X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Fbignum.lisp;h=03f23377ab672d40899065e3c00ab4d75fc8a280;hb=62c09fabe8aa8f1bd75bf4db4c20e195a1b6bc1d;hp=f7f7e5d0cb8897328c307fabcb8d2be1ce27eca5;hpb=b953c186cfe68e48801cb54715da0120c9580888;p=sbcl.git

diff --git a/src/code/bignum.lisp b/src/code/bignum.lisp
index f7f7e5d..03f2337 100644
--- a/src/code/bignum.lisp
+++ b/src/code/bignum.lisp
@@ -22,7 +22,7 @@
 ;;;       bignum-logical-and bignum-logical-ior bignum-logical-xor
 ;;;       bignum-logical-not bignum-load-byte bignum-deposit-byte
 ;;;       bignum-truncate bignum-plus-p bignum-compare make-small-bignum
-;;;       bignum-logcount
+;;;       bignum-logbitp bignum-logcount
 ;;;   These symbols define the interface to the compiler:
 ;;;       bignum-type bignum-element-type bignum-index %allocate-bignum
 ;;;       %bignum-length %bignum-set-length %bignum-ref %bignum-set
@@ -1009,7 +1009,7 @@
      (t
       (round-up))))))
 
-;;;; integer length and logcount
+;;;; integer length and logbitp/logcount
 
 (defun bignum-integer-length (bignum)
   (declare (type bignum-type bignum))
@@ -1021,6 +1021,17 @@
     (+ (integer-length (%fixnum-digit-with-correct-sign digit))
        (* len-1 digit-size))))
 
+(defun bignum-logbitp (index bignum)
+  (declare (type bignum-type bignum))
+  (let ((len (%bignum-length bignum)))
+    (declare (type bignum-index len))
+    (multiple-value-bind (word-index bit-index)
+	(floor index digit-size)
+      (if (>= word-index len)
+	  (not (bignum-plus-p bignum))
+	  (not (zerop (logand (%bignum-ref bignum word-index)
+			      (ash 1 bit-index))))))))
+
 (defun bignum-logcount (bignum)
   (declare (type bignum-type bignum))
   (let* ((length (%bignum-length bignum))