Pattern matching with reals (Standard ML)

Question

Doing this:

fun test a 0.0 = "good"
  | test a b = "bad";

results in an error, but if I change the 0.0 the error goes away. However, I need to match 0.0 and I'm wondering if and how that can be accomplished.

Answer 1

Supposedly it's because real is not an eqtype in SML 97: http://www.smlnj.org/doc/Conversion/types.html#Real-equality