In this PR <https://github.com/sympy/sympy/pull/17146> `Range` has been
modified to accept symbolic start, stop and step values, e.g. `Range(x, y,
z)`. One of the decisions that needs to be made is whether such Ranges
should return the symbolic logical statement corresponding to a given
attribute or not.
e.g. the piecewise-folded version of `Range(x, y, z).inf` is
Piecewise(
(nan, ceiling((-x + y)/z) <= 0),
(x, z > 0),
(x + z*ceiling((-x + y)/z) - z, Ne(x, x + 1)),
(y - z, True))
The problem is that the nan result is really not the inf...it is used to
indicate that inf is not defined under conditions that would lead to an
EmptySet, e.g. x=z=1,y=0. Is this of any value or should Range with symbols
just raise a ValueError if a property cannot be given as a simple
expression?
/c
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