with Perl 5 and prior synopses.

The document is now the official S29. It's still here in the pugs repository temporarily to allow easy access to pugs implementors, but eventually it will be copied over to -law


In Perl 6, all builtin functions belong to a named package. Not all functions are guaranteed to be imported into the global package ::*. In addition, the list of functions imported into ::* will be subject to change with each release of Perl. Authors wishing to ``Future Proof'' their code should either specifically import the functions they will be using, or always refer to the functions by their full name.

After 6.0.0 comes out, global aliases will not be removed lightly, and will never be removed at all without having gone through a deprecation cycle of at least a year. In any event, you can specify that you want the interface for a particular version of Perl, and that can be emulated by later versions of Perl to the extent that security updates allow.

Where code is given here, it is intended to define semantics, not to dictate implementation.

Type Declarations

The following type declarations are assumed:

The root class of all ``character'' types, regardless of level.

This is a subtype of Str, limited to a length of 1 at it's highest supported Unicode level.

The type name Char is aliased to the maximum supported Unicode level in the current lexical scope (where ``current'' is taken to mean the eventual lexical scope for generic code (roles and macros), not the scope in which the generic code is defined). In other words, use Char when you don't care which level you're writing for.

Subclasses (things that are isa AnyChar):

LinguaChar or Ling (language-defined characters)
GraphemeChar or Graf (language-independent graphemes)
CodePoint or Uni (Unicode codepoints)
Yes, Byte is both a string and a number.


 subset MatchTest of Item | Junction;

Used to supply a test to match against. Assume ~~ will be used against it.

Function Packages



 our Num multi Num::abs ( Num $x )

 our Num multi Math::Basic::abs ( Num $x = $+_ )

Absolute Value.


 our Int multi Num::floor ( Num $x )

Returns the highest integer not greater than $x.


 our Int multi Num::ceiling ( Num $x )

 &Num::ceil ::= &Num::ceiling;

Returns the lowest integer not less than $x.


 our Int multi Num::round ( Num $x )

 our Int multi Int ( Num $x )

Returns the nearest integer to $x. The algorithm is floor($x + 0.5). (Other rounding algorithms will be given extended names beginning with ``round''.)


 our Int multi Num::truncate ( Num $x )

 our &Num::int ::= &Num::truncate;

Returns the closest integer to $x whose absolute value is not greater than the absolute value of $x. (In other words, just chuck any fractional part.) This is the default rounding function used by an int() cast, for historic reasons. But see Int constructor above for a rounded version.


 our Num multi Num::exp         ( Num $exponent:       Num :$base = Num::e )

 our Num multi Math::Basic::exp ( Num $exponent = $+_, Num :$base = Num::e )

Performs similar to $base ** $exponent. $base defaults to the constant e.


 our Num multi Num::log         ( Num $x:       Num :$base )

 our Num multi Math::Basic::log ( Num $x = $+_, Num :$base )

Logarithm of base $base, default Natural. Calling with $x == 0 is an error.


 &log10 := &log.assuming:base(10);

 our Num multi Math::Basic::rand ( Num $x = 1 )

Pseudo random number in range 0 ..^ $x. That is, 0 is theoretically possible, while $x is not.


 our Int multi Num::sign ( Num  $x )

 our Int multi Math::Basic::sign ( Num $x = $+_ )

   if !defined($x) { return undef };

   if $x < 0       { return -1    };

   if $x > 0       { return  1    };

   if $x == 0      { return  0    };



or more succinctly:

 our Int multi Math::Basic::sign ( Num $x = $+_ )

   $x <=> 0;


 multi Math::Basic::srand ( Num $seed = default_seed_algorithm())

Seed the generator rand uses. $seed defaults to some combination of various platform dependent characteristics to yield a non-deterministic seed. Note that you get one srand() for free when you start a Perl program, so you must call srand() yourself if you wish to specify a deterministic seed (or if you wish to be differently nondeterministic).


 our Num     multi Num::sqrt ( Num  $x )

 our Complex multi Complex::sqrt ( Num  $x )

 our Complex multi Complex::sqrt ( Complex  $x )

 our Num     multi Math::Basic::sqrt ( Num $x = $+_ )

$x ** 0.5


 constant Num Num::e = exp(1);

 constant Num Num::pi = atan(1,1) * 4;

 constant Int Int::pi = 3;

 constant Complex Complex::i = Complex::sqrt(-1);

 constant Int Int::one = round(-e ** (-i * pi));        # :-)


Standard Trig Functions

 our Num multi Num::func ( Num  $x            : :$base = 'radians' )

 our Num multi Math::Trig::func ( Num $x = $+_, :$base = 'radians' )

where func is one of: sin, cos, tan, asin, acos, atan, sec, cosec, cotan, asec, acosec, acotan, sinh, cosh, tanh, asinh, acosh, atanh, sech, cosech, cotanh, asech, acosech, acotanh.

Performs the various trigonmetric functions.

Option :$base is used to declare how you measure your angles. Given the value of an arc representing a single full revolution.

 $base          Result

 ----           -------

 /:i ^r/        Radians  (2*pi)

 /:i ^d/        Degrees  (360)

 /:i ^g/        Gradians (400)

 Num            Units of 1 revolution.

Note that module currying can be used within a lexical scope to specify a consistent base so you don't have to supply it with every call:

 my module Trig ::= Math::Trig.assuming(:base<degrees>);

This overrides the default of ``radians''.


 our Num multi Math::Trig::atan2 ( Num $y, Num $x = 1 : Num :$base )

This second form of atan computes the arctangent of $y/$x, and takes the quadrant into account. Otherwise behaves as other trigonometric functions.

[Note: changed atan back to atan2, or the default $x = 1 will confuse MMD. The other alternative would be to remove the default. --law]



 our List multi method Array::delete (@array : *@indices )

Sets elements specified by @indices in the invocant to a non-existent state, as if they never had a value. Deleted elements at the end of an Array shorten the length of the Array, unless doing so would violate an is shape() definition.

@indices is interpreted the same way as subscripting is in terms of slices and multidimensionality. See Synopsis 9 for details.

Returns the value(s) previously held in deleted locations.

An unary form is expected. See Hash::delete.


 our Bool multi method Array::exists (@array : Int *@indices )

True if the specified Array element has been assigned to. This is not the same as being defined.

Supplying a different number of indices than invocant has dimensions is an error.

An unary form is expected. See Hash::delete.


 &Array::pop := &Array::splice.assuming(:offset(-1) :length(1));

 our Scalar multi Array::pop (   )

   Array::pop @+_;


 our Int multi Array::push ( @array is rw : *@values )

   Array::splice(@array, @array.elems, 0, @values);



 &Array::shift := &Array::splice.assuming(:offset(0) :length(1));

 our Scalar multi Array::shift (   )

   Array::shift @+_;


 multi List Array::splice ( @array is rw 

                                 : Int $offset = 0,

                                   Int $length,

                                       *@values ) is rw

Behaves similar as Perl 5 splice.

If @array is multidimensional, splice operates only on the first dimension, and works with Array References.


 our Int multi Array::unshift ( @array is rw : *@values )

   Array::splice(@array, 0, 0, @values);



 multi Int|List Array::keys ( @array : MatchTest *@indextests )

 multi Int|List Array::kv ( @array : MatchTest *@indextests )

 multi Int|(List of Pair) Array::pairs  (@array : MatchTest *@indextests )

 multi Int|List Array::values ( @array : MatchTest *@indextests )

(XXX these signatures are wrong. -luqui)

Iterates the elements of @array, in order.

If @indextests are provided, only elements whose indices match $index ~~ any(@indextests) are iterated.

What is returned at each element of the iteration varies with function. values returns the value of the associated element; kv returns a 2 element list in (index, value) order, pairs a Pair(index, value).

@array is considered single dimensional. If it is in fact multi- dimensional, the values returned will be array references to the sub array.

In Scalar context, they all return the count of elements that would have been iterated.



 our Lazy multi Array::grep ( @values :      Code *&test )

 our Lazy multi Array::grep ( @values :  MatchTest $test )

 our Lazy multi List::grep ( MatchTest $test :   *@values )

   gather {

     for @values -> $x {

       take $x if $x ~~ $test;




 our Str multi Array::join ( @values :  Str $delimiter )

 our Str multi List::join ( Str $delimiter : *@values )

   my $str = ~@values[0];

   for 1..@values.end {

     $str ~= $delimiter ~ @values[$_];




 &join := &join.assuming:delimiter(' ');

 our Lazy multi Array::map ( @values : Code *&expression )

 our Lazy multi List::map ( Code $expression : *@values )

   gather {

     while @values {

       take $expression

          .( splice(@values, 0, $expression.arity) );




 our Scalar multi Array::reduce ( @values : Code *&expression )

 our Scalar multi List::reduce ( Code $expression : *@values )

   my $res;

   for @values -> $cur {

        FIRST {$res = $cur; next;}

     $res = &$expression($res, $cur);




 our Hash multi Hash::reverse ( %hash )

   (my %result){%hash.values} = %hash.keys;



 multi Lazy|Str Array::reverse ( @values )

 multi Lazy|Str List::reverse ( *@values )

   given want {

     when List {

       gather {

         1 while take pop @values;



     when Scalar {

       reverse @values ==> join;




 subset KeyExtractor of Code(Any --> Any);

 subset Comparator   of Code(Any, Any --> Int );

 subset SortCriterion of KeyExtractor | Comparator | Pair(KeyExtractor, Comparator);

 our Array multi Array::sort( @values is rw, *&by:                              Bit :$inplace )

 our Array multi Array::sort( @values is rw, SortCriterion @by:                 Bit :$inplace )

 our Array multi Array::sort( @values is rw: SortCriterion :$by = &infix:<cmp>, Bit :$inplace )

 our List multi List::sort( SortCriterion @by:  *@values )

 our List multi List::sort( SortCriterion $by = &infix:<cmp>, *@values )

Returns @values sorted, using criteria $by or @by for comparisons. @by differs from $by in that each criteria is applied, in order, until a non-zero (tie) result is achieved.

Criterion can take a few different forms:

A closure with arity of 2, which returns negative/zero/positive, signaling the first arguement should be before/tied with/after the second in the final ordering of the List. aka ``The Perl 5 way''

A closure with arity of 1, which returns the ``key'' by which to sort. If the closure returns a Num, <=> is used for comparison, otherwise cmp.

Pair(KeyExtractor, Comparator)
A combination of the two methods above, for when one wishs to take advantage of the internal caching of keys that is expected to happen, but wishes to compare them with something other than <=> or cmp.

Any Criterion may recieve either or both of the traits is descending and is insensitive to reverse the order of sort, or the adjust the case sensitivity of cmp as a Comparator.

If all criteria are exhausted when comparing two elements, sort should return them in the same relative order they had in @values.

If $inplace is specified, the array is sorted in place.

See for more details and examples.


 our Lazy multi List::zip ( Array *@lists, Bit :$shortest ) {

   gather {

     while $shortest ?? all(@lists) !! any(@lists) {

       for @lists -> @list {

         take shift @list;





[Note: This should be the definition of each() now. The zip function needs to build tuples of the ``across'' values. Also, it maybe probably be in terms of longest non-infinite. -law]



 our List  multi method Hash::delete ( *@keys )

 our Scalar multi method Hash::delete ( $key ) is default

Deletes the elements specified by $key or $keys from the invocant. returns the value(s) that were associated to those keys.

Unary Form
Implementations should create a suitable macro, or otherwise support the unary form delete %hash{$key} in all its forms. Below are some example translations. This list is not exhaustive.

 delete %hash{$key}                %hash.delete{$key}

 delete %hash<key>                 %hash.delete{'key'}

 delete %hash<key1>{@keys}         %hash<key1>.delete{@keys}


 our Bool multi method Hash::exists ( $key )

True if invocant has an element whose key matches $key, false otherwise.

A unary form is expected. See Hash::delete.

See also Code::exists to determine if a function has been declared. (Use defined() to determine whether the function body is defined. A body of ... counts as undefined.)


 multi Int|List Hash::keys ( %hash : MatchTest *@keytests )

 multi Int|List Hash::kv ( %hash : MatchTest *@keytests )

 multi Int|(List of Pair) Hash::pairs  (%hash : MatchTest *@keytests )

 multi Int|List Hash::values ( %hash : MatchTest *@keytests )


Iterates the elements of C<%hash> in no apparent order, but the order

will be the same between successive calls to these functions, as long as

C<%hash> doesn't change.

If @keytests are provided, only elements whose keys evaluate $key ~~ any(@keytests) as true are iterated.

What is returned at each element of the iteration varies with function. keys only returns the key; values the value; kv returns both as a 2 element list in (key, value) order, pairs a Pair(key, value).

Note that kv %hash returns the same as zip(keys %hash; values %hash)

In Scalar context, they all return the count of elements that would have been iterated.

The lvalue form of keys is not longer supported. Use the .buckets property instead.


General notes about strings:

A Str can exist at several Unicode levels at once. Which level you interact with typically depends on what your current lexical context has declared the ``working unicode level to be''. Default is GChar.

[Q: Default can't be LChar because we don't go into ``language'' mode unless there's a specific language declaration saying either exactly what language we're going into, or what environmental parameter to pay attention to to select our language. So I believe the default should be GChar. -law]

Attempting to use a string at a level higher it can support is handled without warning. The current highest supported level of the string is simply mapped Char for Char to the new higher level. However, attempting to stuff something of a higher level a lower-level string is an error (for example, attempting to store Kanji in a Byte string). And explicit conversion function must be used to tell it how you want it encoded.

Attempting to use a string at a level lower than what it supports is not allowed.

If a function takes a Str and returns a Str, the returned Str will support the same levels as the input, unless specified otherwise.


 our Char multi P5emul::Str::P5chop ( Str  $string is rw )

 our Char multi P5emul::Str::P5chop ( Str *@strings = ($+_) is rw )

Trims the last character from $string, and returns it. Called with a list, it chops each item in turn, and returns the last character chopped.


 our Str method Str::chop ( Str  $string: )

Returns string with one Char removed from the end.


 our Int multi P5emul::Str::P5chomp ( Str  $string is rw )

 our Int multi P5emul::Str::P5chomp ( Str *@strings = ($+_) is rw )

Related to P5chop, only removes trailing chars that match /\n/. In either case, it returns the number of chars removed.


 our Str method Str::chomp ( Str $string: )

Returns string with newline removed from the end. An arbitrary terminator can be removed if the input filehandle has marked the string for where the ``newline'' begins. (Presumably this is stored as a property of the string.) Otherwise a standard newline is removed.

Note: Most users should just let their I/O handles autochomp instead. (Autochomping is the default.)


 our Str multi Str::lc ( Str $string )

 our Str multi Str::lc ( Str $string = $+_ )

Returns the input string after converting each character to its lowercase form, if uppercase.


 our Str multi Str::lcfirst ( Str $string )

 our Str multi Str::lcfirst ( Str $string = $+_ )

Like lc, but only affects the first character.


 our Str multi Str::uc ( Str $string )

 our Str multi Str::uc ( Str $string = $+_ )

Returns the input string after converting each character to its uppercase form, if lowercase. This is not a Unicode ``titlecase'' operation, but a full ``uppercase''.


 our Str multi Str::ucfirst ( Str $string )

 our Str multi Str::ucfirst ( Str $string = $+_ )

Performs a Unicode ``titlecase'' operation on the first character of the string.


 our Str multi Str::capitalize ( Str $string )

 our Str multi Str::capitalize ( Str $string = $+_ )

Has the effect of first doing an lc on the entire string, then performing a s:g/(\w+)/{ucfirst $1}/ on it.

This word is banned in Perl 6. You must specify units.

Needs to be in terms of StrPos, not Int.

Needs to be in terms of StrPos, not Int.


 our List multi Str::split ( Str $delimiter ,  Str $input = $+_, Int $limit = inf )

 our List multi Str::split ( Rule $delimiter = /\s+/,  Str $input = $+_, Int $limit = inf )

 our List multi Str::split ( Str $input :  Str $delimiter          , Int $limit = inf )

 our List multi Str::split ( Str $input : Rule $delimiter          , Int $limit = inf )

String delimiters must not be treated as rules but as constants. The default is no longer ' ' since that would be interpreted as a constant. P5's split(' ') will translate to .words or some such. Null trailing fields are no longer trimmed by default. We might add some kind of :trim flag or introduce a trimlist function of some sort.


 multi substr (Str $s, StrPos $start  : StrPos $end,      $replace)

 multi substr (Str $s, StrPos $start,   StrLen $length  : $replace)

 multi substr (Str $s, StrLen $offset : StrLen $length,   $replace)
Should replace vec with declared arrays of bit, uint2, uint4, etc.


 our List multi Str::words ( Rule $matcher = /\S+/,  Str $input = $+_, Int $limit = inf )

 our List multi Str::words ( Str $input : Rule $matcher = /\S+/, Int $limit = inf )



 multi Control::Basic::eval ( Str $code = $+_, Grammar :$lang = CALLER::<$?PARSER>)

Execute $code as if it were code written in $lang. The default is the language in effect at the exact location of the eval call.

Returns whatever $code returns, or undef on error.


 multi Control::Basic::evalfile (Str $filename : Grammar :$lang = Perl6)

Behaves like, and replaces Perl 5 do EXPR, with optional $lang support.


 multi Control::Basic::exit ( Int $status = 0)

Stops all program execution, and returns $status to the calling environment.


 multi Control::Basic::nothing ()

No operation. Literally does nothing.


 our Num multi Control::Basic::sleep ( Num $for = Inf )

Attempt to sleep for up to $for seconds. Implementations are obligated to support subsecond resolutions if that is at all possible.

[Q: what about multithreading? do we just sleep this thread? need to coordinate with entire async model. -law]

TODO: Research the exception handling system.



Question: I think these should be strictly Code Point level activitities, but I'm not sure. They likely need to be renamed, as well.


 our List multi Conversions::List::list ( *@list )

Forces List Context on it's arguements, and returns them.


 our Item multi Conversions::Item::item ( $item )

Forces generic Item context on its argument, and returns it.

:16, :8, :2, :10

 our Num multi prefix:<:16> ( Str $hexstr = $+_ )

 our Num multi prefix:<:8> ( Str $octstr = $+_ )

 our Num multi prefix:<:2> ( Str $binstr = $+_ )

 our Num multi prefix:<:10> ( Str $decstr = $+_ )


Interprets string as a number, with a default hexadecimal/octal/binary/decimal radix. Any radix prefix (0b, 0d, 0x, 0o) mentioned inside the string will override this operator (this statement is true: 10 == :8 ``0d10''), except 0b and 0d will be interpreted as hex digits by :16 (hex("0d10") == :16 "0d10"). fails on failure.

These aren't really functions, syntactically, but adverbial forms that just happen to allow a parenthesize argument. But more typically you'll see

    :4 "222"

    :16 "deadbeef"

and such.

Replaces Perl 5 hex and oct.






dbmopen, dbmclose

 use DB_File;

See Hash::kv or Hash::pairs instead, and put into for instead of while. Likely there is a Perl5::p5each emulation though.

format, formline, write
See Exegesis 7.


 use IPC::SysV;
There is no ref() any more, since it was almost always used to get the type name in Perl 5. If you really want the type name, you can use $ or $var.^name. If you really want P5 ref semantics, use Perl5::p5ref.

But if you're just wanting to test against a type, you're likely better off performing an isa or does or can, or just $var ~~ TYPE.

Was there a good use for this?




Pending Apocalypse

The following functions are classified by Apocalypse/Synopsis numbers.

A/S14: Tied Variables
tie tied untie (now implemented as container classes? my $foo is ....? is tie the meta operation on the container type for 'rebless' - macro tie ( $var, $class, *@args ) { CODE { variable($var).meta.rebless( $class, *@args ) } } )

These are replaced by container types. The compiler is free to assume that any lexical variable is never going to change its container type unless some representation is made to that effect in the declaration. Note: P5's tied() is roughly replaced by P6's variable().

A/S16: IPC / IO / Signals
-X accept alarm bind binmode chown close closedir connect eof fcntl fileno flock getc getpeername /[get|set][host|net|proto|serv|sock].*/ glob ioctl link listen lstat mkdir open opendir pipe print printf read readdir readline readlink readpipe recv rename rewinddir rmdir seek seekdir select(both) send setsockopt shutdown slurp socket socketpair stat symlink syscall sysopen sysread sysseek syswrite tell telldir truncate umask unlink utime warn

A/S??: OS Interaction
chroot crypt exec getlogin /[get|set][pw|gr].*/ kill setpgrp setpriority system times

... These are probably going to be part of POSIX, automatically imported to GLOBAL iff the platform is the right one

Note: system() should be renamed to sys() or sh() or run() or some such to avoid P5-induced boolean inversion confusion, plus huffmanize it a little better. I'm thinking run() might be best for MMD reasons. --law

Note: exec should also be renamed to something clearer and ``final'' and huffmanly longer. I'm thinking runinstead(). And maybe the function behind qq:x should be rungather() rather than readpipe(). -law

A/S17: Threads and Multiprocessing
fork lock wait waitpid

# FIXME audrey drafted synopsis 17


Please post errors and feedback to perl6-language. If you are making a general laundry list, please separate messages by topic.