Rupert,
I tried the tdzero / tdpn route. Are you sure the tdpn mechanism works? I get an infinite loop with
integrate(a^(p*x) * b^(q*x) * c^(r*x),x).
OK:
(%i2) integrate(a^(p*x) * b^(q*x),x);
Is log(b)*q/(log(a)*p) equal to -1?
no;
No OK:
(%o2) (a^(p*x))^(log(b)*q/(log(a)*p)+1)/(log(a)*p*(log(b)*q/(log(a)*p)+1))
(%i3) integrate(a^(p*x) * b^(q*x) * c^(r*x),x);
Is log(c)*r/(log(a)*p)+log(b)*q/(log(a)*p) equal to -1?
no;
Is log(c)*r/(log(a)*p)+log(b)*q/(log(a)*p) equal to -1?
no;
Is log(c)*r/(log(a)*p)+log(b)*q/(log(a)*p) equal to -1?
no;
/* Give up and answer yes: */
Is log(c)*r/(log(a)*p)+log(b)*q/(log(a)*p) equal to -1?
yes;
(%o3) x
--Barton
My code
(defun $askequal (a b)
(let ((answer (meqp a b))) ; presumably handles mbags and extended reals.
(setq answer
(cond ((eq answer t) '$yes)
((eq answer nil) '$no)
(t (retrieve `((mtext) "Is " ,a " equal to " ,b "?") nil))))
(cond ((eq answer '$no)
(print "no branch")
(tdpn (sub a b))
answer)
((eq answer '$yes)
(print "yes branch")
(tdzero (sub a b))
answer)
(t
(mtell "Please answer either yes or no.")
($askequal a b)))))
;; integrate(x^n,x) = if n # -1 then x^(n+1)/(n+1) else logmabs(x).
(defun integrate-mexpt (x n n-is-minus-one)
(cond ((or (eq '$yes n-is-minus-one) (eq t (meqp n -1)))
(logmabs x)) ; that's log(abs(x)) when logabs is true, and log(x) otherwise.
((eq (eq '$no n-is-minus-one) (mnqp n -1))
(setq n (add n 1))
(div (take '(mexpt) x n) n))
(t (integrate-mexpt x n ($askequal n -1)))))
________________________________________
Just because this is still in my head: This behaves rather differently
>From $asksign, since it doesn't remember what it's been told. I guess
you also want a call to tdzero or tdpn with the difference between the
two terms?
Rupert
_______________________________________________
Maxima mailing list
Maxima at math.utexas.edu
http://www.math.utexas.edu/mailman/listinfo/maxima