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calc-math.el (math-largest-emacs-expt): Handle the cases when expt

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doesn't give range errors.
This commit is contained in:
Jay Belanger 2007-10-01 03:18:00 +00:00
parent f1640784ad
commit 86e405cfcb
2 changed files with 37 additions and 11 deletions
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10
lisp/ChangeLog
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@ -1,3 +1,13 @@
2007-10-01 Jay Belanger <jay.p.belanger@gmail.com>
* calc/calc-math.el (math-largest-emacs-expt): Handle the cases
when `expt' doesn't give range errors.
2007-10-01 Markus Triska <markus.triska@gmx.at>
* calc/calc-math.el (math-smallest-emacs-expt): Make the
computation more robust.
2007-09-30 David Kastrup <dak@gnu.org>
* startup.el (argv): Alias for `command-line-args-left' to use as

38
lisp/calc/calc-math.el
View file

@ -53,17 +53,33 @@
;;; 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))
(let ((x 1)
(pow 1e2))
;; The following loop is for efficiency; it should stop when
;; 10^(2x) is too large. This could be indicated by a range
;; error when computing 10^(2x), an infinite value for 10^(2x),
;; or (!) a zero value for 10^(2x).
(while (and
pow
(< pow 1.0e+INF)
(> pow 0.0))
(setq x (* 2 x))
(setq pow (condition-case nil
(expt 10.0 (* 2 x))
(error nil))))
;; The following loop should stop when 10^(x+1) is too large.
(setq pow (condition-case nil
(expt 10.0 (1+ x))
(error nil)))
(while (and
pow
(< pow 1.0e+INF)
(> pow 0.0))
(setq x (1+ x))
(setq pow (condition-case nil
(expt 10.0 (1+ x))
(error nil))))
(1- x))
"The largest exponent which Calc will convert to an Emacs float.")
(defvar math-smallest-emacs-expt