sympy: Fixes a failing doctest.

details: http://hg.sympy.org/sympy/rev/81598ff521f5 changeset: 1850:81598ff521f5 user: Ondrej Certik <[EMAIL PROTECTED]> date: Tue Nov 04 23:18:16 2008 +0100 description: Fixes a failing doctest. Everything works, only the doctest should have been adapted in the previous patch. diffs

sympy: Improve printing system

details: http://hg.sympy.org/sympy/rev/aaaf53f1c529 changeset: 1851:aaaf53f1c529 user: Sebastian Kr?mer <[EMAIL PROTECTED]> date: Tue Nov 04 18:04:02 2008 -0800 description: Improve printing system - Printer._depth was not needed - Raise exception when printing method returns None. T