© # -*- coding: utf-8 -*- © # Python © © # the "filter" function can be used to © # reduce a list such that unwanted © # elements are removed. © # example: © © def even(n): return n % 2 == 0 © print filter( even, range(11)) © © © # the "map" function applies a function © # to all elements of a list. Example: © © def square(n): return n*n © print map(square, range(11)) © © ------------------------------------ © # similar perl versions © © use Data::Dumper; © sub even {return $_[0]%2==0}; © print Dumper[ grep {even $_} (0..10)]; © © © # sub square {$n=shift;$n**2;}; © sub square {(shift)**2;}; © print Dumper [ map {square($_)} (0..10)]; © © # the codes above showcase some syntax © # variations commonly found in perl code © # base © © ------------------------- © © # in Mathematica for example, filter is © # akin to Apply and map is MapThread. © # The standard Map can be applied © # according to a level spec of trees © # and there's also MapAt, Nest, © # NestList...any many more powerful © # functions that manipulates trees. © # lisp languages often have a subset © # of it. © © ---------------------------- © Note: this post is from the Perl-Python © a-day mailing list at © http://groups.yahoo.com/group/perl-python/ © to subscribe, send an email to © [EMAIL PROTECTED] if © you are reading it on a web page, © program examples may not run because © html conversion often breaks the code. © © Xah © [EMAIL PROTECTED] © http://xahlee.org/PageTwo_dir/more.html
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