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Index: src/plot.lisp
===================================================================
RCS file: /cvsroot/maxima/maxima/src/plot.lisp,v
retrieving revision 1.24
diff -u -r1.24 plot.lisp
--- src/plot.lisp	13 May 2003 03:46:04 -0000	1.24
+++ src/plot.lisp	15 May 2003 03:30:31 -0000
@@ -449,9 +449,21 @@
 	       ;(na (gensym "TMPF"))
 		)
 	   (coerce `(lambda ,(cdr vars)
-		      (declare (special ,@(cdr vars)))
-		      (let (($ratprint nil))
-			($float ($realpart (meval* ',expr)))))
+		      (declare (special ,@(cdr vars) errorsw))
+		      (let (($ratprint nil)
+			    (errorsw t))
+			;; Catch any errors from evaluating the
+			;; function.  We're assuming that if an error
+			;; is caught, the result is not a number.  We
+			;; also assume that for such errors, it's
+			;; because the function is not defined there,
+			;; not because of some other maxima error.
+			(let ((result
+			       (catch 'errorsw
+				 ($float ($realpart (meval* ',expr))))))
+			  (unless (numberp result)
+			    (format t "fun returned ~A~%" result))
+			  result)))
 		   'function)))))
 
 (defmacro zval (points verts i) `(aref ,points (f+ 2 (f* 3 (aref ,verts ,i)))))
@@ -687,10 +699,15 @@
 ;; are not monotonic.
 (defun slow-oscillation-p (f0 f1 f2 f3 f4)
   (flet ((sign-change (x y z)
-	   (if (or (and (> y x) (> y z))
-		   (and (< y x) (< y z)))
-	       1
-	       0)))
+	   (cond ((not (and (numberp x) (numberp y) (numberp z)))
+		  ;; Something is not a number.  Assume the
+		  ;; oscillation is not slow.
+		  2)
+		 ((or (and (> y x) (> y z))
+		      (and (< y x) (< y z)))
+		  1)
+		 (t
+		  0))))
     (<= (+ (sign-change f0 f1 f2)
 	   (sign-change f1 f2 f3)
 	   (sign-change f2 f3 f4))
@@ -702,24 +719,28 @@
 ;;
 ;; 
 (defun smooth-enough-p (f-a f-a1 f-b f-b1 f-c eps)
-  (let ((quad (/ (+ f-a
-		    (* -5 f-a1)
-		    (* 9 f-b)
-		    (* -7 f-b1)
-		    (* 2 f-c))
-		 24))
-	(quad-b (/ (+ (* 5 f-b)
-		      (* 8 f-b1)
-		      (- f-c))
-		   12)))
-    ;; According to the Yacas source code, quad is the Simpson
-    ;; quadrature for the (fb,fb1) subinterval (using points b,b1,c),
-    ;; subtracted from the 4-point Newton-Cotes quadrature for the
-    ;; (fb,fb1) subinterval (using points a, a1, b, b1.
-    ;;
-    ;; quad-b is the Simpson quadrature for the (fb,f1) subinterval.
-    (<= (abs quad)
-	(* eps (- quad-b (min f-a f-a1 f-b f-b1 f-c))))))
+  (cond ((every #'numberp (list f-a f-a1 f-b f-b1 f-c))
+	 (let ((quad (/ (+ f-a
+			   (* -5 f-a1)
+			   (* 9 f-b)
+			   (* -7 f-b1)
+			   (* 2 f-c))
+			24))
+	       (quad-b (/ (+ (* 5 f-b)
+			     (* 8 f-b1)
+			     (- f-c))
+			  12)))
+	   ;; According to the Yacas source code, quad is the Simpson
+	   ;; quadrature for the (fb,fb1) subinterval (using points b,b1,c),
+	   ;; subtracted from the 4-point Newton-Cotes quadrature for the
+	   ;; (fb,fb1) subinterval (using points a, a1, b, b1.
+	   ;;
+	   ;; quad-b is the Simpson quadrature for the (fb,f1) subinterval.
+	   (<= (abs quad)
+	       (* eps (- quad-b (min f-a f-a1 f-b f-b1 f-c))))))
+	(t
+	 ;; Something is not a number, so assume it's not smooth enough.
+	 nil)))
 		    
     
 (defun adaptive-plot (f a b c f-a f-b f-c depth eps)
@@ -774,7 +795,8 @@
 	(do ((x result (cddr x))
 	     (y (cdr result) (cddr y)))
 	    ((null y))
-	  (unless (<= ymin (car y) ymax)
+	  (unless (and (numberp (car y))
+		       (<= ymin (car y) ymax))
 	    (setf (car x) 'moveto)
 	    (setf (car y) 'moveto)))
 	(cons '(mlist) result)))))
@@ -837,9 +859,9 @@
 
 (defvar $openmath_plot_command "omplotdata")
 
-(defun $plot2d(fun &optional range &rest options &aux ($numer t) $display2d
-                          (i 0) plot-format file plot-name
-			  ($plot_options $plot_options))
+(defun $plot2d (fun &optional range &rest options &aux ($numer t) $display2d
+		    (i 0) plot-format file plot-name
+		    ($plot_options $plot_options))
   (dolist (v options) ($set_plot_option v))
   (or ($listp fun ) (setf fun `((mlist) ,fun)))
   (cond ((eq (cadr fun) '$parametric)
@@ -854,9 +876,10 @@
   (with-open-file (st  file :direction :output)  
     (dolist (v (cdr fun))
 	    (incf i)
-	    (setq plot-name 		       (let ((string (coerce (mstring v) 'string)))
-			 (cond ((< (length string) 9) string)
-			       (t (format nil "Fun~a" i)))))
+	    (setq plot-name
+		  (let ((string (coerce (mstring v) 'string)))
+		    (cond ((< (length string) 9) string)
+			  (t (format nil "Fun~a" i)))))
 	(case plot-format
 	      ($xgraph
 	       (format st "~%~% \"~a\"~%" plot-name))
@@ -866,9 +889,12 @@
       (sloop for (v w) on (cdr (draw2d v range )) by 'cddr
 	 do
 	 (cond ((eq v 'moveto)
-		(unless (equal plot-format '$gnuplot)
-		    (format st "move ")))
-	       (t  (format st "~,3f ~,3f ~%" v w))))))
+		(cond ((equal plot-format '$gnuplot)
+		       ;; A blank line means a discontinuity
+		       (format st "~%"))
+		      (t
+		       (format st "move "))))
+	       (t  (format st "~g ~g ~%" v w))))))
   (case plot-format
 	($gnuplot 
 	 ($system (concatenate 'string *maxima-plotdir* "/" $gnuplot_command) " -plot2d maxout.gnuplot -title '" plot-name "'"))