NAME
List::AllUtils - Combines List::Util and List::MoreUtils in one
bite-sized package
SYNOPSIS
use List::AllUtils qw( first any );
# _Everything_ from List::Util and List::MoreUtils
use List::AllUtils qw( :all );
# or don't import anything
return List::AllUtils::first { $_ > 5 } @numbers;
DESCRIPTION
Are you sick of trying to remember whether a particular helper is
defined in `List::Util' or `List::MoreUtils'? I sure am. Now you don't
have to remember. This module will export all of the functions that
either of those two modules defines.
FUNCTIONS
(Shamelessly copied from List::Util and List::MoreUtils ...)
first BLOCK LIST
Similar to `grep' in that it evaluates BLOCK setting `$_' to each
element of LIST in turn. `first' returns the first element where the
result from BLOCK is a true value. If BLOCK never returns true or LIST
was empty then `undef' is returned.
$foo = first { defined($_) } @list # first defined value in @list
$foo = first { $_ > $value } @list # first value in @list which
# is greater than $value
This function could be implemented using `reduce' like this
$foo = reduce { wanted($a) ? $a : wanted($b) ? $b : undef } undef, @list
for example wanted() could be defined() which would return the first
defined value in @list
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 { $a > $b ? $a : $b } 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 { $a gt $b ? $a : $b } '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 { $a < $b ? $a : $b } 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 = minstr 'A'..'Z' # 'A'
$foo = minstr "hello","world" # "hello"
$foo = minstr @bar, @baz # whatever
This function could be implemented using `reduce' like this
$foo = reduce { $a lt $b ? $a : $b } 'A'..'Z'
reduce BLOCK LIST
Reduces LIST by calling BLOCK, in a scalar context, multiple times,
setting `$a' and `$b' each time. The first call will be with `$a' and
`$b' set to the first two elements of the list, subsequent calls will be
done by setting `$a' to the result of the previous call and `$b' to 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 { $a < $b ? $a : $b } 1..10 # min
$foo = reduce { $a lt $b ? $a : $b } 'aa'..'zz' # minstr
$foo = reduce { $a + $b } 1 .. 10 # sum
$foo = reduce { $a . $b } @bar # concat
shuffle LIST
Returns the elements of LIST in a random order
@cards = shuffle 0..51 # 0..51 in a random order
sum LIST
Returns the sum of all the elements in LIST. If LIST is empty then
`undef' is returned.
$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 { $a + $b } 1..10
any BLOCK LIST
Returns a true value if any item in LIST meets the criterion given
through BLOCK. Sets `$_' for each item in LIST in turn:
print "At least one value undefined"
if any { !defined($_) } @list;
Returns false otherwise, or `undef' if LIST is empty.
all BLOCK LIST
Returns a true value if all items in LIST meet the criterion given
through BLOCK. Sets `$_' for each item in LIST in turn:
print "All items defined"
if all { defined($_) } @list;
Returns false otherwise, or `undef' if LIST is empty.
none BLOCK LIST
Logically the negation of `any'. Returns a true value if no item in LIST
meets the criterion given through BLOCK. Sets `$_' for each item in LIST
in turn:
print "No value defined"
if none { defined($_) } @list;
Returns false otherwise, or `undef' if LIST is empty.
notall BLOCK LIST
Logically the negation of `all'. Returns a true value if not all items
in LIST meet the criterion given through BLOCK. Sets `$_' for each item
in LIST in turn:
print "Not all values defined"
if notall { defined($_) } @list;
Returns false otherwise, or `undef' if LIST is empty.
true BLOCK LIST
Counts the number of elements in LIST for which the criterion in BLOCK
is true. Sets `$_' for each item in LIST in turn:
printf "%i item(s) are defined", true { defined($_) } @list;
false BLOCK LIST
Counts the number of elements in LIST for which the criterion in BLOCK
is false. Sets `$_' for each item in LIST in turn:
printf "%i item(s) are not defined", false { defined($_) } @list;
firstidx BLOCK LIST
first_index BLOCK LIST
Returns the index of the first element in LIST for which the criterion
in BLOCK is true. Sets `$_' for each item in LIST in turn:
my @list = (1, 4, 3, 2, 4, 6);
printf "item with index %i in list is 4", firstidx { $_ == 4 } @list;
__END__
item with index 1 in list is 4
Returns `-1' if no such item could be found.
`first_index' is an alias for `firstidx'.
lastidx BLOCK LIST
last_index BLOCK LIST
Returns the index of the last element in LIST for which the criterion in
BLOCK is true. Sets `$_' for each item in LIST in turn:
my @list = (1, 4, 3, 2, 4, 6);
printf "item with index %i in list is 4", lastidx { $_ == 4 } @list;
__END__
item with index 4 in list is 4
Returns `-1' if no such item could be found.
`last_index' is an alias for `lastidx'.
insert_after BLOCK VALUE LIST
Inserts VALUE after the first item in LIST for which the criterion in
BLOCK is true. Sets `$_' for each item in LIST in turn.
my @list = qw/This is a list/;
insert_after { $_ eq "a" } "longer" => @list;
print "@list";
__END__
This is a longer list
insert_after_string STRING VALUE LIST
Inserts VALUE after the first item in LIST which is equal to STRING.
my @list = qw/This is a list/;
insert_after_string "a", "longer" => @list;
print "@list";
__END__
This is a longer list
apply BLOCK LIST
Applies BLOCK to each item in LIST and returns a list of the values
after BLOCK has been applied. In scalar context, the last element is
returned. This function is similar to `map' but will not modify the
elements of the input list:
my @list = (1 .. 4);
my @mult = apply { $_ *= 2 } @list;
print "\@list = @list\n";
print "\@mult = @mult\n";
__END__
@list = 1 2 3 4
@mult = 2 4 6 8
Think of it as syntactic sugar for
for (my @mult = @list) { $_ *= 2 }
after BLOCK LIST
Returns a list of the values of LIST after (and not including) the point
where BLOCK returns a true value. Sets `$_' for each element in LIST in
turn.
@x = after { $_ % 5 == 0 } (1..9); # returns 6, 7, 8, 9
after_incl BLOCK LIST
Same as `after' but also inclues the element for which BLOCK is true.
before BLOCK LIST
Returns a list of values of LIST upto (and not including) the point
where BLOCK returns a true value. Sets `$_' for each element in LIST in
turn.
before_incl BLOCK LIST
Same as `before' but also includes the element for which BLOCK is true.
indexes BLOCK LIST
Evaluates BLOCK for each element in LIST (assigned to `$_') and returns
a list of the indices of those elements for which BLOCK returned a true
value. This is just like `grep' only that it returns indices instead of
values:
@x = indexes { $_ % 2 == 0 } (1..10); # returns 1, 3, 5, 7, 9
firstval BLOCK LIST
first_value BLOCK LIST
Returns the first element in LIST for which BLOCK evaluates to true.
Each element of LIST is set to `$_' in turn. Returns `undef' if no such
element has been found.
`first_val' is an alias for `firstval'.
lastval BLOCK LIST
last_value BLOCK LIST
Returns the last value in LIST for which BLOCK evaluates to true. Each
element of LIST is set to `$_' in turn. Returns `undef' if no such
element has been found.
`last_val' is an alias for `lastval'.
pairwise BLOCK ARRAY1 ARRAY2
Evaluates BLOCK for each pair of elements in ARRAY1 and ARRAY2 and
returns a new list consisting of BLOCK's return values. The two elements
are set to `$a' and `$b'. Note that those two are aliases to the
original value so changing them will modify the input arrays.
@a = (1 .. 5);
@b = (11 .. 15);
@x = pairwise { $a + $b } @a, @b; # returns 12, 14, 16, 18, 20
# mesh with pairwise
@a = qw/a b c/;
@b = qw/1 2 3/;
@x = pairwise { ($a, $b) } @a, @b; # returns a, 1, b, 2, c, 3
each_array ARRAY1 ARRAY2 ...
Creates an array iterator to return the elements of the list of arrays
ARRAY1, ARRAY2 throughout ARRAYn in turn. That is, the first time it is
called, it returns the first element of each array. The next time, it
returns the second elements. And so on, until all elements are
exhausted.
This is useful for looping over more than one array at once:
my $ea = each_array(@a, @b, @c);
while ( my ($a, $b, $c) = $ea->() ) { .... }
The iterator returns the empty list when it reached the end of all
arrays.
If the iterator is passed an argument of '`index'', then it retuns the
index of the last fetched set of values, as a scalar.
each_arrayref LIST
Like each_array, but the arguments are references to arrays, not the
plain arrays.
natatime BLOCK LIST
Creates an array iterator, for looping over an array in chunks of `$n'
items at a time. (n at a time, get it?). An example is probably a better
explanation than I could give in words.
Example:
my @x = ('a' .. 'g');
my $it = natatime 3, @x;
while (my @vals = $it->())
{
print "@vals\n";
}
This prints
a b c
d e f
g
mesh ARRAY1 ARRAY2 [ ARRAY3 ... ]
zip ARRAY1 ARRAY2 [ ARRAY3 ... ]
Returns a list consisting of the first elements of each array, then the
second, then the third, etc, until all arrays are exhausted.
Examples:
@x = qw/a b c d/;
@y = qw/1 2 3 4/;
@z = mesh @x, @y; # returns a, 1, b, 2, c, 3, d, 4
@a = ('x');
@b = ('1', '2');
@c = qw/zip zap zot/;
@d = mesh @a, @b, @c; # x, 1, zip, undef, 2, zap, undef, undef, zot
`zip' is an alias for `mesh'.
uniq LIST
Returns a new list by stripping duplicate values in LIST. The order of
elements in the returned list is the same as in LIST. In scalar context,
returns the number of unique elements in LIST.
my @x = uniq 1, 1, 2, 2, 3, 5, 3, 4; # returns 1 2 3 5 4
my $x = uniq 1, 1, 2, 2, 3, 5, 3, 4; # returns 5
minmax LIST
Calculates the minimum and maximum of LIST and returns a two element
list with the first element being the minimum and the second the
maximum. Returns the empty list if LIST was empty.
The minmax algorithm differs from a naive iteration over the list where
each element is compared to two values being the so far calculated min
and max value in that it only requires 3n/2 - 2 comparisons. Thus it is
the most efficient possible algorithm.
However, the Perl implementation of it has some overhead simply due to
the fact that there are more lines of Perl code involved. Therefore,
LIST needs to be fairly big in order for minmax to win over a naive
implementation. This limitation does not apply to the XS version.
part BLOCK LIST
Partitions LIST based on the return value of BLOCK which denotes into
which partition the current value is put.
Returns a list of the partitions thusly created. Each partition created
is a reference to an array.
my $i = 0;
my @part = part { $i++ % 2 } 1 .. 8; # returns [1, 3, 5, 7], [2, 4, 6, 8]
You can have a sparse list of partitions as well where non-set
partitions will be undef:
my @part = part { 2 } 1 .. 10; # returns undef, undef, [ 1 .. 10 ]
Be careful with negative values, though:
my @part = part { -1 } 1 .. 10;
__END__
Modification of non-creatable array value attempted, subscript -1 ...
Negative values are only ok when they refer to a partition previously
created:
my @idx = (0, 1, -1);
my $i = 0;
my @part = part { $idx[$++ % 3] } 1 .. 8; # [1, 4, 7], [2, 3, 5, 6, 8]
EXPORTS
This module exports nothing by default. You can import functions by
name, or get everything with the `:all' tag.
SEE ALSO
`List::Util' and `List::MoreUtils', obviously.
Also see `Util::Any', which unifies many more util modules, and also
lets you rename functions as part of the import.
AUTHOR
Dave Rolsky, `<autarch@urth.org>'
But really, this module does very little, and all the docs come from
List::Util by Graham Barr and List::MoreUtils by Tassilo von Parseval.
BUGS
Please report any bugs or feature requests to
`bug-list-allutils@rt.cpan.org', or through the web interface at
http://rt.cpan.org. I will be notified, and then you'll automatically be
notified of progress on your bug as I make changes.
COPYRIGHT & LICENSE
Copyright 2009 Dave Rolsky, All Rights Reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.