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From: Ted Dennison <dennison@telepath.com>
Subject: Re: Case Sensitivity
Date: 2000/05/11
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In article <958056490.47876@hearts.q-net.net.au>,
  "Cameron McShane" <cazza@aceonline.com.au> wrote:
> Hey
>
> I am doing a project for Uni, and am a bit stuck.
>
> We need a menu that needs to be case-'in'sensitive. I am using an
enumerated
> data type for the 3 menu options ie:
>
>     type Menu_Options is (buy, read, done)
>
> If the user is to be allowed to enter Buy or BUY or bUy - etc, do I
need to
> make the data type
>
>     type Menu_Options is (buy, Buy, bUY, etc
>
> or is there a way of converting user input to all lower case?

Yes.

In the Latin_1 character collating sequence, it just so happens that the
characters 'a' through 'z' all have the same relative position to each
other as the characters 'A' through 'Z'. The lower-case letters have a
larger value than the upper case letters. (See Ada.Characters.Latin_1)
So the traditional manual way to do this would be to find the difference
in the integer position of an upper case character from that of its
lower-case counterpart (eg: 'A' and 'a'). Then you can add that
difference to the integer position of every upper-case letter you
encounter. Then you just need to find the character value for that
resulting integer position. There are predefined attributes that you can
apply to characters to convert between their character value and their
integer position. (This reads pretty complicated, but the code's really
very simple).

But you don't have to do this manually (unless your teacher wants you
to). Take out your handy-dandy Ada LRM (if you don't have one, there's
one online at http://www.adapower.com ) and look through the routines in
the standard Ada library in Appendix A. There are a couple of sets of
packages in there that provide useful routines for doing this kind of
thing. There are packages for doing lots of other neat stuff too, so be
sure to look through them all.

While you're at it, do yourself a favor and read through appendix K
(Language Defined Attributes). There's lots of vital stuff in there to
make your life easier.

--
T.E.D.

http://www.telepath.com/~dennison/Ted/TED.html


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