Re: Disallowing Pre-Defined Operations

["Jean-Pierre Rosen" <rosen.adalog@wanadoo.fr>]

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Charles H. Sampson <claveman@cod.nosc.mil> a �crit dans le message :
8a9eeg$qtv$1@newpoisson.nosc.mil...
>      During the deliberations that led to Ada 95, was a mechanism for
> disallowing the pre-defined operations of a type considered?  By "disal-
> lowing" I mean some way of informing the compiler that an attempt to use
> a certain pre-defined operation is a compile-time error.  Did anyone
> even ask for it?  (Obviously I didn't, even though I've thought since
> the mid-eighties that it would be a useful capability to have.)

Not only was it considered - it's there.

>      As an example of what I'm talking about, consider a package that
> implements three distinct floating-points types for measuring length,
> area, and volume.  The pre-defined "+" and "-" are acceptable and there
> are obvious redefinitions of "*" and "/" in some cases.  However, the
> pre-defined "/" for operands of the same type don't make sense and it
> would be nice to get a compile-time warning if one of them is used.

function "/" (L, R : Length) return length is abstract;

(but yes, the predefined one may reappear in generics, but that's a good
thing; it allows you to use predefined math libs for example).

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           J-P. Rosen (Rosen.Adalog@wanadoo.fr)
Visit Adalog's web site at http://pro.wanadoo.fr/adalog