[Emacs-diffs] Changes to emacs/lisp/calc/calc-math.el,v

[Jay Belanger]

CVSROOT:        /cvsroot/emacs
Module name:    emacs
Changes by:     Jay Belanger <jpb>      07/10/01 03:15:01

Index: calc-math.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/calc/calc-math.el,v
retrieving revision 1.27
retrieving revision 1.28
diff -u -b -r1.27 -r1.28
--- calc-math.el        1 Oct 2007 02:53:29 -0000       1.27
+++ calc-math.el        1 Oct 2007 03:15:01 -0000       1.28
@@ -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