**Mail Archives: djgpp/1998/01/31/03:54:05**
Nate Eldredge wrote:
>
> Seems to me the one we're interested
> in here is the one that's "the set of real numbers plus positive and
> negative infinity". To me at least, it's not clear how one would actually
> get this to work.
>
Well, I suppose you could #define two symbols +INF and -INF, trap any
division by zero (ie check before you divide, or trap the exception),
check once you have one whether the numerator is positive or negative and
return +INF or -INF accordingly. But this would mean redefining most
simple arithmetic functions, so that they handle these two new symbols
(and the new exceptions these new operations may provoke). So, I don't
quite see the point in using them.
In math, these symbols are often used to simplify formulae or theorems:
when talking about the limits of real functions, for instance, you
usually have to separate two cases: finite and infinite. Extended real
simplify the formulation by bundling the two cases together. However,
they are little more than symbolic conventions.
Francois

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