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Re: Extending Integrate[]

• To: mathgroup at smc.vnet.net
• Subject: [mg87789] Re: Extending Integrate[]
• From: dh <dh at metrohm.ch>
• Date: Wed, 16 Apr 2008 22:34:22 -0400 (EDT)
• References: <fu4lnj$si9$1@smc.vnet.net>

Hi Szabolcs,

it looks like mathematica does not automatically distribute your rule 

over Plus. This comes a bit as a surprise. But you can teach it. If you 

additionally give the following rule:

Integrate[a_+b_,x_]:=Integrate[a,x]+Integrate[b,x]

then your example works. Of course you also need linearity.

hope this helps, Daniel



Szabolcs Horvát wrote:

> According to the documentation it is possible to extend Integrate[] with 

> new rules:

> 

> http://reference.wolfram.com/mathematica/tutorial/IntegralsThatCanAndCannotBeDone.html

> 

> The specific example that is given is:

> 

> Unprotect[Integrate]

> 

> Integrate[Sin[Sin[a_. + b_. x_]], x_] := Jones[a, x]/b

> 

> Now Integrate[Sin[Sin[3x]], x] will return Jones[0, x]/3

> 

> But if I try an integrand that is just slightly more complicated, 

> Mathematica returns it unevaluated:

> 

> In[21]:= Integrate[a + Sin[Sin[x]], x]

> Out[21]= Integrate[a + Sin[Sin[x]], x]

> 

> My question is:  Is it really possible to extend Integrate in an 

> intelligent way?  The above example seems to be just simple pattern 

> matching.  It would work with any function, not just Integrate[].  There 

> is nothing new or surprising about it.

> 

> But is it *really* possible to extend Integrate[] with new definitions 

> in a way that Mathematica will use these rules when calculating more 

> complicated Integrals?

> 

> If (as I suspect) it is not possible to do this, then the documentation 

> is a bit misleading ...

>