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authorAndy Wingo <wingo@pobox.com>2021-12-19 11:06:36 +0100
committerAndy Wingo <wingo@pobox.com>2022-01-13 09:37:16 +0100
commit89cd48fcac6c8b11a1a1cb155d3ddf6747719e7c (patch)
tree1a429a377d5f2fa90c9284d0b148a1d30160dcd7 /libguile
parent6298d731155ea35aecf68f21af81f1c4fd2f5e87 (diff)
downloadguile-89cd48fcac6c8b11a1a1cb155d3ddf6747719e7c.tar.gz
Implement scm_logbit_p with new integer library
* libguile/integers.c (scm_integer_logbit_ui, scm_integer_logbit_uz): * libguile/integers.h: Declare the new internal functions. * libguile/numbers.c (scm_logbit_p): Use new internal functions.
Diffstat (limited to 'libguile')
-rw-r--r--libguile/integers.c20
-rw-r--r--libguile/integers.h3
-rw-r--r--libguile/numbers.c18
3 files changed, 25 insertions, 16 deletions
diff --git a/libguile/integers.c b/libguile/integers.c
index ff5499af9..fc71c7acc 100644
--- a/libguile/integers.c
+++ b/libguile/integers.c
@@ -2008,3 +2008,23 @@ scm_integer_logtest_zz (SCM x, SCM y)
{
return scm_is_eq (scm_integer_logand_zz (x, y), SCM_INUM0);
}
+
+int
+scm_integer_logbit_ui (unsigned long index, scm_t_inum n)
+{
+ if (index < SCM_LONG_BIT)
+ /* Assume two's complement representation. */
+ return (n >> index) & 1;
+ else
+ return n < 0;
+}
+
+int
+scm_integer_logbit_uz (unsigned long index, SCM n)
+{
+ mpz_t zn;
+ alias_bignum_to_mpz (scm_bignum (n), zn);
+ int val = mpz_tstbit (zn, index);
+ scm_remember_upto_here_1 (n);
+ return val;
+}
diff --git a/libguile/integers.h b/libguile/integers.h
index 56334f0a8..feba5963f 100644
--- a/libguile/integers.h
+++ b/libguile/integers.h
@@ -148,6 +148,9 @@ SCM_INTERNAL int scm_integer_logtest_ii (scm_t_inum x, scm_t_inum y);
SCM_INTERNAL int scm_integer_logtest_zi (SCM x, scm_t_inum y);
SCM_INTERNAL int scm_integer_logtest_zz (SCM x, SCM y);
+SCM_INTERNAL int scm_integer_logbit_ui (unsigned long bit, scm_t_inum n);
+SCM_INTERNAL int scm_integer_logbit_uz (unsigned long bit, SCM n);
+
#endif /* SCM_INTEGERS_H */
diff --git a/libguile/numbers.c b/libguile/numbers.c
index 26d1c061f..548618e74 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -3155,23 +3155,9 @@ SCM_DEFINE (scm_logbit_p, "logbit?", 2, 0, 0,
iindex = scm_to_ulong (index);
if (SCM_I_INUMP (j))
- {
- if (iindex < SCM_LONG_BIT - 1)
- /* Arrange for the number to be converted to unsigned before
- checking the bit, to ensure that we're testing the bit in a
- two's complement representation (regardless of the native
- representation. */
- return scm_from_bool ((1UL << iindex) & SCM_I_INUM (j));
- else
- /* Portably check the sign. */
- return scm_from_bool (SCM_I_INUM (j) < 0);
- }
+ return scm_from_bool (scm_integer_logbit_ui (iindex, SCM_I_INUM (j)));
else if (SCM_BIGP (j))
- {
- int val = mpz_tstbit (SCM_I_BIG_MPZ (j), iindex);
- scm_remember_upto_here_1 (j);
- return scm_from_bool (val);
- }
+ return scm_from_bool (scm_integer_logbit_uz (iindex, j));
else
SCM_WRONG_TYPE_ARG (SCM_ARG2, j);
}