Re: The right way to handle this difference in Ada

["Björn Persson" <spam-away@nowhere.nil>]

vic wrote:

> a: unsigned_int_12_type;
> b: unsigned_int_12_type;
> 
> If the code must perform a difference between a and b, say:
> 
> c := a-b
> 
> 1) which should be the type of c? I think it should be something like:
> 
> type signed_int_12_type is range -unsigned_int_12'last ..
> unsigned_int_12'last.

It all depends on what values are sensible for c to have. If for example 
c should never be negative, then it's an error if b is greater than a in 
the subtraction. Then you can declare c as unsigned_int_12_type, and if 
the subtraction ever yields a negative value you'll get a Constraint_Error.

-- 
Björn Persson                              PGP key A88682FD
                    omb jor ers @sv ge.
                    r o.b n.p son eri nu