add function LOG

http://clhs.lisp.se/Body/f_log.htm
jscl-project · May 5, 2023 · 4d7e110 · 4d7e110
1 parent 0c21063
commit 4d7e110
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diff --git a/src/numbers.lisp b/src/numbers.lisp
@@ -203,6 +203,15 @@
         (%ash-right x y)
         (%ash-left x  y))))
 
+;;; log
+(defun log (number &optional (base nil base-p))
+  "Return the logarithm of NUMBER in the base BASE, which defaults to e."
+  (if base-p
+      (/ (log number) (log base))
+      (if (numberp number)
+          (#j:Math:log number)
+          (error "`~S' is not a number." number))))
+
 ;;; lognot
 (defun lognot (x) (%lognot x))
 

diff --git a/tests/numbers.lisp b/tests/numbers.lisp
@@ -211,6 +211,14 @@
         (= #x3FFFC
            (ash #xFFFF 2))))
 
+;;; test LOG
+(test
+ (equal 0 (log 1)))
+(test
+ (equal 2 (log 100 10)))
+(test
+ (equal 3 (log 8.0 2)))
+
 ;;; test LOGNOT
 (test
  (equal '(-1 -2 0 999)