fix R6RS log to accept 2 arguments

svn: r11197

collects/rnrs/base-6.ss

@@ -66,7 +66,7 @@
  numerator denominator
  floor ceiling truncate round
  rationalize
- exp log sin cos tan asin acos atan
+ exp (rename-out [r6rs:log log]) sin cos tan asin acos atan
  sqrt (rename-out [integer-sqrt/remainder exact-integer-sqrt])
  expt
  make-rectangular make-polar real-part imag-part magnitude 
@@ -296,6 +296,11 @@
                          args))
              (apply / args))]))
 
+(define r6rs:log
+  (case-lambda
+   [(n) (log n)]
+   [(n m) (/ (log n) (log m))]))
+
 (define (r6rs:angle n)
   ; because `angle' produces exact 0 for reals:
   (if (and (inexact-real? n) (positive? n))

collects/tests/r6rs/base.sls

@@ -842,6 +842,8 @@
     (test/approx (log 2.718281828459045) 1.0)
     (test (log +inf.0)                   +inf.0)
     (test (log 0.0)                      -inf.0)
+    (test/approx (log 100 10) 2.0)
+    (test/approx (log 1125899906842624 2) 50.0)
 
     (test/exn (log 0) &assertion)