Substitution in a function



Hi.

I'm trying to permute some functions w.r.t. the variables they are
using.

For example, I have a function 

(C93) f:u-v+3*w;

(D93) 				  3 w - v + u

then, I "rotate" the vars like this:

(C94) f:f,u=v,v=w,w=u;

(D94) 				 - w + v + 3 u
which is what I want.

But how can I achive it within a function.  If I go

func(p):=( .. stuff ...
	f:u-v+3*w,
	... stuff ..
	f:f,u=v,v=w,w=u,
	... stuff that uses the new f...
)

the substitutions seem to have no effect.  The subst functions seems
only to allow one substitution at a time, so I can't use it, it seems.

Help appreciated

Thanks
Neilen


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