;;; -*-  Mode: Lisp; Package: Maxima; Syntax: Common-Lisp; Base: 10 -*- ;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;     The data in this file contains enhancements.                   ;;;;;
;;;                                                                    ;;;;;
;;;  Copyright (c) 1984,1987 by William Schelter,University of Texas   ;;;;;
;;;     All rights reserved                                            ;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;     (c) Copyright 1982 Massachusetts Institute of Technology         ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(in-package :maxima)

(macsyma-module asum)

(load-macsyma-macros rzmac)

(declare-top (special *a sum *i))

(defmvar $opproperties
    (list* '(mlist simp)
	   ;; This list was obtained by using an existing version of
	   ;; maxima and printing out the value.  It can also be
	   ;; obtained by examining the code below to see what is
	   ;; placed on the OPER variable.
	   '($linear $additive $multiplicative $outative $evenfun $oddfun
	     $commutative $symmetric $antisymmetric $nary $lassociative $rassociative))
  "List of the special operator properties recognized by the Maxima simplifier."
  ;; Don't reset this.  (This was originally a defparameter which
  ;; wouldn't get reset.)
  no-reset
  ;; We probably don't want the user to modify this except via
  ;; define_opproperty.
  :properties ((assign 'neverset)))
  
(loop for (x y) on '(%cot %tan %csc %sin %sec %cos %coth %tanh %csch %sinh %sech %cosh)
   by #'cddr do (putprop x y 'recip) (putprop y x 'recip))

;; polynomial predicates and other such things

(defun poly? (exp var)
  (cond ((or (atom exp) (free exp var)))
	((member (caar exp) '(mtimes mplus) :test #'eq)
	 (do ((exp (cdr exp) (cdr exp)))
	     ((null exp) t)
	   (and (null (poly? (car exp) var)) (return nil))))
	((and (eq (caar exp) 'mexpt)
	      (integerp (caddr exp))
	      (> (caddr exp) 0))
	 (poly? (cadr exp) var))))

(defun smono (x var)
  (smonogen x var t))

(defun smonop (x var)
  (smonogen x var nil))

(defun smonogen (x var fl)	; fl indicates whether to return *a *n
  (cond ((free x var) (and fl (setq *n 0 *a x)) t)
	((atom x) (and fl (setq *n (setq *a 1))) t)
	((and (listp (car x))
	      (eq (caar x) 'mtimes))
	 (do ((x (cdr x) (cdr x))
	      (a '(1)) (n '(0)))
	     ((null x)
	      (and fl (setq *n (addn n nil) *a (muln a nil))) t)
	   (let (*a *n)
	     (if (smonogen (car x) var fl)
		 (and fl (setq a (cons *a a) n (cons *n n)))
		 (return nil)))))
	((and (listp (car x))
	      (eq (caar x) 'mexpt))
	 (cond ((and (free (caddr x) var) (eq (cadr x) var))
		(and fl (setq *n (caddr x) *a 1)) t)))))

;; factorial stuff

(defun gfact (n %m i)
  (cond ((minusp %m) (improper-arg-err %m '$genfact))
	((= %m 0) 1)
	(t (prog (ans)
	      (setq ans n)
	      a (if (= %m 1) (return ans))
	      (setq n (m- n i) %m (1- %m) ans (m* ans n))
	      (go a)))))

;; From Richard Fateman's paper, "Comments on Factorial Programs",
;; http://www.cs.berkeley.edu/~fateman/papers/factorial.pdf
;;
;; k(n,m) = n*(n-m)*(n-2*m)*...
;;
;; (k n 1) is n!
;;
;; This is much faster (3-4 times) than the original factorial
;; function.

(defun factorial (n)
  (labels ((k (n m) 
	     (if (<= n m)
		 n
		 (* (k n (* 2 m))
		    (k (- n m) (* 2 m))))))
    (if (zerop n)
	1
	(k n 1))))

;;; Factorial has mirror symmetry

(defprop mfactorial t commutes-with-conjugate)

(defun simpfact (x y z)
  (oneargcheck x)
  (setq y (simpcheck (cadr x) z))
  (cond ((and (mnump y)
              (eq ($sign y) '$neg)
              (zerop1 (sub (simplify (list '(%truncate) y)) y)))
         ;; Negative integer or a real representation of a negative integer.
         (merror (intl:gettext "factorial: factorial of negative integer ~:M not defined.") y))
        ((or (floatp y)             
             ($bfloatp y)
             (and (not (integerp y))
                  (not (ratnump y))
                  (or (and (complex-number-p y 'float-or-rational-p)
                           (or $numer 
                               (floatp ($realpart y)) 
                               (floatp ($imagpart y))))
                      (and (complex-number-p y 'bigfloat-or-number-p)
                           (or $numer
                               ($bfloatp ($realpart y))
                               ($bfloatp ($imagpart y))))))
             (and (not makef) (ratnump y) (equal (caddr y) 2)))
         ;; Numerically evaluate for real or complex argument in float or
         ;; bigfloat precision using the Gamma function
	 (simplify (list '(%gamma) (add 1 y))))
        ((eq y '$inf) '$inf)
        ((and $factorial_expand
              (mplusp y)
              (integerp (cadr y)))
         ;; factorial(n+m) and m integer. Expand.
         (let ((m (cadr y))
               (n (simplify (cons '(mplus) (cddr y)))))
           (cond ((>= m 0)
                  (mul 
                    (simplify (list '($pochhammer) (add n 1) m))
                    (simplify (list '(mfactorial) n))))
                 ((< m 0)
                  (setq m (- m))
                  (div
                    (mul (power -1 m) (simplify (list '(mfactorial) n)))
                    ;; We factor to get the ordering (n-1)*(n-2)*...
                    ($factor
                      (simplify (list '($pochhammer) (mul -1 n) m))))))))
	((or (not (fixnump y)) (not (> y -1)))
	 (eqtest (list '(mfactorial) y) x))
	((or (minusp $factlim) (not (> y $factlim)))
	 (factorial y))
	(t (eqtest (list '(mfactorial) y) x))))

(defun makegamma1 (e)
  (cond ((atom e) e)
	((eq (caar e) 'mfactorial)
	 (list '(%gamma) (list '(mplus) 1 (makegamma1 (cadr e)))))

	;; Begin code copied from orthopoly/orthopoly-init.lisp
	;; Do pochhammer(x,n) ==> gamma(x+n)/gamma(x),
    ;; but not if x is a negative integer or zero.

	((eq (caar e) '$pochhammer)
	 (let ((x (makegamma1 (nth 1 e)))
	       (n (makegamma1 (nth 2 e))))
	  (if (and (integerp x) (<= x 0))
        e
	    (div (take '(%gamma) (add x n)) (take '(%gamma) x)))))
	 
	;; (gamma(x/z+1)*z^floor(y))/gamma(x/z-floor(y)+1)

	((eq (caar e) '%genfact)
	 (let ((x (makegamma1 (nth 1 e)))
	       (y (makegamma1 (nth 2 e)))
	       (z (makegamma1 (nth 3 e))))
	   (setq y (take '($floor) y))
	   (div 
	    (mul
	     (take '(%gamma) (add (div x z) 1))
	     (power z y))
	    (take '(%gamma) (sub (add (div x z) 1) y)))))
	;; End code copied from orthopoly/orthopoly-init.lisp

        ;; Double factorial

        ((eq (caar e) '%double_factorial)
         (let ((x (makegamma1 (nth 1 e))))
           (mul
             (power
               (div 2 '$%pi)
               (mul
                 (div 1 4)
                 (sub 1 (simplify (list '(%cos) (mul '$%pi x))))))
             (power 2 (div x 2))
             (simplify (list '(%gamma) (add 1 (div x 2)))))))

	((eq (caar e) '%elliptic_kc)
	 ;; Complete elliptic integral of the first kind
	 (cond ((alike1 (cadr e) '((rat simp) 1 2))
		;; K(1/2) = gamma(1/4)/4/sqrt(pi)
		'((mtimes simp) ((rat simp) 1 4)
		  ((mexpt simp) $%pi ((rat simp) -1 2))
		  ((mexpt simp) ((%gamma simp) ((rat simp) 1 4)) 2)))
	       ((or (alike1 (cadr e)
			    '((mtimes simp) ((rat simp) 1 4)
			      ((mplus simp) 2
			       ((mexpt simp) 3 ((rat simp) 1 2)))))
		    (alike1 (cadr e)
			    '((mplus simp) ((rat simp) 1 2)
			      ((mtimes simp) ((rat simp) 1 4)
			       ((mexpt simp) 3 ((rat simp) 1 2)))))
		    (alike1 (cadr e)
			    ;; 1/(8-4*sqrt(3))
			    '((mexpt simp)
			      ((mplus simp) 8
			       ((mtimes simp) -4
				((mexpt simp) 3 ((rat simp) 1 2))))
			      -1)))
		;; K((2+sqrt(3)/4))
		'((mtimes simp) ((rat simp) 1 4)
		  ((mexpt simp) 3 ((rat simp) 1 4))
		  ((mexpt simp) $%pi ((rat simp) -1 2))
		  ((%gamma simp) ((rat simp) 1 6))
		  ((%gamma simp) ((rat simp) 1 3))))
	       ((or (alike1 (cadr e)
			    ;; (2-sqrt(3))/4
			    '((mtimes simp) ((rat simp) 1 4)
			      ((mplus simp) 2
			       ((mtimes simp) -1
				((mexpt simp) 3 ((rat simp) 1 2))))))
		    (alike1 (cadr e)
			    ;; 1/2-sqrt(3)/4
			    '((mplus simp) ((rat simp) 1 2)
			      ((mtimes simp) ((rat simp) -1 4)
			       ((mexpt simp) 3 ((rat simp) 1 2)))))
		    (alike (cadr e)
			   ;; 1/(4*sqrt(3)+8)
			   '((mexpt simp)
			     ((mplus simp) 8
			      ((mtimes simp) 4
			       ((mexpt simp) 3 ((rat simp) 1 2))))
			     -1)))
		;; K((2-sqrt(3))/4)
		'((mtimes simp) ((rat simp) 1 4)
		  ((mexpt simp) 3 ((rat simp) -1 4))
		  ((mexpt simp) $%pi ((rat simp) -1 2))
		  ((%gamma simp) ((rat simp) 1 6))
		  ((%gamma simp) ((rat simp) 1 3))))
	       ((or
		 ;; (3-2*sqrt(2))/(3+2*sqrt(2))
		 (alike1 (cadr e)
			 '((mtimes simp)
			   ((mplus simp) 3 
			    ((mtimes simp) -2 
			     ((mexpt simp) 2 ((rat simp) 1 2))))
			   ((mexpt simp)
			    ((mplus simp) 3 
			     ((mtimes simp) 2
			      ((mexpt simp) 2 ((rat simp) 1 2)))) -1)))
		 ;; 17 - 12*sqrt(2)
		 (alike1 (cadr e)
			 '((mplus simp) 17 
			   ((mtimes simp) -12
			    ((mexpt simp) 2 ((rat simp) 1 2)))))
		 ;;   (2*SQRT(2) - 3)/(2*SQRT(2) + 3)
		 (alike1 (cadr e)
			 '((mtimes simp) -1
			   ((mplus simp) -3
			    ((mtimes simp) 2 
			     ((mexpt simp) 2 ((rat simp) 1 2))))
			   ((mexpt simp)
			    ((mplus simp) 3
			     ((mtimes simp) 2
			      ((mexpt simp) 2 ((rat simp) 1 2))))
			    -1))))
		'((mtimes simp) ((rat simp) 1 8)
		  ((mexpt simp) 2 ((rat simp) -1 2))
		  ((mplus simp) 1 ((mexpt simp) 2 ((rat simp) 1 2)))
		  ((mexpt simp) $%pi ((rat simp) -1 2))
		  ((mexpt simp) ((%gamma simp) ((rat simp) 1 4)) 2)))
	       (t
		;; Give up
		e)))
	((eq (caar e) '%elliptic_ec)
	 ;; Complete elliptic integral of the second kind
	 (cond ((alike1 (cadr e) '((rat simp) 1 2))
		;; 2*E(1/2) - K(1/2) = 2*%pi^(3/2)*gamma(1/4)^(-2)
		'((mplus simp)
		  ((mtimes simp) ((mexpt simp) $%pi ((rat simp) 3 2))
		   ((mexpt simp) 
		    ((%gamma simp irreducible) ((rat simp) 1 4)) -2))
		  ((mtimes simp) ((rat simp) 1 8)
		   ((mexpt simp) $%pi ((rat simp) -1 2))
		   ((mexpt simp) ((%gamma simp) ((rat simp) 1 4)) 2))))
	       ((or (alike1 (cadr e)
			    '((mtimes simp) ((rat simp) 1 4)
			      ((mplus simp) 2
			       ((mtimes simp) -1
				((mexpt simp) 3 ((rat simp) 1 2))))))
		    (alike1 (cadr e)
			    '((mplus simp) ((rat simp) 1 2)
			      ((mtimes simp) ((rat simp) -1 4)
			       ((mexpt simp) 3 ((rat simp) 1 2))))))
		;; E((2-sqrt(3))/4)
		;;
		;; %pi/4/sqrt(3) = K*(E-(sqrt(3)+1)/2/sqrt(3)*K)
		'((mplus simp)
		  ((mtimes simp) ((mexpt simp) 3 ((rat simp) -1 4))
		   ((mexpt simp) $%pi ((rat simp) 3 2))
		   ((mexpt simp) ((%gamma simp) ((rat simp) 1 6)) -1)
		   ((mexpt simp) ((%gamma simp) ((rat simp) 1 3)) -1))
		  ((mtimes simp) ((rat simp) 1 8)
		   ((mexpt simp) 3 ((rat simp) -3 4))
		   ((mexpt simp) $%pi ((rat simp) -1 2))
		   ((%gamma simp) ((rat simp) 1 6))
		   ((%gamma simp) ((rat simp) 1 3)))
		  ((mtimes simp) ((rat simp) 1 8)
		   ((mexpt simp) 3 ((rat simp) -1 4))
		   ((mexpt simp) $%pi ((rat simp) -1 2))
		   ((%gamma simp) ((rat simp) 1 6))
		   ((%gamma simp) ((rat simp) 1 3)))))
	       ((or (alike1 (cadr e)
			    '((mtimes simp) ((rat simp) 1 4)
			      ((mplus simp) 2
			       ((mexpt simp) 3 ((rat simp) 1 2)))))
		    (alike1 (cadr e)
			    '((mplus simp) ((rat simp) 1 2)
			      ((mtimes simp) ((rat simp) 1 4)
			       ((mexpt simp) 3 ((rat simp) 1 2))))))
		;; E((2+sqrt(3))/4)
		;;
		;; %pi*sqrt(3)/4 = K1*(E1-(sqrt(3)-1)/2/sqrt(3)*K1)
		'((mplus simp)
		  ((mtimes simp) 3 ((mexpt simp) 3 ((rat simp) -3 4))
		   ((mexpt simp) $%pi ((rat simp) 3 2))
		   ((mexpt simp) ((%gamma simp) ((rat simp) 1 6)) -1)
		   ((mexpt simp) ((%gamma simp) ((rat simp) 1 3)) -1))
		  ((mtimes simp) ((rat simp) 3 8)
		   ((mexpt simp) 3 ((rat simp) -3 4))
		   ((mexpt simp) $%pi ((rat simp) -1 2))
		   ((%gamma simp) ((rat simp) 1 6))
		   ((%gamma simp) ((rat simp) 1 3)))
		  ((mtimes simp) ((rat simp) -1 8)
		   ((mexpt simp) 3 ((rat simp) -1 4))
		   ((mexpt simp) $%pi ((rat simp) -1 2))
		   ((%gamma simp) ((rat simp) 1 6))
		   ((%gamma simp) ((rat simp) 1 3)))))
	       (t
		e)))
	(t (recur-apply #'makegamma1 e))))

(def-simplifier genfact (x y z)
  (let ((a x)
	(b (take '($floor) y))
	(c z))
    (cond ((and (fixnump a)
                (fixnump b)
                (fixnump c))
           (if (and (> a -1)
                    (> b -1) 
                    (or (<= c a) (= b 0))
                    (<= b (/ a c)))
               (gfact a b c)
               (merror (intl:gettext "genfact: generalized factorial not defined for given arguments."))))
	  (t
	   ;; Give up, we want to return a result with args that are
	   ;; different from the original.  In particular, we want the
	   ;; floor of y if y was real number.  Otherwise, we leave
	   ;; it.
	   (give-up :args (list a
		                (if (and (not (atom b))
				         (eq (caar b) '$floor))
			            (cadr b)
			            b)
		                c))))))

;; sum begins

;; These variables should be initialized where they belong.

;; FIXME: maxtaydiff and *trunclist don't appear to used anywhere.
(defmvar $maxtaydiff 4)
(defvar *trunclist nil)

(defmacro sum-arg (sum)
  `(cadr ,sum))

(defmacro sum-index (sum)
  `(caddr ,sum))

(defmacro sum-lower (sum)
  `(cadddr ,sum))

(defmacro sum-upper (sum)
  `(cadr (cdddr ,sum)))

(defmspec $sum (l)
  (arg-count-check 4 l)
  (setq l (cdr l))
  (dosum (car l) (cadr l) (meval (caddr l)) (meval (cadddr l)) t :evaluate-summand t))


(defmspec $lsum (l)
  (arg-count-check 3 l)
  (setq l (cdr l))
  ;;(or (= (length l) 3) (wna-err '$lsum))
  (let ((form (car l))
	(ind (cadr l))
	(lis (meval (caddr l)))
	(ans 0))
    (or (symbolp ind) (merror (intl:gettext "lsum: second argument must be a variable; found ~M") ind))
    (cond (($listp lis)
	   (loop for v in (cdr lis)
	      with lind = (cons ind nil)
	      for w = (cons v nil)
	      do
	      (setq ans (add* ans  (mbinding (lind w) (meval form)))))
	   ans)
	  (t `((%lsum) ,form ,ind ,lis)))))
    
(defun simpsum (x y z)
  (let (($ratsimpexpons t))
    (setq y (maybe-simplifya (sum-arg x) z)))
  (simpsum1 y (sum-index x) (maybe-simplifya (sum-lower x) z)
	    (maybe-simplifya (sum-upper x) z)))

; This function was SIMPSUM1 until the sum/product code was revised Nov 2005.
; The revised code punts back to this function since this code knows
; some simplifications not handled by the revised code. -- Robert Dodier

(defun simpsum1-save (exp i lo hi)
  (cond ((not (symbolp i)) (merror (intl:gettext "sum: index must be a symbol; found ~M") i))
	((equal lo hi) (mbinding ((list i) (list hi)) (meval exp)))
	((and (atom exp)
	      (not (eq exp i))
	      (getl '%sum '($outative $linear)))
	 (freesum exp lo hi 1))
	((null $simpsum) (list (get '%sum 'msimpind) exp i lo hi))
	((and (or (eq lo '$minf)
		  (alike1 lo '((mtimes simp) -1 $inf)))
	      (equal hi '$inf))
	 (let ((pos-part (simpsum2 exp i 0 '$inf))
	       (neg-part (simpsum2 (maxima-substitute (m- i) i exp) i 1 '$inf)))
	   (cond
	     ((or (eq neg-part '$und)
		  (eq pos-part '$und))
	      '$und)
	     ((eq pos-part '$inf)
	      (if (eq neg-part '$minf) '$und '$inf))
	     ((eq pos-part '$minf)
	      (if (eq neg-part '$inf) '$und '$minf))
	     ((or (eq neg-part '$inf) (eq neg-part '$minf))
	      neg-part)
	     (t (m+ neg-part pos-part)))))
	((or (eq lo '$minf)
	     (alike1 lo '((mtimes simp) -1 '$inf)))
	 (simpsum2 (maxima-substitute (m- i) i exp) i (m- hi) '$inf))
	(t (simpsum2 exp i lo hi))))

;; DOSUM, MEVALSUMARG, DO%SUM -- general principles

;;  - evaluate the summand/productand
;;  - substitute a gensym for the index variable and make assertions (via assume) about the gensym index
;;  - return 0/1 for empty sum/product. sumhack/prodhack are ignored
;;  - distribute sum/product over mbags when listarith = true

(defun dosum (expr ind low hi sump &key (evaluate-summand t))
  (setq low (ratdisrep low) hi (ratdisrep hi)) ;; UGH, GAG WITH ME A SPOON
  (if (not (symbolp ind))
      (merror (intl:gettext "~:M: index must be a symbol; found ~M") (if sump '$sum '$product) ind))
  (unwind-protect
       (prog (u *i lind l*i *hl)
	  (setq lind (cons ind nil))
	  (cond
	    ((not (fixnump (setq *hl (mfuncall '$floor (m- hi low)))))
	     (if evaluate-summand (setq expr (mevalsumarg expr ind low hi)))
	     (return (cons (if sump '(%sum) '(%product))
			   (list expr ind low hi))))
	    ((signp l *hl)
	     (return (if sump 0 1))))
	  (setq *i low l*i (list *i) u (if sump 0 1))
	  lo (setq u
		   (if sump
		       (add u (resimplify (let* ((foo (mbinding (lind l*i) (meval expr)))
						 (bar (subst-if-not-freeof *i ind foo)))
					    bar)))
		       (mul u (resimplify (let* ((foo (mbinding (lind l*i) (meval expr)))
						 (bar (subst-if-not-freeof *i ind foo)))
					    bar)))))
	  (when (zerop *hl) (return u))
	  (setq *hl (1- *hl))
	  (setq *i (car (rplaca l*i (m+ *i 1))))
	  (go lo))))

(defun subst-if-not-freeof (x y expr)
  (if ($freeof y expr)
      ;; suppressing substitution here avoids substituting for
      ;; local variables recognize by freeof, e.g., formal argument of lambda.
      expr
      (let ($simp) (maxima-substitute x y expr))))

(defun mevalsumarg (expr ind low hi)
  (if (let (($prederror nil))
	(eq (mevalp `((mlessp) ,hi ,low)) t))
      0)

  (let ((gensym-ind (gensym)))
    (if (apparently-integer low) 
	(meval `(($declare) ,gensym-ind $integer)))
    (assume (list '(mgeqp) gensym-ind low))
    (if (not (eq hi '$inf))
	(assume (list '(mgeqp) hi gensym-ind)))
    (let ((msump t) (foo) (summand))
      (setq summand
            (if (and (not (atom expr)) (get (caar expr) 'mevalsumarg-macro))
		(funcall (get (caar expr) 'mevalsumarg-macro) expr)
		expr))
      (let (($simp nil))
        (setq summand ($substitute gensym-ind ind summand)))
      (setq foo (mbinding ((list gensym-ind) (list gensym-ind))
                          (resimplify (meval summand))))
      ;; At this point we do not switch off simplification to preserve
      ;; the achieved simplification of the summand (DK 02/2010).
      (let (($simp t))
	(setq foo ($substitute ind gensym-ind foo)))
      (if (not (eq hi '$inf))
	  (forget (list '(mgeqp) hi gensym-ind)))
      (forget (list '(mgeqp) gensym-ind low))
      (if (apparently-integer low)
	  (meval `(($remove) ,gensym-ind $integer)))
      foo)))

(defun apparently-integer (x)
  (or ($integerp x) ($featurep x '$integer)))

(defun do%sum (l op)
  (if (not (= (length l) 4)) (wna-err op))
  (let ((ind (cadr l)))
    (if (mquotep ind) (setq ind (cadr ind)))
    (if (not (symbolp ind))
      (merror (intl:gettext "~:M: index must be a symbol; found ~M") op ind))
    (let ((low (caddr l))
	  (hi (cadddr l)))
      (list (mevalsumarg (car l) ind low hi)
            ind (meval (caddr l)) (meval (cadddr l))))))

(defun simpsum1 (e k lo hi)
  (with-new-context (context)
    (let ((acc 0) (n) (sgn) ($prederror nil) (i (gensym)) (ex))
      (setq lo ($ratdisrep lo))
      (setq hi ($ratdisrep hi))

      (setq n ($limit (add 1 (sub hi lo))))
      (setq sgn ($sign n))

      (if (not (eq t (csign lo))) (mfuncall '$assume `((mgeqp) ,i ,lo)))
      (if (not (eq t (csign hi))) (mfuncall '$assume `((mgeqp) ,hi ,i)))

      (setq ex (subst i k e))
      (setq ex (subst i k ex)) ; Why substitute again?

      (setq acc
            (cond ((and (eq n '$inf) ($freeof i ex))
                   (setq sgn (csign ex))
                   (cond ((eq sgn '$pos) '$inf)
                         ((eq sgn '$neg) '$minf)
                         ((eq sgn '$zero) 0)
                         (t `((%sum simp) ,ex ,i ,lo ,hi))))

                  ((and (mbagp e) $listarith)
                   (simplifya
                    `((,(caar e)) ,@(mapcar #'(lambda (s) (mfuncall '$sum s k lo hi)) (margs e))) t))

                  ((or (eq sgn '$neg) (eq sgn '$zero) (eq sgn '$nz)) 0)

                  ((like ex 0) 0)

                  (($freeof i ex) (mult n ex))

                  ((and (integerp n) (eq sgn '$pos) $simpsum)
                   (dotimes (j n acc)
                     (setq acc (add acc (resimplify (subst (add j lo) i ex))))))

                  (t
                   `((%sum simp) ,(subst k i ex) ,k ,lo ,hi))))

      (setq acc (subst k i acc))

      ;; If expression is still a summation,
      ;; punt to previous simplification code.

      (if (and $simpsum (op-equalp acc '%sum))
        (let* ((args (cdr acc)) (e (first args)) (i (second args)) (i0 (third args)) (i1 (fourth args)))
          (setq acc (simpsum1-save e i i0 i1))))

      ; If the expression is no longer a %sum, resimplify.
      ; Ordering of expressions may change due to the gensym -> index substitution.
      (unless (op-equalp acc '%sum)
        (setq acc (resimplify acc)))

      acc)))

(defun simpprod1 (e k lo hi)
  (with-new-context (context)
    (let ((acc 1) (n) (sgn) ($prederror nil) (i (gensym)) (ex) (ex-mag) (realp))

      (setq lo ($ratdisrep lo))
      (setq hi ($ratdisrep hi))
      (setq n ($limit (add 1 (sub hi lo))))
      (setq sgn ($sign n))

      (if (not (eq t (csign lo))) (mfuncall '$assume `((mgeqp) ,i ,lo)))
      (if (not (eq t (csign hi))) (mfuncall '$assume `((mgeqp) ,hi ,i)))

      (setq ex (subst i k e))
      (setq ex (subst i k ex)) ; Why substitute again?

      (setq acc
            (cond
              ((like ex 1) 1)

              ((and (eq n '$inf) ($freeof i ex))
               (setq ex-mag (mfuncall '$cabs ex))
               (setq realp (mfuncall '$imagpart ex))
               (setq realp (mevalp `((mequal) 0 ,realp)))

               (cond ((eq t (mevalp `((mlessp) ,ex-mag 1))) 0)
                     ((and (eq realp t) (eq t (mevalp `((mgreaterp) ,ex 1)))) '$inf)
                     ((eq t (mevalp `((mgreaterp) ,ex-mag 1))) '$infinity)
                     ((eq t (mevalp `((mequal) 1 ,ex-mag))) '$und)
                     (t `((%product) ,e ,k ,lo ,hi))))

              ((or (eq sgn '$neg) (eq sgn '$zero) (eq sgn '$nz))
               1)

              ((and (mbagp e) $listarith)
               (simplifya
                `((,(caar e)) ,@(mapcar #'(lambda (s) (mfuncall '$product s k lo hi)) (margs e))) t))

              (($freeof i ex) (power ex n))

              ((and (integerp n) (eq sgn '$pos) $simpproduct)
               (dotimes (j n acc)
                 (setq acc (mult acc (resimplify (subst (add j lo) i ex))))))

              (t
               `((%product simp) ,(subst k i ex) ,k ,lo ,hi))))

      ;; Hmm, this is curious... don't call existing product simplifications
      ;; if index range is infinite -- what's up with that??

      (if (and $simpproduct (op-equalp acc '%product) (not (like n '$inf)))
        (let* ((args (cdr acc)) (e (first args)) (i (second args)) (i0 (third args)) (i1 (fourth args)))
          (setq acc (simpprod1-save e i i0 i1))))

      (setq acc (subst k i acc))

      ; If the expression is no longer a %product, resimplify.
      ; Ordering of expressions may change due to the gensym -> index substitution.
      (unless (op-equalp acc '%product)
        (setq acc (resimplify acc)))

      acc)))

; This function was SIMPPROD1 until the sum/product code was revised Nov 2005.
; The revised code punts back to this function since this code knows
; some simplifications not handled by the revised code. -- Robert Dodier

(defun simpprod1-save (exp i lo hi)
  (let (u)
    (cond ((not (symbolp i)) (merror (intl:gettext "product: index must be a symbol; found ~M") i))
	  ((alike1 lo hi)
	   (let ((valist (list i)))
	     (mbinding (valist (list hi))
		       (meval exp))))
	  ((eq ($sign (setq u (m- hi lo))) '$neg)
	   (cond ((eq ($sign (add2 u 1)) '$zero) 1)
		 (t (merror (intl:gettext "product: lower bound ~M greater than upper bound ~M") lo hi))))
	  ((atom exp)
	   (cond ((null (eq exp i))
		  (power* exp (list '(mplus) hi 1 (list '(mtimes) -1 lo))))
		 ((let ((lot (asksign lo)))
		    (cond ((equal lot '$zero) 0)
			  ((eq lot '$positive)
			   (m// (list '(mfactorial) hi)
				(list '(mfactorial) (list '(mplus) lo -1))))
			  ((m* (list '(mfactorial)
				     (list '(mabs) lo))
			       (cond ((member (asksign hi) '($zero $positive) :test #'eq)
				      0)
				     (t (prog1
					    (m^ -1 (m+ hi lo 1))
					  (setq hi (list '(mabs) hi)))))
			       (list '(mfactorial) hi))))))))
	  ((list '(%product simp) exp i lo hi)))))


;; multiplication of sums

(defun gensumindex ()
  (if $gensumnum
      (intern (format nil "~S~D" $genindex (incf $gensumnum)))
      (intern (format nil "~S" $genindex))))

(defun sumtimes (x y)
  (cond ((null x) y)
	((null y) x)
	((or (safe-zerop  x) (safe-zerop y)) 0)
	((or (atom x) (not (eq (caar x) '%sum))) (sumultin x y))
	((or (atom y) (not (eq (caar y) '%sum))) (sumultin y x))
	(t (let (u v i j)
	     (if (great (sum-arg x) (sum-arg y)) (setq u y v x) (setq u x v y))
	     (setq i (let ((ind (gensumindex)))
		       (setq u (subst ind (sum-index u) u)) ind))
	     (setq j (let ((ind (gensumindex)))
		       (setq v (subst ind (sum-index v) v)) ind))
	     (if (and $cauchysum (eq (sum-upper u) '$inf)
		      (eq (sum-upper v) '$inf))
		 (list '(%sum)
		       (list '(%sum)
			     (sumtimes (maxima-substitute j i (sum-arg u))
				       (maxima-substitute (m- i j) j (sum-arg v)))
			     j (sum-lower u) (m- i (sum-lower v)))
		       i (m+ (sum-lower u) (sum-lower v)) '$inf)
		 (list '(%sum)
		       (list '(%sum) (sumtimes (sum-arg u) (sum-arg v))
			     j (sum-lower v) (sum-upper v))
		       i (sum-lower u) (sum-upper u)))))))

(defun sumultin (x s)	  ; Multiplies x into a sum adjusting indices.
  (cond ((or (atom s) (not (eq (caar s) '%sum))) (m* x s))
	((free x (sum-index s))
	 (list* (car s) (sumultin x (sum-arg s)) (cddr s)))
	(t (let ((ind (gensumindex)))
	     (list* (car s)
		    (sumultin x (subst ind (sum-index s) (sum-arg s)))
		    ind
		    (cdddr s))))))

;; addition of sums

(defun sumpls (sum out)
  (prog (l)
     (if (null out) (return (cons sum nil)))
     (setq out (setq l (cons nil out)))
     a 	(if (null (cdr out)) (return (cons sum (cdr l))))
     (and (not (atom (cadr out)))
	  (consp (caadr out))
	  (eq (caar (cadr out)) '%sum)
	  (alike1 (sum-arg (cadr out)) (sum-arg sum))
	  (alike1 (sum-index (cadr out)) (sum-index sum))
	  (cond ((onediff (sum-upper (cadr out)) (sum-lower sum))
		 (setq sum (list (car sum)
				 (sum-arg sum)
				 (sum-index sum)
				 (sum-lower (cadr out))
				 (sum-upper sum)))
		 (rplacd out (cddr out))
		 (go a))
		((onediff (sum-upper sum) (sum-lower (cadr out)))
		 (setq sum (list (car sum)
				 (sum-arg sum)
				 (sum-index sum)
				 (sum-lower sum)
				 (sum-upper (cadr out))))
		 (rplacd out (cddr out))
		 (go a))))
     (setq out (cdr out))
     (go a)))

(defun onediff (x y)
  (equal 1 (m- y x)))

(defun freesum (e b a q)
  (m* e q (m- (m+ a 1) b)))

;; linear operator stuff

(defun oper-apply (e z)
  (cond ((null opers-list)
	 (let ((w (get (caar e) 'operators)))
	   (if w (funcall w e 1 z) (simpargs e z))))
	((get (caar e) (caar opers-list))
	 (let ((opers-list (cdr opers-list))
	       (fun (cdar opers-list)))
	   (funcall fun e z)))
	(t (let ((opers-list (cdr opers-list)))
	     (oper-apply e z)))))

;; Define an operator simplification, the same as antisymmetric, commutative, linear, etc.
;; Here OP = operator name, FN = function of 1 argument to carry out operator-specific simplification.
;; 1. push operator name onto OPERS
;; 2. update $OPPROPERTIES
;; 3. push operator name and glue code onto *OPERS-LIST
;; 4. declare operator name as a feature, so declare(..., <op>) is recognized

(defmfun $define_opproperty (op fn)
  (unless (symbolp op)
    (merror "define_opproperty: first argument must be a symbol; found: ~M" op))
  (unless (or (symbolp fn) (and (consp fn) (eq (caar fn) 'lambda)))
    (merror "define_opproperty: second argument must be a symbol or lambda expression; found: ~M" fn))
  (push op opers)
  (setq $opproperties (cons '(mlist simp) (reverse opers)))
  (let
    ((fn-glue (coerce (if (symbolp fn)
                        `(lambda (e z)
                           (declare (ignorable z))
                           (if (or (fboundp ',fn) (mget ',fn 'mexpr))
                             (let ((e1 (let ($simp) (mfuncall ',fn e))))
                               (if ($mapatom e1) e1 (oper-apply e1 nil)))
                             (list '(,fn) (let ((*opers-list (cdr *opers-list))) (oper-apply e z)))))
                        `(lambda (e z)
                           (declare (ignore z))
                           (let ((e1 (let ($simp) (mfuncall ',fn e))))
                             (if ($mapatom e1) e1 (oper-apply e1 nil)))))
                      'function)))
    (push `(,op . ,fn-glue) *opers-list))
  (mfuncall '$declare op '$feature))

(defun linearize1 (e z)		; z = t means args already simplified.
  (linearize2 (cons (car e) (mapcar #'(lambda (q) (simpcheck q z)) (cdr e)))
	      nil))

(defun opident (op)
  (cond ((eq op 'mplus) 0)
	((eq op 'mtimes) 1)))

(defun rem-const (e)			;removes constantp stuff
  (do ((l (cdr e) (cdr l))
       (a (list (opident (caar e))))
       (b (list (opident (caar e)))))
      ((null l)
       (cons (simplifya (cons (list (caar e)) a) nil)
	     (simplifya (cons (list (caar e)) b) nil)))
    (if ($constantp (car l))
	(setq a (cons (car l) a))
	(setq b (cons (car l) b)))))

(defun linearize2 (e times)
  (cond ((linearconst e))
	((atom (cadr e)) (oper-apply e t))
	((eq (caar (cadr e)) 'mplus)
	 (addn (mapcar #'(lambda (q)
			   (linearize2 (list* (car e) q (cddr e)) nil))
		       (cdr (cadr e)))
	       t))
	((and (eq (caar (cadr e)) 'mtimes) (null times))
	 (let ((z (if (and (cddr e)
			   (or (atom (caddr e))
			       ($subvarp (caddr e))))
		      (partition (cadr e) (caddr e) 1)
		      (rem-const (cadr e))))
	       (w))
	   (setq w (linearize2 (list* (car e)
				      (simplifya (cdr z) t)
				      (cddr e))
			       t))
	   (linearize3 w e (car z))))
	(t (oper-apply e t))))

(defun linearconst (e)
  (if (or (mnump (cadr e))
	  (constant (cadr e))
	  (and (cddr e)
	       (or (atom (caddr e)) (member 'array (cdar (caddr e)) :test #'eq))
	       (free (cadr e) (caddr e))))
      (if (or (zerop1 (cadr e))
	      (and (member (caar e) '(%sum %integrate) :test #'eq)
		   (= (length e) 5)
		   (or (eq (cadddr e) '$minf)
		       (member (car (cddddr e)) '($inf $infinity) :test #'eq))
		   (eq ($asksign (cadr e)) '$zero)))
	  0
	  (let ((w (oper-apply (list* (car e) 1 (cddr e)) t)))
	    (linearize3 w e (cadr e))))))

(defun linearize3 (w e x)
  (let (w1)
    (if (and (member w '($inf $minf $infinity) :test #'eq) (safe-zerop x))
	(merror (intl:gettext "LINEARIZE3: undefined form 0*inf: ~M") e))
    (setq w (mul2 (simplifya x t) w))
    (cond ((or (atom w) (getl (caar w) '($outative $linear))) (setq w1 1))
	  ((eq (caar w) 'mtimes)
	   (setq w1 (cons '(mtimes) nil))
	   (do ((w2 (cdr w) (cdr w2)))
	       ((null w2) (setq w1 (nreverse w1)))
	     (if (or (atom (car w2))
		     (not (getl (caaar w2) '($outative $linear))))
		 (setq w1 (cons (car w2) w1)))))
	  (t (setq w1 w)))
    (if (and (not (atom w1)) (or (among '$inf w1) (among '$minf w1)))
	(infsimp w)
	w)))

(setq opers (cons '$additive opers)
      *opers-list (cons '($additive . additive) *opers-list))

(defun rem-opers-p (p)
  (cond ((eq (caar opers-list) p)
	 (setq opers-list (cdr p)))
	((do ((l opers-list (cdr l)))
	     ((null l))
	   (if (eq (caar (cdr l)) p)
	       (return (rplacd l (cddr l))))))))

(defun additive (e z)
  (cond ((get (caar e) '$outative)  ; Really a linearize!
         (setq opers-list (copy-list opers-list))
         (rem-opers-p '$outative)
         (linearize1 e z))
        ((mplusp (cadr e))
         (addn (mapcar #'(lambda (q)
                           (let ((opers-list *opers-list))
                             (oper-apply (list* (car e) q (cddr e)) z)))
                       (cdr (cadr e)))
               z))
        (t (oper-apply e z))))

(setq opers (cons '$multiplicative opers)
      *opers-list (cons '($multiplicative . multiplicative) *opers-list))

(defun multiplicative (e z)
  (cond ((mtimesp (cadr e))
         (muln (mapcar #'(lambda (q)
                           (let ((opers-list *opers-list))
                             (oper-apply (list* (car e) q (cddr e)) z)))
                       (cdr (cadr e)))
               z))
        (t (oper-apply e z))))

(setq opers (cons '$outative opers)
      *opers-list (cons '($outative . outative) *opers-list))

(defun outative (e z)
  (setq e (cons (car e) (mapcar #'(lambda (q) (simpcheck q z)) (cdr e))))
  (cond ((get (caar e) '$additive)
	 (setq opers-list (copy-list opers-list ))
	 (rem-opers-p '$additive)
	 (linearize1 e t))
	((linearconst e))
	((mtimesp (cadr e))
	 (let ((u (if (and (cddr e)
			   (or (atom (caddr e))
			       ($subvarp (caddr e))))
		      (partition (cadr e) (caddr e) 1)
		      (rem-const (cadr e))))
	       (w))
	   (setq w (oper-apply (list* (car e)
				      (simplifya (cdr u) t)
				      (cddr e))
			       t))
	   (linearize3 w e (car u))))
	(t (oper-apply e t))))

(defprop %sum t $outative)
(defprop %sum t opers)
(defprop %integrate t $outative)
(defprop %integrate t opers)
(defprop %limit t $outative)
(defprop %limit t opers)

(setq opers (cons '$evenfun opers)
      *opers-list (cons '($evenfun . evenfun) *opers-list))

(setq opers (cons '$oddfun opers)
      *opers-list (cons '($oddfun . oddfun) *opers-list))

(defun evenfun (e z)
  (if (or (null (cdr e)) (cddr e))
      (merror (intl:gettext "Function declared 'even' takes exactly one argument; found ~M") e))
  (let ((arg (simpcheck (cadr e) z)))
    (oper-apply (list (car e) (if (mminusp arg) (neg arg) arg)) t)))

(defun oddfun (e z)
  (if (or (null (cdr e)) (cddr e))
      (merror (intl:gettext "Function declared 'odd' takes exactly one argument; found ~M") e))
  (let ((arg (simpcheck (cadr e) z)))
    (if (mminusp arg) (neg (oper-apply (list (car e) (neg arg)) t))
	(oper-apply (list (car e) arg) t))))

(setq opers (cons '$commutative opers)
      *opers-list (cons '($commutative . commutative1) *opers-list))

(setq opers (cons '$symmetric opers)
      *opers-list (cons '($symmetric . commutative1) *opers-list))

(defun commutative1 (e z)
  (oper-apply (cons (car e)
		    (reverse
		     (sort (mapcar #'(lambda (q) (simpcheck q z))
				   (cdr e))
			   'great)))
	      t))

(setq opers (cons '$antisymmetric opers)
      *opers-list (cons '($antisymmetric . antisym) *opers-list))

(defun antisym (e z)
  (when (and $dotscrules (mnctimesp e))
    (let ($dotexptsimp)
      (setq e (simpnct e 1 nil))))
  (if ($atom e) e (antisym1 e z)))

(defun antisym1 (e z)
  (let ((antisym-sign nil)
	(l (mapcar #'(lambda (q) (simpcheck q z)) (cdr e))))
    (when (or (not (eq (caar e) 'mnctimes)) (freel l 'mnctimes))
      (multiple-value-setq (l antisym-sign) (bbsort1 l)))
    (cond ((equal l 0) 0)
	  ((prog1
	       (null antisym-sign)
	     (setq e (oper-apply (cons (car e) l) t)))
	   e)
	  (t (neg e)))))

(defun bbsort1 (l)
  (prog (sl sl1 antisym-sign)
     (if (or (null l) (null (cdr l))) (return (values l antisym-sign))
	 (setq sl (list nil (car l))))
     loop (setq l (cdr l))
     (if (null l) (return (values (nreverse (cdr sl)) antisym-sign)))
     (setq sl1 sl)
     loop1(cond ((null (cdr sl1)) (rplacd sl1 (cons (car l) nil)))
		((alike1 (car l) (cadr sl1)) (return (values 0 nil)))
		((great (car l) (cadr sl1)) (rplacd sl1 (cons (car l) (cdr sl1))))
		(t (setq antisym-sign (not antisym-sign) sl1 (cdr sl1)) (go loop1)))
     (go loop)))

(setq opers (cons '$nary opers)
      *opers-list (cons '($nary . nary1) *opers-list))

(defun nary1 (e z)
  (oper-apply (nary2 e z) z))

(defun nary2 (e z)
  (do
    ((l (cdr e) (cdr l)) (ans) (some-change))

    ((null l)
     (if some-change
       (nary2 (cons (car e) (nreverse ans)) z)
       (simpargs e z)))

    (setq
      ans (if (and (not (atom (car l))) (eq (caaar l) (caar e)))
            (progn
              (setq some-change t)
              (nconc (reverse (cdar l)) ans))
            (cons (car l) ans)))))

(setq opers (cons '$lassociative opers)
      *opers-list (cons '($lassociative . lassociative) *opers-list))

(defun lassociative (e z)
  (let*
    ((ans0 (oper-apply (cons (car e) (total-nary e)) z))
     (ans (if (consp ans0) (cdr ans0))))
    (cond ((or (null (cddr ans)) (not (eq (caar ans0) (caar e)))) ans0)
          ((do ((newans (list (car e) (car ans) (cadr ans))
                        (list (car e) newans (car ans)))
                (ans (cddr ans) (cdr ans)))
               ((null ans) newans))))))

(setq opers (cons '$rassociative opers)
      *opers-list (cons '($rassociative . rassociative) *opers-list))

(defun rassociative (e z)
  (let*
    ((ans0 (oper-apply (cons (car e) (total-nary e)) z))
     (ans (if (consp ans0) (cdr ans0))))
    (cond ((or (null (cddr ans)) (not (eq (caar ans0) (caar e)))) ans0)
	  (t (setq ans (nreverse ans))
	     (do ((newans (list (car e) (cadr ans) (car ans))
			  (list (car e) (car ans) newans))
		  (ans (cddr ans) (cdr ans)))
		 ((null ans) newans))))))

(defun total-nary (e)
  (do ((l (cdr e) (cdr l)) (ans))
      ((null l) (nreverse ans))
    (setq ans (if (and (not (atom (car l))) (eq (caaar l) (caar e)))
		  (nconc (reverse (total-nary (car l))) ans)
		  (cons (car l) ans)))))
