Comment #16 on issue 2552 by [email protected]: (1/(x*y)).subs(x*y, whatever)
doesn't work
http://code.google.com/p/sympy/issues/detail?id=2552
Thanks for clarifications. All this must be pointed out in documentation
later.
Well, I think it's clear that we should either automatically convert
(1/x)*(1/y) to 1/(x*y) or 1/(x*y) to (1/x)*(1/y) (otherwise, very simple
cancelations will not work).
I suppose that it is needed not only for the simplifications theme
(cancelations in particular), but rather for the expressions's hashe's
equality also. Is not it?
Otherwise, I don't exactly understood why do not use this automatic
conversion only in the simplification process.
I mean that if we did not have this conversion then (rough off this
conversion) only equality (==) procedure crashes (because Basic hash
calculation is primitively the hash of the structure of the classes and
hashes ofarguments). But the simplification core could convert the
expression as it is more convenient independently. And hash's calculation
could be independently too.
This was remark about reasons.
About the substitution:
How you think about the case of '(x**n*y**m).subs(x*y, whatever)' (e.g. n <
m).
What must must be the correct result in this case?
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