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map, grep and $_ save loops
Topicalization and Special Variables example from a Well House Consultants training course
More on Topicalization and Special Variables [link]
Source code: exact Module: P210
=head1 Map and Grep save loops Perl's map and grep functions allow you to process every member of a list. With grep, you're performing a test on each list member and producting a new list which contains only those members for which the test is true. Although the usual use of grep is with a regular expression, in fact it can handle any logical test ... each of the items of the incoming list is placed, in turn, in $_ and the test performed. Map also places each element in turn in $_, but rather than returning a shorted list of elements which are identical to elements in the original list, it returns a list of all elements, but transformed through the mapping given. In this example, we use "grep" to see which companies on our industrial estate have an exact multiple of 11 members of staff (perhaps we're making up cricket teams), and we use "map" to get a count of the number of teams for every company. =cut @staff = (4000, 2500, 44, 121, 144, 161); @teams = grep (($_ % 11 == 0), @staff); print "exacts ... @teams\n"; @ntms = map(int($_/11),@staff); print "number of teams ... @ntms\n"; __END__ Sample output: Dorothy:ppcsrd08 grahamellis$ perl exact exacts ... 44 121 number of teams ... 363 227 4 11 13 14 Dorothy:ppcsrd08 grahamellis$ Learn about this subject
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