On Thu, May 17, 2012 at 12:23 PM, Stavros Macrakis <macrakis at alum.mit.edu>wrote:
> Currently, atan(inf) => %pi/2, but normally you need to apply 1-argument
> limit:
>
> exp(inf) => exp(inf)
> limit(exp(inf)) => inf
>
> atan(inf^2) => atan(inf^2)
> limit(atan(inf^2)) => %pi/2
>
> atan(inf) => inf can get you in to trouble:
>
Presumably you meant %pi/2, not inf.
>
> (atan(inf)-%pi/2)*inf => 0
> but
> limit(atan(x)-%pi/2)*x,x,inf) => -1
>
>
I take this to mean we shouldn't have atan(inf) -> %pi/2. Which means
erf(inf) and friends should just return a noun. But 0*inf always returns
0. Shouldn't we return und for that?
A peek at the code shows that simp-erf has special tests for this. These
should probably be removed, then.
Ray