Commit c28ddc17 authored by rtoy's avatar rtoy
Browse files

o Add new condition type for exceeding the intexp maximum exponent. 

o Instead of a continuable error, use a restart to allow the user to
  continue the calculation with the option of updating the limit to
  the new power.

Should we also increase the initial limit to something larger?  Should
we just eliminate this altogether?  Or maybe allow the
*intexp-maximum-exponent* to be nil to mean no limit at all?
parent d76f4bf9

code/irrat.lisp

+20 −4
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
;;; Carnegie Mellon University, and has been placed in the public domain.

;;;

(ext:file-comment

  "$Header: /Volumes/share2/src/cmucl/cvs2git/cvsroot/src/code/irrat.lisp,v 1.56 2008/10/08 17:03:07 rtoy Exp $")

  "$Header: /Volumes/share2/src/cmucl/cvs2git/cvsroot/src/code/irrat.lisp,v 1.57 2008/10/22 14:02:27 rtoy Exp $")

;;;

;;; **********************************************************************

;;;
@@ -287,6 +287,14 @@ 


(defparameter *intexp-maximum-exponent* 10000)



(define-condition intexp-limit-error (error)

  ((base :initarg :base :reader intexp-base)

   (power :initarg :power :reader intexp-power))

  (:report (lambda (condition stream)

	     (format stream "The absolute value of ~S exceeds limit ~S."

		     (intexp-power condition)

		     *intexp-maximum-exponent*))))



;;; This function precisely calculates base raised to an integral power.  It

;;; separates the cases by the sign of power, for efficiency reasons, as powers

;;; can be calculated more efficiently if power is a positive integer.  Values
@@ -300,9 +308,17 @@ 
    (return-from intexp base))

  

  (when (> (abs power) *intexp-maximum-exponent*)

    (cerror "Continue with calculation."

	    "The absolute value of ~S exceeds ~S."

	    power '*intexp-maximum-exponent* base power))

    ;; Allow user the option to continue with calculation, possibly

    ;; increasing the limit to the given power.

    (restart-case

	(error 'intexp-limit-error

	       :base base

	       :power power)

      (continue ()

	:report "Continue with calculation")

      (new-limit ()

	:report "Continue with calculation, update limit"

	(setq *intexp-maximum-exponent* power))))

  (cond ((minusp power)

	 (/ (intexp base (- power))))

	((eql base 2)