;;; -*-  Mode: Lisp; Package: Maxima; Syntax: Common-Lisp; Base: 10 -*- ;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;     The data in this file contains enhancments.                    ;;;;;
;;;                                                                    ;;;;;
;;;  Copyright (c) 1984,1987 by William Schelter,University of Texas   ;;;;;
;;;     All rights reserved                                            ;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; SUBLIS: A Macsyma flavor of Lisp's SUBLIS...
;;;
;;; ** (c) Copyright 1980 Massachusetts Institute of Technology **

(in-package "MAXIMA")
(macsyma-module sublis)

(DEFMVAR $SUBLIS_APPLY_LAMBDA T 
  "a flag which controls whether LAMBDA's substituted are applied in
   simplification after the SUBLIS or whether you have to do an
   EV to get things to apply. A value of TRUE means perform the application.")

    ; The EXPR stuff here should eventually be flushed.
(declare-top #-cl (*EXPR $LISTP $RAT $RATP $RATDISREP GETOPR) 
	 (SPECIAL *MSUBLIS-MARKER*))

;;; SUBLIS([sym1=form1,sym2=form2,...],expression)$
;;;
;;;  This should change all occurrences of sym1 in expression to form1,
;;;  all occurrences of sym2 to form2, etc. The replacement is done in
;;;  parallel, so having occurrences of sym1 in form2, etc. will have
;;;  the `desired' (non-interfering) effect.

(DEFMFUN $SUBLIS (SUBSTITUTIONS FORM)
  (COND
   (($LISTP SUBSTITUTIONS)
    (DO ((L  (CDR SUBSTITUTIONS) (CDR L))
	 (NL ())
	 (TEMP))
	((NULL L) (SETQ SUBSTITUTIONS NL))
      (SETQ TEMP (CAR L))
      (COND ((AND (NOT (ATOM TEMP))
		  (NOT (ATOM (CAR TEMP)))
		  (EQ (CAAR TEMP) 'MEQUAL)
		  (SYMBOLP (CAR (POP TEMP))))
	     (PUSH (CONS (POP TEMP) (POP TEMP)) NL))
	    (T (MERROR "Usage is SUBLIS([sym1=form1,...],expression)")))))
   (T
    (MERROR "Usage is SUBLIS([sym1=form1,...],expression)")))
  (MSUBLIS SUBSTITUTIONS FORM))

(DEFUN MSUBLIS (S Y)
  (DECLARE (SPECIAL S))
  (LET ((*MSUBLIS-MARKER* (COPY-SYMBOL '*MSUBLIS-MARKER* NIL)))
    (MSUBLIS-SETUP)
    (UNWIND-PROTECT (MSUBLIS-SUBST Y T) (MSUBLIS-UNSETUP))))

(DEFUN MSUBLIS-SETUP ()
  (DECLARE (SPECIAL S))
       (DO ((X S (CDR X)) (TEMP) (TEMP1)) ((NULL X))
	(COND ((NOT (SYMBOLP (SETQ TEMP (CAAR X))))
	       (MERROR "SUBLIS: Bad 1st arg")))
	(SETPLIST TEMP (LIST* *MSUBLIS-MARKER* (CDAR X) (SYMBOL-PLIST TEMP)))
	(COND ((NOT (EQ TEMP (SETQ TEMP1 (GETOPR TEMP))))
	       (SETPLIST TEMP1 (LIST* *MSUBLIS-MARKER* (CDAR X) (SYMBOL-PLIST TEMP1)))
	       (PUSH (NCONS TEMP1) S))))) ; Remember extra cleanup

(DEFUN MSUBLIS-UNSETUP ()
  (DECLARE (SPECIAL S))
       (DO ((X S (CDR X))) ((NULL X)) (REMPROP (CAAR X) *MSUBLIS-MARKER*)))

(DEFUN MSUBLIS-SUBST (FORM FLAG)
       (COND ((ATOM FORM)
	      (COND ((AND (NULL FORM) (NOT FLAG)) NIL) ;preserve trailing NILs
		    ((SYMBOLP FORM)
		     (COND ((EQ (CAR (SYMBOL-PLIST FORM)) *MSUBLIS-MARKER*)
			    (CADR (SYMBOL-PLIST FORM)))
			   (T FORM)))
		    (T FORM)))
	     (FLAG
	      (COND (($RATP FORM)
		     (LET* ((DISREP ($RATDISREP FORM))
			    (SUB    (MSUBLIS-SUBST DISREP T)))
			   (COND ((EQ DISREP SUB) FORM)
				 (T ($RAT SUB)))))
		    ((ATOM (CAR FORM))
		     (MERROR
		       "SUBLIS: Illegal object in expression being substituted for."))
		    (T
		     (LET ((CDR-VALUE (MSUBLIS-SUBST (CDR FORM) NIL))
			   (CAAR-VALUE (MSUBLIS-SUBST (CAAR FORM) T)))
			  (COND ((AND (EQ CDR-VALUE (CDR FORM))
				      (EQ (CAAR FORM) CAAR-VALUE))
				 FORM)
				((AND $SUBLIS_APPLY_LAMBDA
				      (EQ (CAAR FORM) 'MQAPPLY)
				      (EQ CAAR-VALUE 'MQAPPLY)
				      (ATOM (CADR FORM))
				      (NOT (ATOM (CAR CDR-VALUE)))
				      (EQ (CAAR (CAR CDR-VALUE)) 'LAMBDA))
				 (CONS (CONS (CAR CDR-VALUE)
					     (COND ((MEMQ 'array (CAR FORM))
						    '(ARRAY))
						   (T NIL)))
				       (CDR CDR-VALUE)))
				((AND (NOT (ATOM CAAR-VALUE))
				      (OR (NOT (OR (EQ (CAR CAAR-VALUE) 'LAMBDA)
						   (EQ (CAAR CAAR-VALUE) 'LAMBDA)))
					  (NOT $SUBLIS_APPLY_LAMBDA)))
				 (LIST* (CONS 'MQAPPLY
					      (COND ((MEMQ 'array (CAR FORM))
						     '(ARRAY))
						    (T NIL)))
					CAAR-VALUE
					CDR-VALUE))
				(T (CONS (CONS CAAR-VALUE
					       (COND ((MEMQ 'array (CAR FORM))
						      '(ARRAY))
						     (T NIL)))
					 CDR-VALUE)))))))
	     (T
	      (LET ((CAR-VALUE (MSUBLIS-SUBST (CAR FORM) T))
		    (CDR-VALUE (MSUBLIS-SUBST (CDR FORM) NIL)))
		   (COND ((AND (EQ (CAR FORM) CAR-VALUE)
			       (EQ (CDR FORM) CDR-VALUE))
			  FORM)
			 (T
			  (CONS CAR-VALUE CDR-VALUE)))))))