Raymond Toy <toy.raymond at gmail.com> writes:
> I noticed when running just the rtest_gamma test, I get two failures:
> limit(erfc(z),z,inf) and limit(erfc(z),z,minf). This doesn't happen when I
> run the entire testsuite. I guess something is leaking into rtest_gamma
> from earlier tests.
>
> However, from a fresh maxima session, maxima cannot determine
> limit(erfc(z),z,inf). But maxima knows limit(erf(z),z,inf) = 1.
>
> Also, erf(inf) -> 1, erfc(inf) -> 0, erf(minf) -> -1, erfc(minf) -> 2. Why
> is that? Compare what happens with tanh(inf) which just returns the noun
> form. Also, sinh(inf) -> sinh(inf).
Hmm, that's interesting. Are there many functions in Maxima that
simplify to numbers when given inf or minf? What I remember from
undergraduate analysis is screaming that f(inf) is pretty much always
nonsense, but maybe there's a convention to use that sort of thing in
other fields? Physics? Engineering? I presume that one just defines
that
f(inf) = lim(f(x), x, inf); ?
I suppose that, since we distinguish inf from infinity, we don't have to
worry about 1 point vs 2 point compactifications of R.
I notice that log(inf) just yields log(inf) (rather than inf). Should we
try to make this feature more uniform?
Rupert
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