[m-dev.] for review: counter.m

[Mark Anthony BROWN]

Zoltan Somogyi writes:
> +
> +:- type counter.
> +
> +	% counter_init(N, Counter) returns a counter whose first allocation
> +	% will be the integer N.
> +:- pred counter__init(int::in, counter::out) is det.
> +
> +	% counter__allocate(N, Counter0, Counter) takes a counter, and
> +	% returns (a) the next integer to be allocated from that counter,
> +	% and (b) the updated state of the counter.
> +:- pred counter__allocate(int::out, counter::in, counter::out) is det.
> +

Is it worth changing the type to

	:- type counter(T).

and using the type parameter for some extra type safety, similarly
to what is done in varset.m?  This would allow users to ensure that
a counter initialized for one purpose is not accidentally used
for another purpose.  The above counter could be defined as

	:- type counter == counter(generic).

for some suitable type `generic'.

Cheers,
Mark.
-- 
Mark Brown, PhD student            )O+  |  "Another of Fortran's breakthroughs
(m.brown at cs.mu.oz.au)                   |  was the GOTO statement, which was...
Dept. of Computer Science and Software  |  uniquely simple and understandable"
Engineering, University of Melbourne    |              -- IEEE, 1994
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