Re: Problem with Patterns and Integrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg123257] Re: Problem with Patterns and Integrate*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Tue, 29 Nov 2011 07:05:35 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201111281053.FAA19741@smc.vnet.net>

Compare Rule with RuleDelayed func -> Integrate[func, x] func -> func*x func :> Integrate[func, x] func :> Integrate[func, x] expr = D[f[x], x]; expr /. func_ :> Integrate[func, x] f[x] Bob Hanlon On Mon, Nov 28, 2011 at 5:53 AM, Jack McInerney <ejmcinerney 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 >

**References**:**Problem with Patterns and Integrate***From:*Jack McInerney <ejmcinerney@gmail.com>