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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: generic function and overloading
Date: Thu, 18 Oct 2007 11:58:48 -0400
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Date: 2007-10-18T11:58:48-04:00
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eliben <eliben@gmail.com> writes:

> Hello,
>
> I have a few "hardware" types, for example uint16 and uint32. And I
> want to write a functions that will set or clear bits of such types.
> For example:
>
> function Bit_Set(word: uint16; bitn: natural) return uint16;
>
> function Bit_Set(word: uint16; bitn: natural) return uint16 is
>   mask: uint16 := 2**bitn;
> begin
>   return word or mask;
> end Bit_Set;
>
> However, I realize that such a function would be almost completely
> duplicated for the uint32 type. In C++ I would probably define it as a
> template on the type of the word, and the compiler would do the job
> for me. In Ada, however, when using generics it doesn't seem I can
> leave the same function name for all types (as I would do in
> overloading). I can define a generic Bit_Set, but then I have to
> specialize it for uin16 and uint32 with different function names. Is
> there any way I could combine the effects of generics and overloading
> and get a single Bit_Set for all my types without writing the code N
> times ?

Others answered your main question.

But do you really want to do arithmetic on these types,
as well as setting/clearing bits?  If all you want to
do is set/clear bits, you might want to consider using
a packed array of Boolean.  Then to set the Nth bit you
can say:

    X (N) := True;

Alternatively, a packed array of type Bit, where:

    type Bit is range 0..1;

If the individual bit numbers have some specific meaning,
the index type could be an enumeration type.

- Bob