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Re: Problem with transformation rule of a function -- Another one

• To: mathgroup at smc.vnet.net
• Subject: [mg53509] Re: [mg53467] Problem with transformation rule of a function -- Another one
• From: Alain Cochard <alain at geophysik.uni-muenchen.de>
• Date: Sat, 15 Jan 2005 01:44:08 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

Thank you so much to those who answered.  Now, here is another one.

The following works as I expect:

     In[1]:= expr=Integrate[D[g[x,t],t],{x,0,1}]

			(0,1)
     Out[1]= Integrate[g     [x, t], {x, 0, 1}]

     In[2]:= g[x_,t_]:= x f[t]

     In[3]:= expr

	     f'[t]
     Out[3]= -----
	       2

Now I would like to use a transformation rule instead, like in:

     In[1]:= expr=Integrate[D[g[x,t],t],{x,0,1}] ; 

     In[2]:= expr/. g[x,t]->x f[t]

			(0,1)
     Out[2]= Integrate[g     [x, t], {x, 0, 1}]

I tried various alternatives (with "//", ":>", "Evaluate", using "_"
or not, with "Hold/ReleaseHold" -- although not in a fully systematic
way, I admit) without success.  Is it feasible?

Thanks,
Alain

• Follow-Ups:
  • Re: Re: Problem with transformation rule of a function -- Another one
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>
  • Re: Re: Problem with transformation rule of a function -- Another one
    • From: DrBob <drbob@bigfoot.com>