Re: types and subranges, was New Book: The School of Niklaus Wirth

<gdemont@my-deja.com> wrote:
>
> Now you have to decide what to do with an expression like (-i)
> for a "subrange" like 0..100. To convert to a larger range,
> to wrap or to detect a range error ?...


The Ada solution is:
1) All intermediate results are of type universal_integer, which is
infinite-precision arithmetic (the compiler can infer how many bits of
precision are really needed, so this doesn't involve dynamic data
structures).
2) Run-time checks (and possibly an exception) whenever such a value is
assigned to an ordinary integer variable (or parameter).


I find this quite reasonable, though it does make the usual arithmetic
operators special (they accept universal_integer as parameters, so they
cannot be user-defined).


Regards,
Joachim

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