Provided by: liblist-maker-perl_0.005-4_all 
NAME
List::Maker - Generate more sophisticated lists than just $a..$b
VERSION
This document describes List::Maker version 0.005
SYNOPSIS
use List::Maker;
@list = <1..10>; # (1,2,3,4,5,6,7,8,9,10)
@list = <10..1>; # (10,9,8,7,6,5,4,3,2,1)
@list = <1,3,..10>; # (1,3,5,7,9)
@list = <1..10 x 2>; # (1,3,5,7,9)
@list = <0..10 : prime N>; # (2,3,5,7)
@list = <1,3,..30 : /7/>; # (7,17,27)
@list = < ^10 >; # (0,1,2,3,4,5,6,7,8,9)
@list = < ^@array >; # (0..$#array)
@words = < a list of words >; # ('a', 'list', 'of', 'words')
@words = < 'a list' "of words" >; # ('a list', 'of words')
use List::Maker 'listify';
@list = listify '1..10'; # (1,2,3,4,5,6,7,8,9,10)
use List::Maker 'make_list';
@list = make_list '10..1'; # (10,9,8,7,6,5,4,3,2,1)
use List::Maker 'ql';
@list = ql'1..10 x 2'; # (1,3,5,7,9)
DESCRIPTION
The List::Maker module hijacks Perl's built-in file globbing syntax ("< *.pl >" and "glob
'*.pl'") and retargets it at list creation.
The rationale is simple: most people rarely if ever glob a set of files, but they have to
create lists in almost every program they write. So the list construction syntax should be
easier than the filename expansion syntax.
Alternatively, you can load the module with an explicit name, and it creates a subroutine
of that name that builds the same kinds of lists for you (leaving the globbing mechanism
unaltered).
INTERFACE
Within any file in which the module has been explicitly loaded:
use List::Maker;
angle brackets no longer expand a shell pattern into a list of files. Instead, they
expand a list specification into a list of values.
Under Perl 5.10 and later the module is also lexically scoped in its effects. That is,
under Perls that support it, the change in the behaviour of angle brackets is confined to
the specific lexical scope into which the module was imported.
Under Perl 5.8 and earlier, loading the module changes the effect of "<...>" and "glob()"
for the remainder of the current package in the current file.
This means:
# Code Under 5.8 or earlier Under 5.10 or later
==================== ==================== ===================
@list = <1..10>; normal glob() normal glob()
{
use List::Maker; installs in file installs in block
@list = <1..10>; generates list generates list
}
@list = <1..10>; generates list normal glob()
Numeric lists
Numeric list specifications may take any of the following forms:
Type Syntax For example Produces
========== =================== =========== ===========
Count up <MIN..MAX> <1..5> (1,2,3,4,5)
Count down <MAX..MIN> <5..1> (5,4,3,2,1)
Count to < ^LIMIT > < ^5 > (0,1,2,3,4)
Count by <START..END x STEP> <1..10 x 3> (1,4,7,10)
Count via <START, NEXT,..END> <1, 3,..10> (1,3,5,7,9)
The numbers don't have to be integers either:
@scores = <0.5..4.5>; # same as: (0.5, 1.5, 2.5, 3.5, 4.5)
@steps = <1..0 x -0.2>; # same as: (1, 0.8, 0.6, 0.4, 0.2, 0)
Filtered numeric lists
Any of the various styles of numeric list may also have a filter applied to it, by
appending a colon, followed by a boolean expression:
@odds = <1..100 : \$_ % 2 != 0 >;
@primes = <3,5..99> : is_prime(\$_) >;
@available = < ^$max : !allocated{\$_} >
@ends_in_7 = <1..1000 : /7$/ >
The boolean expression is tested against each element of the list, and only those for
which it is true are retained. During these tests each element is aliased to $_. However,
since angle brackets interpolate, it's necessary to escape any explicit reference to $_
within the filtering expression, as in the first three examples above.
That often proves to be annoying, so the module also allows the candidate value to be
referred to using any single uppercase letter (which is replaced with "\$_" when the
filter is applied. So the previous examples could also be written:
@odds = <1..100 : N % 2 != 0 >;
@primes = <3,5..99> : is_prime(N) >;
@available = < ^$max : !allocated{N} >
or (since the specific letter is irrelevant):
@odds = <1..100 : X % 2 != 0 >;
@primes = <3,5..99> : is_prime(I) >;
@available = < ^$max : !allocated{T} >
Randomly selecting from lists
In addition to (or instead of) specifying a filter on a list, you can also select a
specific number of the list's items at random, by appending ":pick" N to the list
specification.
For example:
$N_random_percentages = <0..100 : pick $N >;
@any_three_primes = <3,5..99> : is_prime(I) : pick 3>;
$one_available = < ^$max : !allocated{T} :pick>
The requested number of elements are picked at random, and without replacement. If the
number of elements to be picked is omitted, a single element is randomly picked.
You can also pick with replacement (which is equivalent to rolling some number of M-sided
dice, with one list element on each face), by using ":roll" instead of ":pick":
$N_nonunique_random_percentages = <0..100 : roll $N >;
@three_nonunique_primes = <3,5..99> : is_prime(I) : roll 3>;
$one_available = < ^$max : !allocated{T} :roll>
If the number of elements to be rolled is omitted, a single element is randomly rolled
(which is exactly the same as randomly picking it).
Note that, because each requested "roll" is independent, it's entirely possible for one or
more values to be selected repeatedly.
String lists
Any list specification that doesn't conform to one of the four pattern described above is
taken to be a list of whitespace-separated strings, like a "qw{...}" list:
@words = <Eat at Joe's>; # same as: ( 'Eat', 'at', 'Joe\'s' )
However, unlike a "qw{...}", these string lists interpolate (before listification):
$whose = q{Joe's};
@words = <Eat at $whose>; # same as: ( 'Eat', 'at', 'Joe\'s' )
More interestingly, the words in these lists can be quoted to change the default
whitespace separation. For example:
@names = <Tom Dick "Harry Potter">;
# same as: ( 'Tom', 'Dick', 'Harry Potter' )
Single quotes may be also used, but this may be misleading, since the overall list still
interpolates in that case:
@names = <Tom Dick '$Harry{Potter}'>;
# same as: ( 'Tom', 'Dick', "$Harry{Potter}" )
In a scalar context, any string list is converted to the standard English representation:
$names = <Tom>; # 'Tom'
$names = <Tom Dick>; # 'Tom and Dick'
$names = <Tom Dick 'Harry Potter'>; # 'Tom, Dick, and Harry Potter'
Perl 6 repetition list operator
List::Maker also understands the Perl 6 "xx" listification operator:
@affirmations = <'aye' xx 5>; # ('aye','aye','aye','aye','aye')
Random number generation
The module understands two syntaxes for generating random numbers. It can generate a
random number within a range:
$random = < 2r5.5 >; # 2 <= Random number < 5.5
It can also generate an "NdS" dice roll (i.e. the sum of rolling N dice, each with S
sides):
$roll = < 3d12 >; # Sum of three 12-sided dice
The dice notation cares nothing for the laws of physics or rationality and so it will even
allow you to specify a non-integer number of "fractal dice", each with an non-integer
numbers of sides:
$roll = < 3.7d12.3 >; # Sum of three-point-seven 12.3-sided dice
In a list context, the dice notation returns the results of each of the individual die
rolls (including the partial result of a "fractal" roll)
@rolls = < 3d12 >; # (6, 5, 12)
@rolls = < 3.7d12.3 >; # (6.1256, 5.9876, 12.0012, 0.3768)
The values returned in list context will always add up to the value that would have been
returned in a scalar context.
User-defined syntax via "add_handler"
You can add new syntax variations to the "<...>" format using the "add_handler()"
function:
add_handler($pattern => $sub_ref, $pattern => $sub_ref...);
Each pattern is added to the list of syntax checkers and, if it matches, the corresponding
subroutine is called to furnish the result of the "<...>". User-defined handlers are
tested in the same order that they are defined, but before the standard built-in formats
described above.
ALTERNATE INTERFACE
If an argument is passed to the "use List::Maker" statement, then that argument is used as
the name of a subroutine to be installed in the current package. That subroutine then
expects a single argument, which may be used to generate any of the lists described above.
In other words, passing an argument to "use List::Maker" creates an explicit list-making
subroutine, rather than hijacking the built-in "<..>" and "glob()".
For example:
use List::Maker 'range';
for (range '1..100 x 5') {
print "$_: $result{$_}\n";
}
use List::Maker 'roll';
if (roll '3d12' > 20) {
print "The $creature hits you\n";
}
use List::Maker 'conjoin';
print scalar conjoin @names;
DIAGNOSTICS
"Sequence <%s, %s, %s...> will never reach %s"
The specified numeric list didn't make sense. Typically, because you specified an
increasing list with a negative step size (or vice versa).
CONFIGURATION AND ENVIRONMENT
List::Maker requires no configuration files or environment variables.
DEPENDENCIES
None.
INCOMPATIBILITIES
Using this module normally prevents you from using the built-in behaviours of "<...>" or
"glob()" in any files that directly "use" the module (though files that don't load the
module are unaffected). In files that use the module, you would need to use the
"File::Glob" module directly:
use File::Glob;
my @files = bsd_glob("*.pl");
Alternatively, export the list maker by name (see "ALTERNATE INTERFACE").
BUGS AND LIMITATIONS
The lists generated are not lazy. So this:
for (<1..10000000>) {
...
}
will be vastly slower than:
for (1..10000000) {
...
}
Please report any bugs or feature requests to "bug-list-maker@rt.cpan.org", or through the
web interface at <http://rt.cpan.org>.
AUTHOR
Damian Conway "<DCONWAY@CPAN.org>"
LICENCE AND COPYRIGHT
Copyright (c) 2005, Damian Conway "<DCONWAY@CPAN.org>". All rights reserved.
This module is free software; you can redistribute it and/or modify it under the same
terms as Perl itself. See perlartistic.
DISCLAIMER OF WARRANTY
BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE,
TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE
COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF
ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO
THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE
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