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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Math on dimensioned quantities
Date: 1996/07/10
Message-ID: <DuB08H.2HI@world.std.com>#1/1
X-Deja-AN: 167493013
references: <9607091345.AA03915@most>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.ada
Date: 1996-07-10T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <9607091345.AA03915@most>,
W. Wesley Groleau (Wes) <wwgrol@PSESERV3.FW.HAC.COM> wrote:
>writers listening?--how about a pragma similar to
>
>   pragma Disallow ( Operation => "*", For_Type => Inch );

How about:

    function "*"(X, Y: Inches) return Inches is <>;

?  Then this particular "*" is abstract and therefore can't be called,
and this is checked at compile time.  You can still multiply
inches*inches to get square-inches.  It's annoying that you might have
to declare lots of "is <>" functions, but I think it does solve the
problem.

Make sure this is declared in the same package as type Inches; otherwise
all kinds of weirdness can happen.

- Bob