I'm trying to define a function f, such that
Then, I tried to evaluate
f[x,y] satisfies none of these two patterns, it is expected that the result will be just
f[x,y]. Nevertheless, in fact, the result is
and I get a error message:
$IterationLimit::itlim: Iteration limit of 4096 exceeded. >>
It seems quite confusing. How could this happen?