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(math-emacs-precision, math-largest-emacs-expt)

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(math-smallest-emacs-expt): New variables.
(math-use-emacs-fn): New function.
(math-exp-raw): Evaluate with `math-use-emacs-fn', when appropriate.
This commit is contained in:
Jay Belanger 2007-07-22 03:34:39 +00:00
parent a226e0ef9c
commit 178b8bafc2
2 changed files with 75 additions and 0 deletions
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9
lisp/ChangeLog
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@ -1,3 +1,12 @@
2007-07-21 Jay Belanger <jay.p.belanger@gmail.com>
* calc/calc-math.el (math-emacs-precision)
(math-largest-emacs-expt, math-smallest-emacs-expt):
New variables.
(math-use-emacs-fn): New function.
(math-exp-raw): Evaluate with `math-use-emacs-fn', when
appropriate.
2007-07-21 Thien-Thi Nguyen <ttn@gnuvola.org>
* image-dired.el (image-dired-sane-db-file): New func.

66
lisp/calc/calc-math.el
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@ -32,6 +32,71 @@
(require 'calc-ext)
(require 'calc-macs)
;;; Find out how many 9s in 9.9999... will give distinct Emacs floats,
;;; then back off by one.
(defvar math-emacs-precision
(let* ((n 1)
(x 9)
(xx (+ x (* 9 (expt 10 (- n))))))
(while (/= x xx)
(progn
(setq n (1+ n))
(setq x xx)
(setq xx (+ x (* 9 (expt 10 (- n)))))))
(1- n))
"The number of digits in an Emacs float.")
;;; Find the largest power of 10 which is an Emacs float,
;;; then back off by one so that any float d.dddd...eN
;;; is an Emacs float, for acceptable d.dddd....
(defvar math-largest-emacs-expt
(let ((x 1))
(while (condition-case nil
(expt 10.0 x)
(error nil))
(setq x (* 2 x)))
(setq x (/ x 2))
(while (condition-case nil
(expt 10.0 x)
(error nil))
(setq x (1+ x)))
(- x 2))
"The largest exponent which Calc will convert to an Emacs float.")
(defvar math-smallest-emacs-expt
(let ((x -1))
(while (condition-case nil
(expt 10.0 x)
(error nil))
(setq x (* 2 x)))
(setq x (/ x 2))
(while (condition-case nil
(expt 10.0 x)
(error nil))
(setq x (1- x)))
(+ x 2))
"The smallest exponent which Calc will convert to an Emacs float.")
(defun math-use-emacs-fn (fn x)
"Use the native Emacs function FN to evaluate the Calc number X.
If this can't be done, return NIL."
(and
(<= calc-internal-prec math-emacs-precision)
(math-realp x)
(let* ((fx (math-float x))
(xpon (+ (nth 2 x) (1- (math-numdigs (nth 1 x))))))
(and (<= math-smallest-emacs-expt xpon)
(<= xpon math-largest-emacs-expt)
(condition-case nil
(math-read-number
(number-to-string
(funcall fn
(string-to-number (math-format-number (math-float x))))))
(error nil))))))
(defun calc-sqrt (arg)
(interactive "P")
(calc-slow-wrapper
@ -1403,6 +1468,7 @@
(list 'polar
(math-exp-raw (nth 1 xc))
(math-from-radians (nth 2 xc)))))
((math-use-emacs-fn 'exp x))
((or (math-lessp-float '(float 5 -1) x)
(math-lessp-float x '(float -5 -1)))
(if (math-lessp-float '(float 921035 1) x)