Comment #125 on issue 1694 by nicolas.pourcelot: solve has many issues with
fractions
http://code.google.com/p/sympy/issues/detail?id=1694
Ok, Chris, I've seen your patch (sympy/functions/elementary/exponential.py).
class log(Function):
...
def as_numer_denom(self):
n, d = self.args[0].as_numer_denom()
- if d is S.One:
- return self.func(n), d
- return (self.func(n) - self.func(d)).as_numer_denom()
+ if d != 1:
+ selfx = self.expand(log=1)
+ if selfx.func != self.func:
+ return selfx.as_numer_denom()
+ return self, S.One
This solves the problem of doing log(x/y) == log(x) - log(y) without
checking x and y assumptions.
However, it will still expand log(x/y) if x>0 and y>0.
While this is perfectly correct, I can't see the point of doing this.
Personally, I'd expect log(x/y).as_numer_denom() to simply return
(log(x/y), 1) in any case.
Did I miss something ?
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