Subject: Help matching variables and their indices
From: Mike Valenzuela
Date: Mon, 25 Feb 2013 15:01:21 -0700
Okay, I figured something out.
I got some simpler rules working, but I still have a problem (and I think I
know why there is a problem, just not how to get around it) with the
following:
matchdeclare([xx,yy], symbolp)$
matchdeclare([gg,hh,ii,jj], lambda([x], freeof(xx,x))$
defrule(r3, msum(xx[ii])*msum(xx[jj]), "It matches an indexed variable with
the index" = [xx,ii])$
defrule(r4, msum(gg*xx[ii])*msum(xx[jj]), "R4 matches")$
r3( msum( x[i]) * msum( x[j]) );
r4( msum(2*x[i]) * msum( x[j]) );
r3 matches, but r4 does not match. I suspect that gg is being greedy.
However, I am unsure how to "nest" matches so that gg is free of xx.
On Mon, Feb 25, 2013 at 2:49 PM, Mike Valenzuela <mickle.mouse at gmail.com>wrote:
> Hello again,
>
> I'm sorry if the community is getting tired of many of my questions, but I
> think Maxima could use a tutorial on writing custom rules.
>
> I have tried something similar using the following:
> (%i6) matchdeclare([aa,bb,ii,jj],true)$
> (%i7) matchdeclare([xx,yy], symbolp)$
> (%i8) defrule(sum_power_collapse,
> msum(xx[ii],ii,aa,bb)*msum(xx[jj],jj,aa,bb), msum(xx[ii],ii,aa,bb)^2)$
> % defmatch: xx[aa] will be matched uniquely since sub-parts would
> otherwise be ambigious.
>
> (%i9) apply1( msum(x[i],i,b,c)*msum(x[j],j,b,c), sum_power_collapse);
> (%o9) msum(x[i],a,b,c)*msum(x[j],j,b,c)
>
> I had hoped the outcome would have been: msum(x[i],a,b,c)^2. However, you
> can see it is not working as I had hoped. I am not sure if I am overlooking
> something or a different approach is needed.
>
> Thanks in advance for any advice.
>
>