Changeset 4370

Timestamp:

2016-06-06T19:28:40-07:00 (9 years ago)

Author:

Marek Rychlik

Message:

* empty log message *

File:

• branches/f4grobner/polynomial.lisp (modified) (1 diff)

branches/f4grobner/polynomial.lisp

@@ -622 +622 @@
   (cons +list-marker+ (mapcar #'(lambda (p) (->sexp p vars)) (cdr self))))
 
-
-(defvar *coefficient-class* 'integer-ring
-  "The default class in which coefficients are created from
-NUMBER tokens.")
-
-(defun poly-eval (expr vars order &optional (coefficient-class *coefficient-class*))
-  "Evaluate Lisp form EXPR to a polynomial or a list of polynomials in
-variables VARS. Return the resulting polynomial or list of
-polynomials.  Standard arithmetical operators in form EXPR are
-replaced with their analogues in the ring of polynomials, and the
-resulting expression is evaluated, resulting in a polynomial or a list
-of polynomials in internal form. A similar operation in another computer
-algebra system could be called 'expand' or so."
-  (labels ((p-eval (p) (poly-eval p vars order))
-           (p-eval-list (plist) (mapcar #'p-eval plist)))
-    (cond 
-      ((eq expr 0) 
-       (make-instance 'poly :dimension (length vars)))
-      ((member expr vars :test #'equalp)
-       (let ((pos (position expr vars :test #'equalp)))
-         (make-poly-variable (length vars) pos)))
-      ((numberp expr)
-       (make-poly-constant (length vars) (make-instance coefficient-class :value expr)))
-      ((eq (car expr) +list-marker+)
-       (cons +list-marker+ (p-eval-list (cdr expr))))
-      (t
-       (case (car expr)
-         (+ (reduce #'add (p-eval-list (cdr expr))))
-         (- (apply #'subtract (p-eval-list (cdr expr))))
-         (*
-          (if (endp (cddr expr))        ;unary
-              (p-eval (cadr expr))
-              (apply #'multiply (p-eval-list (cdr expr)))))
-         (/ 
-          ;; A polynomial can be divided by a scalar
-          (cond 
-            ((endp (cddr expr))
-             ;; A special case (/ ?), the inverse
-             (divide (cadr expr)))
-            (t
-             (let ((num (p-eval (cadr expr)))
-                   (denom-inverse (apply #'divide (mapcar #'p-eval (cddr expr)))))
-               (multiply denom-inverse num)))))
-         (expt
-          (cond
-            ((member (cadr expr) vars :test #'equalp)
-             ;;Special handling of (expt var pow)
-             (let ((pos (position (cadr expr) vars :test #'equalp)))
-               (make-poly-variable (length vars) pos (caddr expr))))
-            ((not (and (integerp (caddr expr)) (plusp (caddr expr))))
-             ;; Negative power means division in coefficient ring
-             ;; Non-integer power means non-polynomial coefficient
-             expr)
-            (t (universal-expt (p-eval (cadr expr)) (caddr expr)))))
-         (otherwise
-          (error "Cannot evaluate as polynomial: ~A" expr)))))))
-
 (defmethod make-zero-for ((self poly))
   (make-instance 'poly :dimension (poly-dimension self)))