> > As for encoding a sum over all pairs of indices, there is the >
> complication that
> the official OMCDs aren't fond of expressing > things using binder symbols
> (even
> if the standard supports the > concept of such), so one typically has to
> wrap the
> body up in a > lambda before feeding it to a summation symbol; sort of like
> >
> writing $\sum_{[a,b]} f$ rather than $\sum_{k=a}^b f(k)$. Thus we > get
>
> Thanks for the example. That's in fact the kind of information I was looking
> for:
> general design principles that help finding the right way to express things.
>
> For the particular case of "sum", I find the definition in arith1 a bit vague:
>
> An operator taking two arguments, the first being the range of
> summation, e.g. an integral interval, ...
>
> There is no definition of "range of summation", just an example. You use a
> set in
> your example, which is fine, but there's nothing in the definition of "sum"
> that
> tells me that sets are a valid specification for a "range of summation".
If by "set" you mean the use of { } in the example above then I think that is
part of the TeX syntax used to present the example and does not imply a set.
Francis
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