I hope not to be bugging you too much if I ask you some details about
your code... It works fine for my purpose, but for me it is not so
elementary to understand as you said before... I thougth I did
understand it, but it's not so... my ignorance...
I've also noticed that ratlimit is as slow as tlimit if I do
expand(u), it's because of its dependance on num and denom? Moreover,
these two functions yields different results if called on a factored
or an expanded expression. Ratlimit gets rid of these problems?