sympy/sympy — pull request #1591 by smichr (2012-10-22 00:55:40+00:00)
Title: S(3).match(1/w) -> {w: 1/3}

A fairly conservative condition had to be applied to the pattern
that is being applied. If if `sb.is_Atom and se.is_Atom:` is left
out then recursive errors abound.