Comment #1 on issue 1928 by basti.kr: Boolean algebra inconsistencies http://code.google.com/p/sympy/issues/detail?id=1928
> * Equivalent required its arguments to have arithmetic comparison > defined.
You also changed its behavior. Before it was: In [1]: Equivalent(x,x,y) Out[1]: Equivalent(x, x, y) Now it gives: In [10]: Equivalent(x,x,y) Out[10]: Equivalent(x, y) Both expressions are equivalent :) but the second is simpler, so I like it. What I don't understand is how Equivalent(x) is mathematically defined. Now it gives in sympy: In [20]: Equivalent(x,x) Out[20]: Equivalent(x) Shouldn't this return True instead?
> * To check for that kind of error, tests in test_boolalg.py use > instances > of Boolean instead of Symbols.
I don't know if there is a general policy, but I saw at least some tests where symbols where just defined once globally and not again and again in every single function.
> * Nand and Nor now call And and Or immediately
Was there some reason why this was written so complicated before? It now definitely gives the right result and it's much simpler to understand. And I also think it's faster than before. So imho this is a good change ;) BTW is there somewhere defined what Nand of more than two elements gives? In sympy it is NOT(AND(...)) but couldn't it also be defined as NAND(x,y,z) = NAND(NAND(x,y),z)?
> * Since Or() is False, the correct value for Nor() is True. > * Xor stops raising an exception with non-Boolean args. > * Add XOR operator ('^') support for Booleans.
Since this also defines the ^ operator for symbols this is a rather big change. I'm +0 for it. What do others think? Also in this commit you have some trailing whitespaces where you change the gotchas. Since it isn't source code it isn't checked for.
> * Bring test coverage back to 100% >
Everything else looks fine and ready to push ;) Sebastian -- You received this message because you are subscribed to the Google Groups "sympy-issues" group. To post to this group, send email to sympy-iss...@googlegroups.com. To unsubscribe from this group, send email to sympy-issues+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy-issues?hl=en.