Hold and Simplify

*To*: mathgroup at smc.vnet.net*Subject*: [mg77143] Hold and Simplify*From*: "news.inode.at" <paul.g.schneider at google.com>*Date*: Tue, 5 Jun 2007 06:25:56 -0400 (EDT)

Hi, I would like to change Exponential functions of sums to products of exponential functions. From reading postings from the year 2004 I tried the following: f[Exp[x_ + y_]] := Exp[x + y] /. Exp[a_ + b_] :> HoldForm[Exp[x]*Exp[y]]; Simplify[Exp[a + b], TransformationFunctions -> f] Unfortunately this gave me Exp[a+b] I had more luck with rule = {Exp[a_ + b_] -> f[Exp[a + b]]} ReplaceRepeated[Exp[a + b], rule] which gave me Exp[a]Exp[b] Trying ReplaceRepeated[Exp[a + b + c], rule] gave me: Exp[a]Exp[b+c] Why doesn't the TransformationFunction trick work? Why does ReplacedRepeated stop? My ultimate goal would be the following: (I need to transfer large formulae into C code and would like to avoid use of exponential function as much as possible) myreplacelist={Exp[var1]->expvar1, Exp[var2]->expvar2} myformula=Exp[2 var1 - 3 var2 + a * Exp[var1]]; ultimate rule applied to my formula gives: expvar1 * expvar1 / (expvar2 * expvar2 * expvar2) * Exp[a expvar1] Thanks for your time! best, Paul

**Follow-Ups**:**Re: Hold and Simplify***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>