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From: "Davide" <ppp@ppp.it>
Newsgroups: comp.lang.ada
Subject: Newbie Question: Casting Issue
Date: Tue, 4 May 2004 11:22:03 +0200
Organization: Finmeccanica
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Date: 2004-05-04T11:22:03+02:00
List-Id: <comp.lang.ada>

I need your help, please, to solve a casting issue.

I have an Ada operation, say FLOAT_POINT_OP, which returns a floating point
type, say: FLOAT_POINT_TYPE is digits 9.

The result of this operation must be assigned to a fixed point type
variable, say: FIX_POINT_TYPE is delta 0.0625 range -10.0 .. 36.5.

I cannot use Ada exceptions and I must ensure that the assignment will not
throw a type constraint error at run-time.
Then I perform this check:

FLOAT_VAR >= FLOAT_POINT_TYPE(FIX_POINT_TYPE'FIRST)
and
FLOAT_VAR <= FLOAT_POINT_TYPE(FIX_POINT_TYPE'LAST)

(where FLOAT_VAR is the floating point type result returned by
FLOAT_POINT_OP)

and if the check passes then I perform the "crucial" assignment:

FIX_VAR := FLOAT_VAR.

Do you think it works fine?

Have you better solutions?

My worry is about the FLOAT_POINT_TYPE(FIX_POINT_TYPE'FIRST) casting. In
particular about the possibility of an introduction of additional decimal
digits, after the last decimal digit of the FIX_POINT_TYPE bounds. I think
that everything should work if the casting preserves at least the number of
decimal digits specified for delta (in this case 4 digits, being delta =
0.0625) adding possible digits after the fourth. There is some Ada standard
directive about that?

Thank you.