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From: Jacob Sparre Andersen <sparre@nbi.dk>
Newsgroups: comp.lang.ada
Subject: Re: String filtering
Date: Tue, 27 Sep 2005 09:38:40 +0200
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Date: 2005-09-27T09:38:40+02:00
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David Trudgett wrote:

> I've been puzzling for a little bit over a good way to filter out
> unwanted characters from a string. In particular, I have an
> unbounded string and want to filter out of it all characters not in
> 'a'..'z', 'A'..'Z', '0'..'9'. So far I've only thought of tedious
> ways to do it. Is there an easy way to do it using the string
> handling facilities in Ada? I think I almost got there with the idea
> of using Maps.Character_Set, and so on, but I haven't quite pieced
> it together yet.

I would probably simply iterate over the elements in the string and
copy those which a call to "function Is_In (Element : in Character;
Set : in Character_Set) return Boolean;" indicate to the target
string.

You could use "function Count (Source : in Unbounded_String; Set : in
Maps.Character_Set) return Natural;" to preallocate the target string,
if you're afraid appending to an unbounded string is too slow for your
purpose.

Greetings,

Jacob
-- 
Atheism is a non-prophet organisation.