mini-gmp: Implemented mpz_cmpabs_d.

3 files changed, 54 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 2db15b0b4..c57ee4394 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2013-01-22  Niels Möller  <nisse@lysator.liu.se>
+
+	* mini-gmp/mini-gmp.c (mpz_cmpabs_d): New function.
+	* mini-gmp/mini-gmp.h: Declare it.
+
 2013-01-21  Niels Möller  <nisse@lysator.liu.se>
 
 	* mini-gmp/tests/t-str.c (testmain): Test mpz_out_str, using
diff --git a/mini-gmp/mini-gmp.c b/mini-gmp/mini-gmp.c
index 5d16d76f1..bf1b2dc2f 100644
--- a/mini-gmp/mini-gmp.c
+++ b/mini-gmp/mini-gmp.c
@@ -1545,6 +1545,54 @@ mpz_get_d (const mpz_t u)
 }
 
 int
+mpz_cmpabs_d (const mpz_t x, double d)
+{
+  mp_size_t xn;
+  double B, Bi;
+  mp_size_t i;
+
+  xn = GMP_ABS (x->_mp_size);
+  d = GMP_ABS (d);
+
+  if (xn == 0)
+    return - (d > 0.0);
+  if (d < 1.0)
+    return 1;
+
+  B = 2.0 * (double) GMP_LIMB_HIGHBIT;
+  Bi = 1.0 / B;
+
+  /* Scale d so it can be compared with the top limb. */
+  for (i = 1; i < xn; i++)
+    {
+      d *= Bi;
+      if (d < 1.0)
+	return 1;
+    }
+  if (d >= B)
+    return -1;
+
+  /* Subtract x from d, one limb at a time. */
+  for (i = xn; i-- > 0;)
+    {
+      mp_limb_t f, xl;
+
+      f = (mp_limb_t) d;
+      xl = x->_mp_d[i];
+      if (xl > f)
+	return 1;
+      else if (xl < f)
+	return -1;
+      d = B * (d - f);
+    }
+
+  if (d > 0)
+    return -1;
+  else
+    return 0;  
+}
+
+int
 mpz_cmp_d (const mpz_t x, double d)
 {
   mp_size_t xn = x->_mp_size;
diff --git a/mini-gmp/mini-gmp.h b/mini-gmp/mini-gmp.h
index edcaa7555..8c94ca2ed 100644
--- a/mini-gmp/mini-gmp.h
+++ b/mini-gmp/mini-gmp.h
@@ -108,6 +108,7 @@ int mpz_cmp (const mpz_t, const mpz_t);
 int mpz_cmpabs_ui (const mpz_t, unsigned long);
 int mpz_cmpabs (const mpz_t, const mpz_t);
 int mpz_cmp_d (const mpz_t, double);
+int mpz_cmpabs_d (const mpz_t, double);
 
 void mpz_abs (mpz_t, const mpz_t);
 void mpz_neg (mpz_t, const mpz_t);