[Maxima-bugs] [ maxima-Bugs-910271 ] macsyma-read-string /FIX

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Bugs item #910271, was opened at 2004-03-05 01:36
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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=910271&group_id=4933

Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: macsyma-read-string /FIX

Initial Comment:
Macsyma-read-string currently doesn't work in GCL 5.9.0
(problem with vector-push-extend) and has no error 
handling.  Here's a fixed version with good error handling.

Example:

  (meval (macsyma-read-string "diff(x^2,x)"))
    => ((MTIMES SIMP) 2 |$x|)

;;; Copyright 2004 by Stavros Macrakis
;;; Licensed under your choice of the GPL or the 
modified BSD license

;;; Parse a string as a Maxima expression
;;; Return the parsed form
;;; If there's an error, it returns the symbol parse-error; 
the ;;; second return value is then the error string.

;;; Usage examples:
;;;
;;; (macsyma-read-string "1/+3*x") =>
;;;   ((MQUOTIENT) 1 ((MPLUS) ((MTIMES) 3 |$x|)))
;;;   NIL
;;;
;;; Note that this is simply parsed -- no simplification.
;;; The simplified form is 
;;; ((MTIMES SIMP) ((RAT SIMP) 1 3) ((MEXPT SIMP) 
|$x| -1))
;;;
;;; (macsyma-read-string "1.2.3") =>
;;;   NIL
;;;   "Incorrect syntax: 0.29999999999999999 is not an 
infix operator"

(defun macsyma-read-string (str)
  (with-input-from-string
   (stream (concatenate 'string str "$"))
   (let* ((*standard-input* stream)
          (*standard-output* (make-string-output-
stream))
            ;; catches error strings
          (expr
           (catch 'macsyma-quit
             (list (caddr (mread stream)))))
          (error-string (get-output-stream-string 
*standard-output*)))
     (values
      (if (atom expr) 'parse-error (car expr))
      (cond ((not (equal error-string "")) error-string)
            ((tyi stream) "Excess characters in input string")
            ((not (listp expr)) "Unknown read error")
            (t nil))))))

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