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Top Forums Web Development Intersection and union of array by hash Post 302500409 by yifangt on Monday 28th of February 2011 01:18:12 PM
Old 02-28-2011
Intersection and union of array by hash

Hi,

A piece of script from Perl-cookbook I do not understand, and post here for explanation.
The purpose is to find the element in either array (union), and in both array (intersection). Thank you in advance.

Code:
@a=qw(1 3 5 6 7 8);
@b=qw(2 3 5 7 9);

foreach $e (@a, @b) {$union{$e}++ && $isect{$e}++}

@union = keys %union;
@isect = keys %isect;

How is the third line:
Code:
foreach $e (@a, @b) {$union{$e}++ && $isect{$e}++}

working behind? I am desperate to understand it.
 

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RESET(3)								 1								  RESET(3)

reset - Set the internal pointer of an array to its first element

SYNOPSIS
mixed reset (array &$array) DESCRIPTION
reset(3) rewinds $array's internal pointer to the first element and returns the value of the first array element. PARAMETERS
o $array - The input array. RETURN VALUES
Returns the value of the first array element, or FALSE if the array is empty. EXAMPLES
Example #1 reset(3) example <?php $array = array('step one', 'step two', 'step three', 'step four'); // by default, the pointer is on the first element echo current($array) . "<br /> "; // "step one" // skip two steps next($array); next($array); echo current($array) . "<br /> "; // "step three" // reset pointer, start again on step one reset($array); echo current($array) . "<br /> "; // "step one" ?> SEE ALSO
current(3), each(3), end(3), next(3), prev(3). PHP Documentation Group RESET(3)
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