5<a<50 (was:Additions to C - range checking)

[steve at jplgodo.UUCP]

In article <7000 at boring.mcvax.UUCP>, jack at mcvax.uucp (Jack Jansen) writes:
> 
> In article <155 at daisy.warwick.UUCP> cudcv at daisy.warwick.ac.uk (Rob McMahon) writes:
> >In article <523 at ccird1.UUCP> rb at ccird1.UUCP (Rex Ballard) writes:
> >>
> >>if (5<a<50) do_something(a);
> >>
> >...
> >>
> >>Is this impossible to parse?
> >
> >This was in BCPL, and was a GOOD IDEA.
> 
> Yes, it is nice from a users standpoint, but if you want to define
> the semantics of this operator in a reasonable way, it becomes
> difficult. The only way out I see is to let expressions have *two*
> values: an ordinary one, and a success/failure indication. Then you
> can let the value of 'a<b' be 'b', and the operator return 'success'
> when a is less than b. I remember seeing something about a language that
> had such semantics, can't remember which one, however.

Icon does just such a thing.  Expressions have both a success/fail value
and their "normal" value.
-- 

...smeagol\			Steve Schlaifer
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