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Perl6-Bible-0.16
/ Perl6::Bible::S29

Title

[DRAFT] Synopsis 29 - Builtin Functions [DRAFT]

Version

Maintainer:    Rod Adams <rod@rodadams.net>
Date:          12 Mar 2005
Last Modified: 16 Mar 2005

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

Notes

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.

Function Packages

Math::Basic

abs
multi sub abs (: Num ?$x = $CALLER::_ ) returns Num

Absolute Value.

exp
multi sub exp (: Num ?$exponent = $CALLER::_, Num +$base) returns Num

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

log
multi sub log (: Num ?$x = $CALLER::_, Num +$base) returns Num

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

log10
&log10<> := &log<>.assuming:base(10);
rand
multi sub rand (: Num ?$x = 1, Num +$seed) returns Num

Random Number between 0 and 1, or rand()*$x. Optionally seed the generator with $seed.

sign
multi sub sign (: Num ?$x = $CALLER::_) returns Int {
  if !defined($x) { return undef };
  if $x < 0       { return -1    };
  if $x > 0       { return  1    };
  if $x == 0      { return  0    };
  undef;
}
sqrt
multi sub sqrt (: Num ?$x = $CALLER::_) returns Num

$x ** 0.5

Math::Trig

Standard Trig Functions
multi sub func (: Num ?$x = $CALLER::_, +$base) returns Num

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 your 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.
atan
multi sub atan (Num $x, Num $y : Num +$base) returns Num

This second form of atan computes the arctangent of $y/$x, and takes the quadrant into account. Otherwise behaves as other trigonometric functions. Replaces Perl 5 atan2.

pi
multi sub pi () returns Num

Perl6::Arrays

Note: These package names are pluralized to distinguish them from the classes that will likely assume the singular names.

delete
multi method Perl6::Array::delete (: *@indices) returns List

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 Perl6::Hashes::delete

exists
multi method Perl6::Array::exists (: Int *@indices) returns Bool

Returns 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 Perl6::Hashes::delete

pop
multi sub pop () returns Scalar {
  pop @CALLER::_;
}
&pop<Array> := &splice<Array>.assuming(:offset(-1) :length(1));

Question: is @CALLER::_ the right way to address the caller's slurpy array, per A06?

push
multi sub push (@array is rw : *@values) returns Int {
  splice(@array, @array.elems, 0, @values);
  @array.elems;
}
shift
multi sub shift () returns Scalar {
  shift @CALLER::_;
}
&shift<Array> := &splice<Array>.assuming(:offset(0) :length(1));
splice
multi sub splice (     @array is rw
                : Int ?$offset = 0,
                  Int ?$length,
                      *@values)
  returns List is Lvalue

Behaves the similar as Perl 5 splice.

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

unshift
multi sub unshift (@array is rw : *@values) returns Int {
  splice(@array, 0, 0, @values);
  @array.elems;
}
keys
kv
pairs
values
multi sub keys   (@array : Any|Junction *@indextests) returns Int|List
multi sub kv     (@array : Any|Junction *@indextests) returns Int|List
multi sub pairs  (@array : Any|Junction *@indextests) returns Int|(List of Pair)
multi sub values (@array : Any|Junction *@indextests) returns Int|List

Iterates the elements of @array, in order.

If @indextests are provided, only elements whose indices evaluate $index ~~ any(@indextests) as true 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.

Perl6::Lists

grep
multi sub grep (Any|Junction $test : *@values) returns List {
  gather {
    for @values -> $x {
      take $x if $x ~~ $test;
    }
  }
}
join
multi sub join (Str $delimiter : *@values) returns List {
  my $str = ~@values[0];
  for 1..@values.end {
    $str ~= $delimiter ~ @values[$_];
  }
  $str;
}
&join<> := &join<Str>.assuming:delimiter(' ');
map
multi sub map (Code $expression : *@values) returns List {
  gather {
    while @values {
      take $expression
         .( splice(@values, 0, $expression.arity) );
    }
  }
}
reduce
multi sub reduce (Code $expression : *@values) returns List {
  my $res;
  for @values -> $cur {
       FIRST {$res = $cur; next;}
    $res = &$expression($res, $cur);
  }
  $res;
}
reverse
multi sub reverse (%hash) returns Hash is default {
  my %result;
  for %hash.kv -> $k, $v {
    %result{$v} = $k;
  }
  %result;
}

multi sub reverse (: *@values) returns List|Str {
  given want {
    when List {
      gather {
        1 while take pop @values;
      }
    }
    when Scalar {
      reverse @values ==> join;
    }
  }
}
sort
multi sub sort(Criterion @by : *@values) returns List
multi sub sort(Criterion $by : *@values) returns List
&sort<> := &sort<Criterion>.assuming(by => &infix:<cmp>);

type KeyExtractor ::= Code(Any) returns Any;
type Comparator   ::= Code(Any, Any) returns Int;
type Criterion    ::= KeyExtractor | Comparator
                      | Pair(KeyExtractor, Comparator);

Returns @values sorted, using criteria $by or @by for comparisions. @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:

Comparator

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"

KeyExtractor

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 in 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.

See http://www.nntp.perl.org/group/perl.perl6.language/16578 for more details and examples.

zip
multi sub zip (Array *@lists) returns List {
  gather {
    while any(@lists) {
      for @lists -> @list {
        take shift @list;
      }
    }
  }
}

Example: zip (1,4,7,10 ; 2,5,8,11 ; 3,6) generates (1,2,3,4,5,6,7,8,undef,10,11,undef)

Perl6::Hashes

delete
multi method Hash::delete (: *@keys) returns List
multi method Hash::delete (   $key ) returns Scalar 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 it's 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}

Since different implementations parse in different ways, no general macro will be provided at this time.

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

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

An unary form is expected. See Perl6::Hashes::delete

keys
kv
pairs
values
multi sub keys   (%hash : Any|Junction *@keytests) returns Int|List
multi sub kv     (%hash : Any|Junction *@keytests) returns Int|List
multi sub pairs  (%hash : Any|Junction *@keytests) returns Int|(List of Pair)
multi sub values (%hash : Any|Junction *@keytests) returns Int|List

Iterates the elements of %hash in no apparent order, but the order will be the same between successive calls to these functions, as long as %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.

TODO

chomp
chr
hex
index
lc
lcfirst
length
oct
ord
pack
pos
quotemeta
rindex
split
sprintf
study
substr
uc
ucfirst
unpack
caller
defined
prototype
ref
die
do
eval
exit
sleep
bless
gmtime
localtime
time
undef
vec
want
caller

Obsolete

chop

Use chomp or substr

dbmopen, dbmclose
use DB_File;
dump

With Parrot?

each
while (defined(($key, $value) = each %hash)) { ... }

is now

for %hash.kv -> $key, $value { ... };
format, formline, write

See Exgesis 7.

reset

Was there a good use for this?

scalar EXPR

Use the appropriate / \+ | ~ | \? | int / operator. See S04

Question: Is this correct?

srand

rand(:seed($x))

Pending Apocalypse

The following functions are pending a future Apocalypse/Synopsis/p6l Discussion before progress can be made:

A/S14: Tied Variables

tie tied untie

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 kill link listen lstat mkdir /msg.*/ open opendir pipe print printf read readdir readline readlink readpipe recv rename rewinddir rmdir seek seekdir select(both) /sem.*/ send setsockopt /shm.*/ shutdown 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].*/ setpgrp setpriority system times

A/S17: Threads and Multiprocessing

fork lock wait waitpid

Additions

Is your favorite function, which you spent weeks successfully arguing on perl6-language to get accepted, nowhere on this document? Have no fear. Email rod@rodadams.net with a brief description and a link to the thread on http://www.nntp.perl.org/group/perl.perl6.language, and it'll get listed.

Post errors to perl6-language.