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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Simple ADA/C Question
Date: 1997/03/06
Message-ID: <dewar.857692733@merv>#1/1
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Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-03-06T00:00:00+00:00
List-Id: <comp.lang.ada>


Keith said

<<Hmm.  I find the "Assertion" version easier to read, but to each his own.>>

    Maybe, but my form is guaranteed to give an error message, the assert
    form is not even guaranteed to give a warning (which would in any csae
    be overlooked if warnings were suppressed)

<<In your example, I'd make X a named number rather than an Integer
variable, to make it clearer that the expression is static and therefore
illegal if it raises an exception.  The rules for static expressions
are tricky enough that it's worth being more explicit.>>

    No point in encouraging the (I think unwarranted) viewpoint that the
    rules about static expressions are complex by unnecessary concessions
    to some imagined confusion.
     
           1 / 0

    is an illegal expression. It is illegal quite independent of the
    context in which it occurs, and Ada 95 programmers should understand
    this point clearly!

<<Actually here might be a nice form of the assertion:>>

    Check_Int_Size :
      Compile_Time_Assert := Require / (int'size = Integer'Size);

<<So, Robert, would you argue that Interfaces.C.int is unnecessary, and
that code should always assume that int and Integer are the same size?>>

    Of course not! Arguing that you can sometimes use X instead of Y has
    nothing to do with arguing that Y should never be used! 

<<If not, when is it appropriate to use Interfaces.C.int?>>

    If you are writing a text book, or if you want to be really fanatical
    about being portable to arbitrary unknown compilers in the future (in
    practice, I suspect that a decision to make int /= Integer would break
    so much code that it might be quite unwise :-) 

    P.S. All Aonix products have int'size = integer'size

    Note: Integer has a special place in Ada 95 because of its use in
    type String, so it is hard to get away from completely!