[Cmucl-cvs] [git] CMU Common Lisp branch master updated. snapshot-2014-11-23-g37d383a

[Raymond Toy]

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- Log -----------------------------------------------------------------
commit 37d383ae57c2fc9597cb87eac9551af866885cd3
Author: Raymond Toy <toy.raymond at gmail.com>
Date:   Wed Nov 26 14:04:29 2014 -0800

    Fix some issues with log2 and log10 of big rationals.
    
     * src/code/irrat.lisp:
       * Add log10 function to handle the computation of the base 10 log
         of big rationals that might not fit in a double-float.
       * Fix some issues where CL:LOG wasn't handling logs of big
         rationals. (A regression).
     * tests/trac.lisp:
       * Update trac.8 test to include logs base 10.

diff --git a/src/code/irrat.lisp b/src/code/irrat.lisp
index 568fa46..325e5bc 100644
--- a/src/code/irrat.lisp
+++ b/src/code/irrat.lisp
@@ -645,6 +645,19 @@
 	   (log2-bignum x)
 	 (+ n frac))))))
 
+;; Handle the case where number could be so large that it doesn't fit
+;; in a double-float.
+(defun log10 (number &optional (float-type 1d0))
+  (let ((d (ignore-errors (float number 1d0))))
+    (cond (d
+	   ;; Number fits in a double, so it's easy
+	   (float (%log10 d) float-type))
+	  (t
+	   ;; Number doesn't fit in a double. Do it the hard way.
+	   ;; This should be done more accurately.
+	   (/ (log2 number float-type)
+	      (log2 (float 10 float-type)))))))
+  
 (defun log (number &optional (base nil base-p))
   "Return the logarithm of NUMBER in the base BASE, which defaults to e."
   (if base-p
@@ -667,12 +680,17 @@
 		  ((double-float
 		    (foreach integer ratio single-float double-float))
 		   (%log2 number))
-		  (((foreach integer ratio single-float)
+		  ((single-float double-float)
+		   (%log2 (float number 1d0)))
+		  ((single-float
 		    (foreach integer ratio single-float))
 		   (float (%log2 (float number 1d0)) 1f0))
-		  (((foreach integer ratio single-float)
+		  (((foreach integer ratio)
+		    (foreach integer ratio single-float))
+		   (log2 number 1f0))
+		  (((foreach integer ratio)
 		    double-float)
-		   (%log2 (float number 1d0)))
+		   (log2 number 1d0))
 		  #+double-double
 		  (((foreach integer ratio single-float double-float)
 		    double-double-float)
@@ -690,14 +708,19 @@
 		;; log base 2 and 10 for non-negative arguments.
 		(number-dispatch ((number real) (base real))
 		  ((double-float
-		    (foreach rational single-float double-float))
+		    (foreach integer ratio single-float double-float))
 		   (%log10 number))
-		  (((foreach integer ratio single-float)
+		  ((single-float double-float)
+		   (%log10 (float number 1d0)))
+		  ((single-float
 		    (foreach integer ratio single-float))
 		   (float (%log10 (float number 1d0)) 1f0))
-		  (((foreach integer ratio single-float)
+		  (((foreach integer ratio)
+		    (foreach integer ratio single-float))
+		   (log10 number 1f0))
+		  (((foreach integer ratio)
 		    double-float)
-		   (%log10 (float number 1d0)))
+		   (log10 number 1d0))
 		  #+double-double
 		  (((foreach integer ratio single-float double-float)
 		    ext:double-double-float)
diff --git a/tests/trac.lisp b/tests/trac.lisp
index 2bf420d..198a24d 100644
--- a/tests/trac.lisp
+++ b/tests/trac.lisp
@@ -22,7 +22,7 @@
   (:tag :trac)
   (assert-false
    (let (failures)
-     (dolist (base (list nil 2 2.0 2d0
+     (dolist (base (list nil 2 2.0 2d0 10 10.0 10d0
 			 (ash 1 99) (ash 1 3000)
 			 8/7 (/ (ash 1 3000) 7)))
        (dolist (number (list 100 100.0 100d0

-----------------------------------------------------------------------

Summary of changes:
 src/code/irrat.lisp | 37 ++++++++++++++++++++++++++++++-------
 tests/trac.lisp     |  2 +-
 2 files changed, 31 insertions(+), 8 deletions(-)


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