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From: "Martin Dowie" <martin.dowie@btopenworld.com>
Newsgroups: comp.lang.ada
Subject: New limited range type?
Date: Fri, 7 Nov 2003 15:51:28 +0000 (UTC)
Organization: BT Openworld
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Xref: archiver1.google.com comp.lang.ada:2205
Date: 2003-11-07T15:51:28+00:00
List-Id: <comp.lang.ada>

Ok, as we're in "my favourite thing I'd like in Ada" season, here's mine...

I'd like to be able to declare integer/float/fixed/decimal types that are
limited, at both ends, and never raise exceptions, e.g.

   type Safe_Degrees is
      digits 6 limited range -180.0 .. +180.0;  -- new use of 'limited'

such that

declare
   A, B, C : Safe_Degrees;
begin
   B := 170.0;
   C := 50.0;
   A := B + C;
   -- A equals +180.0 after this statement
   ...
end;

We limit values like this all the time (we're not allowed exceptions)
and although we can write and instantiate generics to help, it's still
a pain.

Could even prove useful in things like SPARK?

Flames welcome! :-)