� # -*- 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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