Updates:
Cc: ronan.l...@gmail.com christian.muise
Comment #7 on issue 2070 by asmeurer: All elements of .args should be Basic
http://code.google.com/p/sympy/issues/detail?id=2070
Well, first off, would Basic True and False objects be useful? Maybe
Ronan, Christian, or someone else interested in the logic stuff can answer
this.
If not, I think the cleanest solution (maybe the cleanest solution anyway)
would be to do a similar thing that we did for Integral. If an expression
is an "otherwise" expression, just put it in the .args instead of an
ExprCondPair. So, for example, the .args for the Piecewise in [23] would
be (ExprCondPair(x, x < 1), y). Then it would be understood that if an
element of .args is not an ExprCondPair, it is for the "otherwise"
condition. Also, since "otherwise" can occur only once per Piecewise, I
think we should normalize it to always be the last item in .args. The
reason is that rebuilding from .args has to work too, so we would have to
allow Piecewise((x, x < 1), y) to return the same thing as Piecewise((x, x
< 1), (y, True)). By the way, this is a similar syntax that Maple uses for
piecewise (except it does not require each pair to be grouped with a tuple,
it just has piecewise(cond1, expr1, …, condn, exprn, expr_otherwise)
(actually, our syntax is better in at least one respect, which is that it
isn't backwards).
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