/ 
builtin-0.04
/ builtin

NAME

builtin - A selection of general-utility subroutines

SYNOPSIS

use builtin qw(wanted_subroutines);

DESCRIPTION

builtin contains a selection of subroutines that people have expressed would be nice to have in the perl core, but the usage would not really be high enough to warrant the use of a keyword, and the size so small such that being individual extensions would be wasteful.

By default builtin does not export any subroutines. The subroutines defined are

blessed EXPR

If EXPR evaluates to a blessed reference the name of the package that it is blessed into is returned. Otherwise undef is returned.

dualvar NUMERIC, STRING

Returns a new scalar variable which will act in a similar way to the $! variable. The value of this new variable will be the numerical value of NUMERIC in a numeric context and the string value of STRING in a string context.

$foo = dualvar 10, "Hello";
$num = $foo + 2;			# 12
$str = $foo . " world";		# Hello world
max LIST

Returns the entry in the list with the highest numerical value. If the list is empty then undef is returned.

$foo = max 1..10                # 10
$foo = max 3,9,12               # 12
$foo = max @bar, @baz           # whatever

This function could be implemented using reduce like this

$foo = reduce { $_[0] > $_[1] ? $_[0] : $_[1] } 1..10
maxstr LIST

Similar to max, but treats all the entries in the list as strings and returns the highest string as defined by the gt operator. If the list is empty then undef is returned.

$foo = maxstr 'A'..'Z'     	    # 'Z'
$foo = maxstr "hello","world"   # "world"
$foo = maxstr @bar, @baz        # whatever

This function could be implemented using reduce like this

$foo = reduce { $_[0] gt $_[1] ? $_[0] : $_[1] } 'A'..'Z'
min LIST

Similar to max but returns the entry in the list with the lowest numerical value. If the list is empty then undef is returned.

$foo = min 1..10                # 1
$foo = min 3,9,12               # 3
$foo = min @bar, @baz           # whatever

This function could be implemented using reduce like this

$foo = reduce { $_[0] < $_[1] ? $_[0] : $_[1] } 1..10
minstr LIST

Similar to min, but treats all the entries in the list as strings and returns the lowest string as defined by the lt operator. If the list is empty then undef is returned.

$foo = maxstr 'A'..'Z'     	    # 'A'
$foo = maxstr "hello","world"   # "hello"
$foo = maxstr @bar, @baz        # whatever

This function could be implemented using reduce like this

$foo = reduce { $_[0] lt $_[1] ? $_[0] : $_[1] } 'A'..'Z'
reduce BLOCK LIST
reduce SUBREF, LIST

Reduces LIST by calling BLOCK, or the sub referenced by SUBREF, multiple times with two arguments. The first call will be with the first two elements of the list, subsequent calls will be done by passing the result of the previous call and the next element in the list.

Returns the result of the last call to BLOCK. If LIST is empty then undef is returned. If LIST only contains one element then that element is returned and BLOCK is not executed.

$foo = reduce { $_[0] < $_[1] ? $_[0] : $_[1] } 1..10       # min
$foo = reduce { $_[0] lt $_[1] ? $_[0] : $_[1] } 'aa'..'zz' # minstr
$foo = reduce { $_[0] + $_[1] } 1 .. 10                     # sum
$foo = reduce { $_[0] . $_[1] } @bar                        # concat
sum LIST

Returns the sum of all the elements in LIST.

$foo = sum 1..10                # 55
$foo = sum 3,9,12               # 24
$foo = sum @bar, @baz           # whatever

This function could be implemented using reduce like this

$foo = reduce { $_[0] + $_[1] } 1..10
clock

Returns the time in fractional seconds, to the resolution supplied by the OS. This function is provided as a high resolution replacement for perl's built-in time function, see "time" in perlfunc.

readonly SCALAR

Returns a true value is a read-only variable. This is useful in subroutines that want to modify the arguments, but need to check first if a constant was passed.

NOTE

It should be noted that this module is not intended to be a bit bucket for any sub that some person thinks might be useful. Some general guidelines are to consider if a particular sub should be included in builtin are

The sub is of general use and cannot be implemented in perl.

or

The sub is very commonly used and needs fast implementation in C.

COPYRIGHT

Copyright (c) 1997 Graham Barr <gbarr@pobox.com>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.