integer types

[Chris Torek]

Actually, there are a couple of different problems to be solved, and
subranges don't seem to be the right solution for all of them.

1.  You want a variable whose value is to always be contained within
    some particular range (e.g., array indicies).  Subrange types
    (especially runtime-checked types) are nice.

2.  You want a variable whose value can be in *at least* some particular
    range.  Here subrange types that *are not* checked at run time
    seem to work well (though if there is no checking, calling it a
    subrange seems misleading, to me).

3.  You want a variable whose value is in the largest possible range.
    Here subranges fail miserably, because you can't write
    [-infinity..infinity], and even if you could, the machine probably
    wouldn't support *that* (we won't mention lisp bignums).  If you
    have a ``minint'' and ``maxint'' that might work, but perhaps the
    machine can (with some speed degradation perhaps) support something
    bigger than ``integers''.

Anyway, subranges have their uses.  But since C hasn't got subranges,
if you want (1) or (2), use typedefs, preferably in machine-dependent
header files.  In fact, typedefs will work for (3) also.  So why aren't
you using them?  :-)
-- 
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In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
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