sympy/sympy — pull request #1088 by rlamy (2012-02-26 19:57:14+00:00)
Title: Set.contains

This makes a few changes related to [issue 3095](http://code.google.com/p/sympy/issues/detail?id=3095), with the combined effect that Set.contains is now supposed to return a symbolic boolean result (whose actual type can be Boolean, bool or Relational), which is necessary groundwork to allow the implementation of BooleanTrue and BooleanFalse, cf. [issue 2531](http://code.google.com/p/sympy/issues/detail?id=2531).