On Mon, 18 Jun 2001, Do Hoang Son wrote:
Hmmm, I don't know. Just look at Maple
c:=ln(x*y)*z; subs(ln=foo,c); foo(x*y)*z
or in Mathematica
In[1]:= c=Log[x*y]*z
Out[1]= z Log[x y]
In[2]:= c//. Log[a__]-> foo[a]
Out[2]= z foo[x y]
There is not any problem there. One offent uses this trick to get rid of troubles that caused by a difined/internal functions.
No, there is not any problem since you haven't really shown us anything that's going to happen later to this new foo() function. Remember last time we talked about such `obvious' transformations? They turned out to be blatant bugs in both Maple and Mathematica. Seriously: please send us a simple example where something like this is needed in order to get around divergences or such and we can discuss alternatives. Cheers -richy. -- Richard Kreckel <Richard.Kreckel@Uni-Mainz.DE> <http://wwwthep.physik.uni-mainz.de/~kreckel/>