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From: Alan Brain <aebrain@dynamite.com.au>
Subject: Re: What's syntax for a case statement?
Date: 1997/06/12
Message-ID: <33A0B0BE.30A8@dynamite.com.au>#1/1
X-Deja-AN: 247841551
References: <5nk6gu$gbp@prometheus.acsu.buffalo.edu>
 <5nllti$lgb@zdi.informatik.uni-stuttgart.de>
Organization: @Home
Reply-To: aebrain@dynamite.com.au
Newsgroups: comp.lang.ada
Date: 1997-06-12T00:00:00+00:00
List-Id: <comp.lang.ada>


Wolfgang Gellerich wrote:
> 
> In article <5nk6gu$gbp@prometheus.acsu.buffalo.edu>, sbmoore@cs.buffalo.edu (Scott B Moore) writes:
> |> I'm new to Ada and I can't find the syntax for a case statement.  Any help?
> 
> Probably, you will need an introduction/ description of Ada - try "Programming
> in Ada95" by John Barnes.

I agree, it's an excellent book, one I'd highly recommend. I've been
using Barnes' "Programming in Ada" for many years, both to teach, and as
a reference for rarely-used constructs and predefined specifications.

BTW, the syntax is

case < name-of-a-descrete variable> is
  when <selection1> => <sequence of statements>;
  when <selection2>  | <selection3> => <sequence of statements>;
  when <selection4>..<selection5> => <sequence of statements>;
 [when others       => <sequence of statements>;
end case;

Examples:
Assuming you have
type TRAFFIC_LIGHT_TYPE is (Red,Green,Amber);
and a variable
ONCOMING_LIGHTS : TRAFFIC_LIGHT_TYPE;      

then you could have

case ONCOMING_LIGHTS is
  when Red  | Amber => STOP(THE_CAR);
  when Green =>
              if ALREADY_STOPPED(THE_CAR) then
                 START(THE_CAR);
              end if;
end case;

or

case ONCOMING_LIGHTS is
 
  when Green =>
              if ALREADY_STOPPED(THE_CAR) then
                 START(THE_CAR);
              end if;

  when others => STOP(THE_CAR);

end case;

Other examples:
ThisLetter : CHARACTER;

case ThisLetter is
  when 'a'..'z' => CHANGE_TO_UPPERCASE(ThisLetter);
  when others   => null;
end case;

ThisInteger : INTEGER;

case ThisInteger is
  when -37..2 => <sequence of statements>
  when 3 | 5  => <some other sequence of statements>
  when 6      => <yet another sequence of statements>
  when others => <and the default sequence of statements>
end case;

OK? 
-- 
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