Article View: comp.lang.misc
Article #6172Re: Expression Based Language
From: Peter da Silva
Date: Fri, 13 Jan 1989 23:05
Date: Fri, 13 Jan 1989 23:05
53 lines
2030 bytes
2030 bytes
In article <2659@ficc.uu.net> I write:
> >Three comments: First,
> > a = for(s1;e;s2)
> > Is this legal? If e fails, is the value s1?
In article <11398@haddock.ima.isc.com>, karl@haddock.ima.isc.com (Karl Heuer) writes:
> I hadn't thought about that, but it's a reasonable definition -- provided the
> type of s1 matches the type of the body of the for statement.
I don't see why. After all, if you have an expression in current 'C' like:
a = b ? c : d;
The types of c and d don't have to match. Why add an additional constraint
in the extended language?
> It does require
> saving the value of s1 before executing e, which is somewhat couterintuitive.
True. This might be a bit of a problem. I wonder if there's any way around
that...
> >I think the value of a statement with varying types is soluble by looking
> >at the coercion needed to use it in context.
> Context outside of the expression itself? I think that's dangerous ground.
That's the way it currently works for ?:.
> Can you give an example of how one might use this?
int a;
a = switch(nextchar()) {
case '0': case '1': case '2': case '3':
case '4': case '5': case '6': case '7':
result 'O';
case '8': case '9':
result 'D':
case 'A': case 'B': case 'C':
case 'D': case 'E': case 'F':
result 'X';
default:
result -1;
}
--
Peter da Silva, Xenix Support, Ferranti International Controls Corporation.
Work: uunet.uu.net!ficc!peter, peter@ficc.uu.net, +1 713 274 5180. `-_-'
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Opinions may not represent the policies of FICC or the Xenix Support group.
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!ficc!peter From: peter@ficc.uu.net (Peter da Silva) Newsgroups: comp.lang.misc Subject: Re: Expression Based Language Message-ID: <2734@ficc.uu.net> Date: 13 Jan 89 23:05:58 GMT References: <3300001@uxg.cso.uiuc.edu> <3290002@hpctdls.HP.COM> <11398@haddock.ima.isc.com> Organization: Xenix Support Lines: 53