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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Checking to see if a string is a letter
Date: Tue, 03 Apr 2012 09:26:40 +0100
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Date: 2012-04-03T09:26:40+01:00
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deuteros <deuteros@xrs.net> writes:

> On Tue 03 Apr 2012 01:15:27a, Jeffrey Carter
> <spam.jrcarter.not@spam.not.acm.org> wrote in
> news:jle13q$ale$1@tornado.tornevall.net: 
>
>> What do you mean by "contains a single letter"?
>
> I mean the string contains a single letter and nothing more. For
> example:
>
> a  - Legal
> A  - Legal
> aa - Illegal
> a1 - Illegal

Then for a start the length of the string needs to be 1.

If it is, the first (and only!) character needs to be a lower- or
upper-case letter. There are (at least) three ways of doing this:

* declare an array of Boolean indexed by Character, with the elements
  indexed by letters set to True and the others to False, and index by
  the character to be tested;

* declare two subtypes of character ("Character range 'a' .. 'z'", for
  instance) and check whether the character to be tested is 'in' either
  of the subtypes;

* use the standard library, Ada.Characters.Handling.Is_Letter (probably
  the easiest for you!)