Re: What's syntax for a case statement?

["David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>]

Hi Alan,

Just a small nit, but <name-of-a-descrete variable>  in your case statement
syntax definition would be more
nearly correct if it said <discrete-expression>  -- e.g., a function call
returning a discrete value.

David C. Hoos, Sr.,

Alan Brain <aebrain@dynamite.com.au> wrote in article
<33A0B0BE.30A8@dynamite.com.au>...
> 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? 
> -- 
> aebrain@dynamite.com.au     <> <>    How doth the little Crocodile
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