Implement new primitive INTEGER-LENGTH-IN-BITS. This computes the

length of a non-negative integer in the obvious way; it computes the
length of a negative integer by negating it and then returning the
value for the positive equivalent.

This primitive can be used to greatly speed up the conversion of
rational numbers to flonums.

diff --git a/v7/src/microcode/artutl.c b/v7/src/microcode/artutl.c
index 15fa583907e5a0e7ae98be79920938384df847ef..68aebb9b25049b80ab3cd0f0aa98bb26a7923099 100644 (file)
--- a/v7/src/microcode/artutl.c
+++ b/v7/src/microcode/artutl.c
@@ -1,8 +1,8 @@
 /* -*-C-*-
 
-$Id: artutl.c,v 1.12 1995/09/18 22:32:53 cph Exp $
+$Id: artutl.c,v 1.13 1997/04/22 22:42:16 cph Exp $
 
-Copyright (c) 1989-95 Massachusetts Institute of Technology
+Copyright (c) 1989-97 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -36,6 +36,7 @@ MIT in each case. */
 
 #include "scheme.h"
 #include <math.h>
+#include "limits.h"
 \f
 /* Conversions between Scheme types and C types. */
 
@@ -460,3 +461,25 @@ DEFUN (integer_remainder, (n, d), SCHEME_OBJECT n AND SCHEME_OBJECT d)
        : (bignum_to_integer (result)));
   }
 }
+\f
+SCHEME_OBJECT
+DEFUN (integer_length_in_bits, (n), SCHEME_OBJECT n)
+{
+  if (FIXNUM_P (n))
+    {
+      long n1 = (FIXNUM_TO_LONG (n));
+      unsigned long n2 = ((n1 < 0) ? (- n1) : n1);
+      unsigned long result = ((sizeof (unsigned long)) * CHAR_BIT);
+      unsigned long m = (1 << (result - 1));
+      while (result > 0)
+       {
+         if (n2 >= m)
+           break;
+         result -= 1;
+         m >>= 1;
+       }
+      return (LONG_TO_UNSIGNED_FIXNUM (result));
+    }
+  else
+    return (bignum_length_in_bits (n));
+}

diff --git a/v7/src/microcode/extern.h b/v7/src/microcode/extern.h
index 6b106e18063ea41b9a9af8b4e45e7a2e8e75497a..29e540923f28e6ca0246dd4fb63a9a577f310579 100644 (file)
--- a/v7/src/microcode/extern.h
+++ b/v7/src/microcode/extern.h
@@ -1,8 +1,8 @@
 /* -*-C-*-
 
-$Id: extern.h,v 9.53 1995/09/18 22:32:54 cph Exp $
+$Id: extern.h,v 9.54 1997/04/22 22:42:25 cph Exp $
 
-Copyright (c) 1987-95 Massachusetts Institute of Technology
+Copyright (c) 1987-97 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -205,6 +205,7 @@ extern Boolean EXFUN (integer_divide,
                       SCHEME_OBJECT *, SCHEME_OBJECT *));
 extern SCHEME_OBJECT EXFUN (integer_quotient, (SCHEME_OBJECT, SCHEME_OBJECT));
 extern SCHEME_OBJECT EXFUN (integer_remainder, (SCHEME_OBJECT, SCHEME_OBJECT));
+extern SCHEME_OBJECT EXFUN (integer_length_in_bits, (SCHEME_OBJECT));
 
 /* Character utilities */
 extern long EXFUN (char_downcase, (long));

diff --git a/v7/src/microcode/intprm.c b/v7/src/microcode/intprm.c
index 9a206b18bbb37f4712425c79a36dcb53362d0724..c7c15900c6eedb34da125576915efeb3e4407bf7 100644 (file)
--- a/v7/src/microcode/intprm.c
+++ b/v7/src/microcode/intprm.c
@@ -1,8 +1,8 @@
 /* -*-C-*-
 
-$Id: intprm.c,v 1.4 1992/08/29 13:20:43 jinx Exp $
+$Id: intprm.c,v 1.5 1997/04/22 22:42:41 cph Exp $
 
-Copyright (c) 1989-1992 Massachusetts Institute of Technology
+Copyright (c) 1989-97 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -108,6 +108,8 @@ DEFINE_PRIMITIVE ("INTEGER-ADD-1", Prim_integer_add_1, 1, 1, 0)
      INTEGER_UNARY_OPERATION (integer_add_1)
 DEFINE_PRIMITIVE ("INTEGER-SUBTRACT-1", Prim_integer_subtract_1, 1, 1, 0)
      INTEGER_UNARY_OPERATION (integer_subtract_1)
+DEFINE_PRIMITIVE ("INTEGER-LENGTH-IN-BITS", Prim_integer_length_in_bits, 1, 1, 0)
+     INTEGER_UNARY_OPERATION (integer_length_in_bits)
 \f
 DEFINE_PRIMITIVE ("INTEGER-DIVIDE", Prim_integer_divide, 2, 2, 0)
 {