NAME¶
List::AllUtils - Combines List::Util and List::MoreUtils in one bite-sized
package
VERSION¶
version 0.09
SYNOPSIS¶
use List::AllUtils qw( first any );
# _Everything_ from List::Util and List::MoreUtils
use List::AllUtils qw( :all );
my @numbers = ( 1, 2, 3, 5, 7 );
# 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.
Note that all function documentation has been shamelessly copied from List::Util
and List::MoreUtils.
Which One Wins?¶
Recently, List::Util has started including some of the subs that used to only be
in List::MoreUtils. This module always exports the version provided by
List::Util.
The docs below come from List::Util 1.31 and List::MoreUtils 0.28.
LIST-REDUCTION FUNCTIONS¶
The following set of functions all reduce a list down to a single value.
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
If your algorithm requires that "reduce" produce an identity value,
then make sure that you always pass that identity value as the first argument
to prevent "undef" being returned
$foo = reduce { $a + $b } 0, @values; # sum with 0 identity value
The remaining list-reduction functions are all specialisations of this generic
idea.
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
$foo = reduce { defined($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'
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
sum0 LIST¶
Similar to "sum", except this returns 0 when given an empty list,
rather than "undef".
KEY/VALUE PAIR LIST FUNCTIONS¶
The following set of functions, all inspired by List::Pairwise, consume an
even-sized list of pairs. The pairs may be key/value associations from a hash,
or just a list of values. The functions will all preserve the original
ordering of the pairs, and will not be confused by multiple pairs having the
same "key" value - nor even do they require that the first of each
pair be a plain string.
pairgrep BLOCK KVLIST¶
Similar to perl's "grep" keyword, but interprets the given list as an
even-sized list of pairs. It invokes the BLOCK multiple times, in scalar
context, with $a and $b set to successive pairs of values from the KVLIST.
Returns an even-sized list of those pairs for which the BLOCK returned true in
list context, or the count of the
number of pairs in scalar context.
(Note, therefore, in scalar context that it returns a number half the size of
the count of items it would have returned in list context).
@subset = pairgrep { $a =~ m/^[[:upper:]]+$/ } @kvlist
Similar to "grep", "pairgrep" aliases $a and $b to elements
of the given list. Any modifications of it by the code block will be visible
to the caller.
pairfirst BLOCK KVLIST¶
Similar to the "first" function, but interprets the given list as an
even-sized list of pairs. It invokes the BLOCK multiple times, in scalar
context, with $a and $b set to successive pairs of values from the KVLIST.
Returns the first pair of values from the list for which the BLOCK returned true
in list context, or an empty list of no such pair was found. In scalar context
it returns a simple boolean value, rather than either the key or the value
found.
( $key, $value ) = pairfirst { $a =~ m/^[[:upper:]]+$/ } @kvlist
Similar to "grep", "pairfirst" aliases $a and $b to elements
of the given list. Any modifications of it by the code block will be visible
to the caller.
pairmap BLOCK KVLIST¶
Similar to perl's "map" keyword, but interprets the given list as an
even-sized list of pairs. It invokes the BLOCK multiple times, in list
context, with $a and $b set to successive pairs of values from the KVLIST.
Returns the concatenation of all the values returned by the BLOCK in list
context, or the count of the number of items that would have been returned in
scalar context.
@result = pairmap { "The key $a has value $b" } @kvlist
Similar to "map", "pairmap" aliases $a and $b to elements of
the given list. Any modifications of it by the code block will be visible to
the caller.
pairs KVLIST¶
A convenient shortcut to operating on even-sized lists of pairs, this function
returns a list of ARRAY references, each containing two items from the given
list. It is a more efficient version of
pairmap { [ $a, $b ] } KVLIST
It is most convenient to use in a "foreach" loop, for example:
foreach ( pairs @KVLIST ) {
my ( $key, $value ) = @$_;
...
}
pairkeys KVLIST¶
A convenient shortcut to operating on even-sized lists of pairs, this function
returns a list of the the first values of each of the pairs in the given list.
It is a more efficient version of
pairmap { $a } KVLIST
pairvalues KVLIST¶
A convenient shortcut to operating on even-sized lists of pairs, this function
returns a list of the the second values of each of the pairs in the given
list. It is a more efficient version of
pairmap { $b } KVLIST
OTHER FUNCTIONS¶
shuffle LIST¶
Returns the elements of LIST in a random order
@cards = shuffle 0..51 # 0..51 in a random order
List::MoreUtils FUNCTIONS¶
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 if LIST is empty.
all BLOCK LIST¶
Returns a true value if all items in LIST meet the criterion given through
BLOCK, or if LIST is empty. Sets $_ for each item in LIST in turn:
print "All items defined"
if all { defined($_) } @list;
Returns false otherwise.
none BLOCK LIST¶
Logically the negation of "any". Returns a true value if no item in
LIST meets the criterion given through BLOCK, or if LIST is empty. Sets $_ for
each item in LIST in turn:
print "No value defined"
if none { defined($_) } @list;
Returns false otherwise.
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 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 }
before BLOCK LIST¶
Returns a list of values of LIST up to (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.
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 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 returns
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 EXPR, 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¶
distinct 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 okay 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.
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.
AUTHOR¶
Dave Rolsky <autarch@urth.org>
COPYRIGHT AND LICENSE¶
This software is Copyright (c) 2014 by Dave Rolsky.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)