Re: Problem with Patterns and Integrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg123248] Re: Problem with Patterns and Integrate*From*: Armand Tamzarian <mike.honeychurch at gmail.com>*Date*: Tue, 29 Nov 2011 07:03:57 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <javpbs$jbk$1@smc.vnet.net>

On Nov 28, 9:55 pm, Jack McInerney <ejmciner... at gmail.com> wrote: > There is something about using patterns that I don't understand, and > am hoping someone can shed some light. Here is an example of my > problem. Say I have a function f[x] and I take the derivative of it. > I can then integrate it and get f[x] back: > > In[167]:= expr = D[ f[x], x ] > Out[167]= f=E2=80=B2[x] > > In[168]:= Integrate[expr, x] > Out[168]= f[x] > > If I use a ReplaceAll and a pattern to do the integration, the > Integrate function treats f'[x] as a constant and returns the wrong > answer: > > In[169]:= expr /. func_ -> Integrate[func,x] > Out[169]= x f=E2=80=B2[x] > > Any thoughts as to what I am doing wrong? > > Jack Jack you need to use RuleDelayed for this operation expr /. func_ :> Integrate[func,x] Mike