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Revision 67978a2d

Von Moritz Bunkus vor mehr als 10 Jahren hinzugefügt

  • ID 67978a2d5a19e3d2af10a476fb9e0306dda118fc
  • Vorgänger 00ad7b56
  • Nachfolger ac12b284

Modul List::UtilsBy in Abhängigkeiten und als Fallback aufgenommen

Unterschiede anzeigen:

SL/InstallationCheck.pm
{ name => "Image::Info", url => "http://search.cpan.org/~srezic/", debian => 'libimage-info-perl' },
{ name => "JSON", url => "http://search.cpan.org/~makamaka", debian => 'libjson-perl' },
{ name => "List::MoreUtils", version => '0.21', url => "http://search.cpan.org/~vparseval/", debian => 'liblist-moreutils-perl' },
{ name => "List::UtilsBy", url => "http://search.cpan.org/~pevans/", debian => 'liblist-utilsby-perl' },
{ name => "Params::Validate", url => "http://search.cpan.org/~drolsky/", debian => 'libparams-validate-perl' },
{ name => "PDF::API2", version => '2.000', url => "http://search.cpan.org/~areibens/", debian => 'libpdf-api2-perl' },
{ name => "Rose::Object", url => "http://search.cpan.org/~jsiracusa/", debian => 'librose-object-perl' },
doc/modules/LICENSE.List-UtilsBy
This software is copyright (c) 2012 by Paul Evans <leonerd@leonerd.org.uk>.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
Terms of the Perl programming language system itself
a) the GNU General Public License as published by the Free
Software Foundation; either version 1, or (at your option) any
later version, or
b) the "Artistic License"
--- The GNU General Public License, Version 1, February 1989 ---
This software is Copyright (c) 2012 by Paul Evans <leonerd@leonerd.org.uk>.
This is free software, licensed under:
The GNU General Public License, Version 1, February 1989
GNU GENERAL PUBLIC LICENSE
Version 1, February 1989
Copyright (C) 1989 Free Software Foundation, Inc.
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at assemblers) written by James Hacker.
<signature of Ty Coon>, 1 April 1989
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That's all there is to it!
--- The Artistic License 1.0 ---
This software is Copyright (c) 2012 by Paul Evans <leonerd@leonerd.org.uk>.
This is free software, licensed under:
The Artistic License 1.0
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The End
doc/modules/README.List-UtilsBy
NAME
`List::UtilsBy' - higher-order list utility functions
SYNOPSIS
use List::UtilsBy qw( nsort_by min_by );
use File::stat qw( stat );
my @files_by_age = nsort_by { stat($_)->mtime } @files;
my $shortest_name = min_by { length } @names;
DESCRIPTION
This module provides a number of list utility functions, all of which
take an initial code block to control their behaviour. They are
variations on similar core perl or `List::Util' functions of similar
names, but which use the block to control their behaviour. For example,
the core Perl function `sort' takes a list of values and returns them,
sorted into order by their string value. The `sort_by' function sorts
them according to the string value returned by the extra function, when
given each value.
my @names_sorted = sort @names;
my @people_sorted = sort_by { $_->name } @people;
FUNCTIONS
@vals = sort_by { KEYFUNC } @vals
Returns the list of values sorted according to the string values
returned by the `KEYFUNC' block or function. A typical use of this may
be to sort objects according to the string value of some accessor, such
as
sort_by { $_->name } @people
The key function is called in scalar context, being passed each value in
turn as both `$_' and the only argument in the parameters, `@_'. The
values are then sorted according to string comparisons on the values
returned.
This is equivalent to
sort { $a->name cmp $b->name } @people
except that it guarantees the `name' accessor will be executed only once
per value.
One interesting use-case is to sort strings which may have numbers
embedded in them "naturally", rather than lexically.
sort_by { s/(\d+)/sprintf "%09d", $1/eg; $_ } @strings
This sorts strings by generating sort keys which zero-pad the embedded
numbers to some level (9 digits in this case), helping to ensure the
lexical sort puts them in the correct order.
@vals = nsort_by { KEYFUNC } @vals
Similar to `sort_by' but compares its key values numerically.
@vals = rev_sort_by { KEYFUNC } @vals
@vals = rev_nsort_by { KEYFUNC } @vals
Similar to `sort_by' and `nsort_by' but returns the list in the reverse
order. Equivalent to
@vals = reverse sort_by { KEYFUNC } @vals
except that these functions are slightly more efficient because they
avoid the final `reverse' operation.
$optimal = max_by { KEYFUNC } @vals
@optimal = max_by { KEYFUNC } @vals
Returns the (first) value from `@vals' that gives the numerically
largest result from the key function.
my $tallest = max_by { $_->height } @people
use File::stat qw( stat );
my $newest = max_by { stat($_)->mtime } @files;
In scalar context, the first maximal value is returned. In list context,
a list of all the maximal values is returned. This may be used to obtain
positions other than the first, if order is significant.
If called on an empty list, an empty list is returned.
For symmetry with the `nsort_by' function, this is also provided under
the name `nmax_by' since it behaves numerically.
$optimal = min_by { KEYFUNC } @vals
@optimal = min_by { KEYFUNC } @vals
Similar to `max_by' but returns values which give the numerically
smallest result from the key function. Also provided as `nmin_by'
@vals = uniq_by { KEYFUNC } @vals
Returns a list of the subset of values for which the key function block
returns unique values. The first value yielding a particular key is
chosen, subsequent values are rejected.
my @some_fruit = uniq_by { $_->colour } @fruit;
To select instead the last value per key, reverse the input list. If the
order of the results is significant, don't forget to reverse the result
as well:
my @some_fruit = reverse uniq_by { $_->colour } reverse @fruit;
%parts = partition_by { KEYFUNC } @vals
Returns a key/value list of ARRAY refs containing all the original
values distributed according to the result of the key function block.
Each value will be an ARRAY ref containing all the values which returned
the string from the key function, in their original order.
my %balls_by_colour = partition_by { $_->colour } @balls;
Because the values returned by the key function are used as hash keys,
they ought to either be strings, or at least well-behaved as strings
(such as numbers, or object references which overload stringification in
a suitable manner).
%counts = count_by { KEYFUNC } @vals
Returns a key/value list of integers, giving the number of times the key
function block returned the key, for each value in the list.
my %count_of_balls = count_by { $_->colour } @balls;
Because the values returned by the key function are used as hash keys,
they ought to either be strings, or at least well-behaved as strings
(such as numbers, or object references which overload stringification in
a suitable manner).
@vals = zip_by { ITEMFUNC } \@arr0, \@arr1, \@arr2,...
Returns a list of each of the values returned by the function block,
when invoked with values from across each each of the given ARRAY
references. Each value in the returned list will be the result of the
function having been invoked with arguments at that position, from
across each of the arrays given.
my @transposition = zip_by { [ @_ ] } @matrix;
my @names = zip_by { "$_[1], $_[0]" } \@firstnames, \@surnames;
print zip_by { "$_[0] => $_[1]\n" } [ keys %hash ], [ values %hash ];
If some of the arrays are shorter than others, the function will behave
as if they had `undef' in the trailing positions. The following two
lines are equivalent:
zip_by { f(@_) } [ 1, 2, 3 ], [ "a", "b" ]
f( 1, "a" ), f( 2, "b" ), f( 3, undef )
The item function is called by `map', so if it returns a list, the
entire list is included in the result. This can be useful for example,
for generating a hash from two separate lists of keys and values
my %nums = zip_by { @_ } [qw( one two three )], [ 1, 2, 3 ];
# %nums = ( one => 1, two => 2, three => 3 )
(A function having this behaviour is sometimes called `zipWith', e.g. in
Haskell, but that name would not fit the naming scheme used by this
module).
$arr0, $arr1, $arr2, ... = unzip_by { ITEMFUNC } @vals
Returns a list of ARRAY references containing the values returned by the
function block, when invoked for each of the values given in the input
list. Each of the returned ARRAY references will contain the values
returned at that corresponding position by the function block. That is,
the first returned ARRAY reference will contain all the values returned
in the first position by the function block, the second will contain all
the values from the second position, and so on.
my ( $firstnames, $lastnames ) = unzip_by { m/^(.*?) (.*)$/ } @names;
If the function returns lists of differing lengths, the result will be
padded with `undef' in the missing elements.
This function is an inverse of `zip_by', if given a corresponding
inverse function.
@vals = extract_by { SELECTFUNC } @arr
Removes elements from the referenced array on which the selection
function returns true, and returns a list containing those elements.
This function is similar to `grep', except that it modifies the
referenced array to remove the selected values from it, leaving only the
unselected ones.
my @red_balls = extract_by { $_->color eq "red" } @balls;
# Now there are no red balls in the @balls array
This function modifies a real array, unlike most of the other functions
in this module. Because of this, it requires a real array, not just a
list.
This function is implemented by invoking `splice()' on the array, not by
constructing a new list and assigning it. One result of this is that
weak references will not be disturbed.
extract_by { !defined $_ } @refs;
will leave weak references weakened in the `@refs' array, whereas
@refs = grep { defined $_ } @refs;
will strengthen them all again.
@vals = weighted_shuffle_by { WEIGHTFUNC } @vals
Returns the list of values shuffled into a random order. The
randomisation is not uniform, but weighted by the value returned by the
`WEIGHTFUNC'. The probabilty of each item being returned first will be
distributed with the distribution of the weights, and so on recursively
for the remaining items.
@vals = bundle_by { BLOCKFUNC } $number, @vals
Similar to a regular `map' functional, returns a list of the values
returned by `BLOCKFUNC'. Values from the input list are given to the
block function in bundles of `$number'.
If given a list of values whose length does not evenly divide by
`$number', the final call will be passed fewer elements than the others.
TODO
* XS implementations
These functions are currently all written in pure perl. Some at
least, may benefit from having XS implementations to speed up their
logic.
* Merge into List::Util or List::MoreUtils
This module shouldn't really exist. The functions should instead be
part of one of the existing modules that already contain many list
utility functions. Having Yet Another List Utilty Module just
worsens the problem.
I have attempted to contact the authors of both of the above
modules, to no avail; therefore I decided it best to write and
release this code here anyway so that it is at least on CPAN. Once
there, we can then see how best to merge it into an existing module.
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
modules/fallback/List/UtilsBy.pm
# You may distribute under the terms of either the GNU General Public License
# or the Artistic License (the same terms as Perl itself)
#
# (C) Paul Evans, 2009-2012 -- leonerd@leonerd.org.uk
package List::UtilsBy;
use strict;
use warnings;
our $VERSION = '0.09';
use Exporter 'import';
our @EXPORT_OK = qw(
sort_by
nsort_by
rev_sort_by
rev_nsort_by
max_by nmax_by
min_by nmin_by
uniq_by
partition_by
count_by
zip_by
unzip_by
extract_by
weighted_shuffle_by
bundle_by
);
=head1 NAME
C<List::UtilsBy> - higher-order list utility functions
=head1 SYNOPSIS
use List::UtilsBy qw( nsort_by min_by );
use File::stat qw( stat );
my @files_by_age = nsort_by { stat($_)->mtime } @files;
my $shortest_name = min_by { length } @names;
=head1 DESCRIPTION
This module provides a number of list utility functions, all of which take an
initial code block to control their behaviour. They are variations on similar
core perl or C<List::Util> functions of similar names, but which use the block
to control their behaviour. For example, the core Perl function C<sort> takes
a list of values and returns them, sorted into order by their string value.
The C<sort_by> function sorts them according to the string value returned by
the extra function, when given each value.
my @names_sorted = sort @names;
my @people_sorted = sort_by { $_->name } @people;
=cut
=head1 FUNCTIONS
=cut
=head2 @vals = sort_by { KEYFUNC } @vals
Returns the list of values sorted according to the string values returned by
the C<KEYFUNC> block or function. A typical use of this may be to sort objects
according to the string value of some accessor, such as
sort_by { $_->name } @people
The key function is called in scalar context, being passed each value in turn
as both C<$_> and the only argument in the parameters, C<@_>. The values are
then sorted according to string comparisons on the values returned.
This is equivalent to
sort { $a->name cmp $b->name } @people
except that it guarantees the C<name> accessor will be executed only once per
value.
One interesting use-case is to sort strings which may have numbers embedded in
them "naturally", rather than lexically.
sort_by { s/(\d+)/sprintf "%09d", $1/eg; $_ } @strings
This sorts strings by generating sort keys which zero-pad the embedded numbers
to some level (9 digits in this case), helping to ensure the lexical sort puts
them in the correct order.
=cut
sub sort_by(&@)
{
my $keygen = shift;
my @keys = map { local $_ = $_; scalar $keygen->( $_ ) } @_;
return @_[ sort { $keys[$a] cmp $keys[$b] } 0 .. $#_ ];
}
=head2 @vals = nsort_by { KEYFUNC } @vals
Similar to C<sort_by> but compares its key values numerically.
=cut
sub nsort_by(&@)
{
my $keygen = shift;
my @keys = map { local $_ = $_; scalar $keygen->( $_ ) } @_;
return @_[ sort { $keys[$a] <=> $keys[$b] } 0 .. $#_ ];
}
=head2 @vals = rev_sort_by { KEYFUNC } @vals
=head2 @vals = rev_nsort_by { KEYFUNC } @vals
Similar to C<sort_by> and C<nsort_by> but returns the list in the reverse
order. Equivalent to
@vals = reverse sort_by { KEYFUNC } @vals
except that these functions are slightly more efficient because they avoid
the final C<reverse> operation.
=cut
sub rev_sort_by(&@)
{
my $keygen = shift;
my @keys = map { local $_ = $_; scalar $keygen->( $_ ) } @_;
return @_[ sort { $keys[$b] cmp $keys[$a] } 0 .. $#_ ];
}
sub rev_nsort_by(&@)
{
my $keygen = shift;
my @keys = map { local $_ = $_; scalar $keygen->( $_ ) } @_;
return @_[ sort { $keys[$b] <=> $keys[$a] } 0 .. $#_ ];
}
=head2 $optimal = max_by { KEYFUNC } @vals
=head2 @optimal = max_by { KEYFUNC } @vals
Returns the (first) value from C<@vals> that gives the numerically largest
result from the key function.
my $tallest = max_by { $_->height } @people
use File::stat qw( stat );
my $newest = max_by { stat($_)->mtime } @files;
In scalar context, the first maximal value is returned. In list context, a
list of all the maximal values is returned. This may be used to obtain
positions other than the first, if order is significant.
If called on an empty list, an empty list is returned.
For symmetry with the C<nsort_by> function, this is also provided under the
name C<nmax_by> since it behaves numerically.
=cut
sub max_by(&@)
{
my $code = shift;
return unless @_;
local $_;
my @maximal = $_ = shift @_;
my $max = $code->( $_ );
foreach ( @_ ) {
my $this = $code->( $_ );
if( $this > $max ) {
@maximal = $_;
$max = $this;
}
elsif( wantarray and $this == $max ) {
push @maximal, $_;
}
}
return wantarray ? @maximal : $maximal[0];
}
*nmax_by = \&max_by;
=head2 $optimal = min_by { KEYFUNC } @vals
=head2 @optimal = min_by { KEYFUNC } @vals
Similar to C<max_by> but returns values which give the numerically smallest
result from the key function. Also provided as C<nmin_by>
=cut
sub min_by(&@)
{
my $code = shift;
return unless @_;
local $_;
my @minimal = $_ = shift @_;
my $min = $code->( $_ );
foreach ( @_ ) {
my $this = $code->( $_ );
if( $this < $min ) {
@minimal = $_;
$min = $this;
}
elsif( wantarray and $this == $min ) {
push @minimal, $_;
}
}
return wantarray ? @minimal : $minimal[0];
}
*nmin_by = \&min_by;
=head2 @vals = uniq_by { KEYFUNC } @vals
Returns a list of the subset of values for which the key function block
returns unique values. The first value yielding a particular key is chosen,
subsequent values are rejected.
my @some_fruit = uniq_by { $_->colour } @fruit;
To select instead the last value per key, reverse the input list. If the order
of the results is significant, don't forget to reverse the result as well:
my @some_fruit = reverse uniq_by { $_->colour } reverse @fruit;
=cut
sub uniq_by(&@)
{
my $code = shift;
my %present;
return grep {
my $key = $code->( local $_ = $_ );
!$present{$key}++
} @_;
}
=head2 %parts = partition_by { KEYFUNC } @vals
Returns a key/value list of ARRAY refs containing all the original values
distributed according to the result of the key function block. Each value will
be an ARRAY ref containing all the values which returned the string from the
key function, in their original order.
my %balls_by_colour = partition_by { $_->colour } @balls;
Because the values returned by the key function are used as hash keys, they
ought to either be strings, or at least well-behaved as strings (such as
numbers, or object references which overload stringification in a suitable
manner).
=cut
sub partition_by(&@)
{
my $code = shift;
my %parts;
push @{ $parts{ $code->( local $_ = $_ ) } }, $_ for @_;
return %parts;
}
=head2 %counts = count_by { KEYFUNC } @vals
Returns a key/value list of integers, giving the number of times the key
function block returned the key, for each value in the list.
my %count_of_balls = count_by { $_->colour } @balls;
Because the values returned by the key function are used as hash keys, they
ought to either be strings, or at least well-behaved as strings (such as
numbers, or object references which overload stringification in a suitable
manner).
=cut
sub count_by(&@)
{
my $code = shift;
my %counts;
$counts{ $code->( local $_ = $_ ) }++ for @_;
return %counts;
}
=head2 @vals = zip_by { ITEMFUNC } \@arr0, \@arr1, \@arr2,...
Returns a list of each of the values returned by the function block, when
invoked with values from across each each of the given ARRAY references. Each
value in the returned list will be the result of the function having been
invoked with arguments at that position, from across each of the arrays given.
my @transposition = zip_by { [ @_ ] } @matrix;
my @names = zip_by { "$_[1], $_[0]" } \@firstnames, \@surnames;
print zip_by { "$_[0] => $_[1]\n" } [ keys %hash ], [ values %hash ];
If some of the arrays are shorter than others, the function will behave as if
they had C<undef> in the trailing positions. The following two lines are
equivalent:
zip_by { f(@_) } [ 1, 2, 3 ], [ "a", "b" ]
f( 1, "a" ), f( 2, "b" ), f( 3, undef )
The item function is called by C<map>, so if it returns a list, the entire
list is included in the result. This can be useful for example, for generating
a hash from two separate lists of keys and values
my %nums = zip_by { @_ } [qw( one two three )], [ 1, 2, 3 ];
# %nums = ( one => 1, two => 2, three => 3 )
(A function having this behaviour is sometimes called C<zipWith>, e.g. in
Haskell, but that name would not fit the naming scheme used by this module).
=cut
sub zip_by(&@)
{
my $code = shift;
@_ or return;
my $len = 0;
scalar @$_ > $len and $len = scalar @$_ for @_;
return map {
my $idx = $_;
$code->( map { $_[$_][$idx] } 0 .. $#_ )
} 0 .. $len-1;
}
=head2 $arr0, $arr1, $arr2, ... = unzip_by { ITEMFUNC } @vals
Returns a list of ARRAY references containing the values returned by the
function block, when invoked for each of the values given in the input list.
Each of the returned ARRAY references will contain the values returned at that
corresponding position by the function block. That is, the first returned
ARRAY reference will contain all the values returned in the first position by
the function block, the second will contain all the values from the second
position, and so on.
my ( $firstnames, $lastnames ) = unzip_by { m/^(.*?) (.*)$/ } @names;
If the function returns lists of differing lengths, the result will be padded
with C<undef> in the missing elements.
This function is an inverse of C<zip_by>, if given a corresponding inverse
function.
=cut
sub unzip_by(&@)
{
my $code = shift;
my @ret;
foreach my $idx ( 0 .. $#_ ) {
my @slice = $code->( local $_ = $_[$idx] );
$#slice = $#ret if @slice < @ret;
$ret[$_][$idx] = $slice[$_] for 0 .. $#slice;
}
return @ret;
}
=head2 @vals = extract_by { SELECTFUNC } @arr
Removes elements from the referenced array on which the selection function
returns true, and returns a list containing those elements. This function is
similar to C<grep>, except that it modifies the referenced array to remove the
selected values from it, leaving only the unselected ones.
my @red_balls = extract_by { $_->color eq "red" } @balls;
# Now there are no red balls in the @balls array
This function modifies a real array, unlike most of the other functions in this
module. Because of this, it requires a real array, not just a list.
This function is implemented by invoking C<splice()> on the array, not by
constructing a new list and assigning it. One result of this is that weak
references will not be disturbed.
extract_by { !defined $_ } @refs;
will leave weak references weakened in the C<@refs> array, whereas
@refs = grep { defined $_ } @refs;
will strengthen them all again.
=cut
sub extract_by(&\@)
{
my $code = shift;
my ( $arrref ) = @_;
my @ret;
for( my $idx = 0; $idx < scalar @$arrref; ) {
if( $code->( local $_ = $arrref->[$idx] ) ) {
push @ret, splice @$arrref, $idx, 1, ();
}
else {
$idx++;
}
}
return @ret;
}
=head2 @vals = weighted_shuffle_by { WEIGHTFUNC } @vals
Returns the list of values shuffled into a random order. The randomisation is
not uniform, but weighted by the value returned by the C<WEIGHTFUNC>. The
probabilty of each item being returned first will be distributed with the
distribution of the weights, and so on recursively for the remaining items.
=cut
sub weighted_shuffle_by(&@)
{
my $code = shift;
my @vals = @_;
my @weights = map { $code->( local $_ = $_ ) } @vals;
my @ret;
while( @vals > 1 ) {
my $total = 0; $total += $_ for @weights;
my $select = int rand $total;
my $idx = 0;
while( $select >= $weights[$idx] ) {
$select -= $weights[$idx++];
}
push @ret, splice @vals, $idx, 1, ();
splice @weights, $idx, 1, ();
}
push @ret, @vals if @vals;
return @ret;
}
=head2 @vals = bundle_by { BLOCKFUNC } $number, @vals
Similar to a regular C<map> functional, returns a list of the values returned
by C<BLOCKFUNC>. Values from the input list are given to the block function in
bundles of C<$number>.
If given a list of values whose length does not evenly divide by C<$number>,
the final call will be passed fewer elements than the others.
=cut
sub bundle_by(&@)
{
my $code = shift;
my $n = shift;
my @ret;
for( my ( $pos, $next ) = ( 0, $n ); $pos < @_; $pos = $next, $next += $n ) {
$next = @_ if $next > @_;
push @ret, $code->( @_[$pos .. $next-1] );
}
return @ret;
}
=head1 TODO
=over 4
=item * XS implementations
These functions are currently all written in pure perl. Some at least, may
benefit from having XS implementations to speed up their logic.
=item * Merge into L<List::Util> or L<List::MoreUtils>
This module shouldn't really exist. The functions should instead be part of
one of the existing modules that already contain many list utility functions.
Having Yet Another List Utilty Module just worsens the problem.
I have attempted to contact the authors of both of the above modules, to no
avail; therefore I decided it best to write and release this code here anyway
so that it is at least on CPAN. Once there, we can then see how best to merge
it into an existing module.
=back
=head1 AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
=cut
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