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From: "Mike Silva" <mjsilva@jps.net>
Subject: Re: Modular type. What is it and why?
Date: 1999/04/06
Message-ID: <7ede2p$pd1$1@its.hooked.net>#1/1
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References: <7ean3c$79m$1@eol.dd.chalmers.se> <7eb2iq$jc3@hobbes.crc.com>
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Newsgroups: comp.lang.ada
Date: 1999-04-06T00:00:00+00:00
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David C. Hoos, Sr. wrote in message <7eb2iq$jc3@hobbes.crc.com>...
<....>
>There are many uses for such a type -- e.g., the index of a circular array,
or a representation of the days of the week...

One of the little "goodies" I discovered in coming from C to Ada are modular
types.  I often had to write code like:

switch ( key )
{
   case ARROW_DOWN:
      if ( index < ( NUM_ELEMENTS - 1 ) )
         index++;
      else
         index = 0;
      break;
   case ARROW_UP:
      if ( index > 0 )
         index = NUM_ELEMENTS - 1;
      else
         index--;
      break;
}

Now with Ada I'll be able to write (assuming 'index' is the appropriate
modular type):

case ( key ) is
   when ARROW_DOWN =>
      index := index + 1;
   when ARROW_UP =>
      index := index - 1;
end case;

Now -that's- what I call progress!

Mike