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NAME

List::Util - A selection of general-utility list subroutines
 

SYNOPSIS

    use List::Util qw(first max maxstr min minstr reduce shuffle sum);

DESCRIPTION

By default "List::Util" does not export any subroutines. The subroutines defined are

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'

reduce BLOCK LIST

Reduces LIST by calling BLOCK 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

KNOWN BUGS

SUGGESTED ADDITIONS

  # One argument is true

  sub any { $_ && return 1 for @_; 0 }

  # All arguments are true

  sub all { $_ || return 0 for @_; 1 }

  # All arguments are false

  sub none { $_ && return 0 for @_; 1 }

  # One argument is false

  sub notall { $_ || return 1 for @_; 0 }

  # How many elements are true

  sub true { scalar grep { $_ } @_ }

  # How many elements are false

  sub false { scalar grep { !$_ } @_ }

COPYRIGHT

Index

NAME

SYNOPSIS

DESCRIPTION

KNOWN BUGS

SUGGESTED ADDITIONS

COPYRIGHT

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