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Difference between revisions of "String Filter For Character Set"

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Revision as of 08:03, 22 November 2006

Problem

You want to remove all but a specified set of characters from a string.

Solution

This is really a extension of what we talked about in StringCheckForChar. The Erlang lists module provides several functions that allow manipulations of strings (since they are simply lists of characters). For example, to remove non-letters from a string, we could define a predicate that recognizes only letters:

1> lists:filter(fun(X) -> lists:member(X, 
1>     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") end,
1>     "Hello, World!").
"HelloWorld"
37> lists:filter(fun(X) -> not lists:member(X,
37> "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") end,
37> "Hello, World!").
", !"