Simplify[] shortcoming
- To: mathgroup at smc.vnet.net
- Subject: [mg21525] Simplify[] shortcoming
- From: Gianluca Gorni <gorni at dimi.uniud.it>
- Date: Fri, 14 Jan 2000 02:43:40 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Hello!
I have run into a simple expression for which both Simplify and
FullSimplify cannot see an easy simplification:
expr = (3*x + (x - y)*Log[x] + (x - y)*Log[-1 + y/x])/(x - y);
You can see that the factors (x-y) cancel out with the denominator.
So you can write expr as
(3*x)/(x - y) + Log[x] + Log[-1 + y/x]
which has a LeafCount of 21, while expr scored 34. Nevertheless,
Simplify[] leaves expr as it was.
FullSimplify[expr] does collect (x-y) in the numerator, but still
the LeafCount is 29.
My version is Mathematica 4 on MacOS.
Gianluca Gorni