[Guile-commits] GNU Guile branch, stable-2.0, updated. v2.0.0-177-gcf9d4a8

[Andy Wingo]

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http://git.savannah.gnu.org/cgit/guile.git/commit/?id=cf9d4a82146556ff45d40d6eec8579082287900e

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- Log -----------------------------------------------------------------
commit cf9d4a82146556ff45d40d6eec8579082287900e
Author: Ian Price <address@hidden>
Date:   Wed Apr 6 01:53:38 2011 +0100

    Added optional second arg to R6RS log function
    
    * module/rnrs/base.scm (log): now takes a base argument, using the
      change of base formula for logs.
    * test-suite/tests/r6rs-base.test ("log (2nd arg)"): Add test cases.

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

Summary of changes:
 module/rnrs/base.scm            |    9 +++++++++
 test-suite/tests/r6rs-base.test |   16 ++++++++++++++++
 2 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/module/rnrs/base.scm b/module/rnrs/base.scm
index b9dddab..b867929 100644
--- a/module/rnrs/base.scm
+++ b/module/rnrs/base.scm
@@ -74,6 +74,7 @@
 
          syntax-rules identifier-syntax)
   (import (rename (except (guile) error raise)
+                  (log log-internal)
                   (euclidean-quotient div)
                   (euclidean-remainder mod)
                   (euclidean/ div-and-mod)
@@ -85,6 +86,14 @@
                   (inexact->exact exact))
           (srfi srfi-11))
 
+ (define log
+   (case-lambda
+     ((n)
+      (log-internal n))
+     ((n base)
+      (/ (log n)
+         (log base)))))
+
  (define (boolean=? . bools)
    (define (boolean=?-internal lst last)
      (or (null? lst)
diff --git a/test-suite/tests/r6rs-base.test b/test-suite/tests/r6rs-base.test
index 1509b04..dfddf7c 100644
--- a/test-suite/tests/r6rs-base.test
+++ b/test-suite/tests/r6rs-base.test
@@ -21,6 +21,22 @@
   :use-module ((rnrs base) :version (6))
   :use-module (test-suite lib))
 
+
+;; numbers are considered =? if their difference is less than a set
+;; tolerance
+(define (=? alpha beta)
+  (< (abs (- alpha beta)) 1e-10))
+
+(with-test-prefix "log (2nd arg)"
+  (pass-if "log positive-base" (=? (log 8 2) 3))
+  (pass-if "log negative-base" (=? (real-part (log 256 -4))
+                                   0.6519359443))
+  (pass-if "log base-one" (= (log 10 1) +inf.0))
+  (pass-if "log base-zero"
+    (catch #t
+      (lambda () (log 10 0) #f)
+      (lambda args #t))))
+
 (with-test-prefix "boolean=?"
   (pass-if "boolean=? null" (boolean=?))
   (pass-if "boolean=? unary" (boolean=? #f))


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