1 files changed, 106 insertions, 0 deletions
diff --git a/mpfr/pow_ui.c b/mpfr/pow_ui.c
new file mode 100644
index 000000000..42a3ee3ee
--- /dev/null
+++ b/mpfr/pow_ui.c
@@ -0,0 +1,106 @@
+/* mpfr_pow_ui-- compute the power of a floating-point
+                                  by a machine integer
+
+Copyright (C) 1999, 2001 Free Software Foundation, Inc.
+
+This file is part of the MPFR Library.
+
+The MPFR Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or (at your
+option) any later version.
+
+The MPFR Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the MPFR Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA. */
+
+#include <stdio.h>
+#include "gmp.h"
+#include "mpfr.h"
+#include "mpfr-impl.h"
+
+/* sets x to y^n, and return 0 if exact, non-zero otherwise */
+int
+mpfr_pow_ui (mpfr_ptr x, mpfr_srcptr y, unsigned long int n, mp_rnd_t rnd)
+{
+  long int i, err;
+  unsigned long m;
+  mpfr_t res;
+  mp_prec_t prec;
+  int inexact;
+  mp_rnd_t rnd1;
+
+  if (MPFR_IS_NAN(y))
+    {
+      MPFR_SET_NAN(x);
+      MPFR_RET_NAN;
+    }
+
+  MPFR_CLEAR_NAN(x);
+
+  if (n == 0) /* x^0 = 1 for any x */
+    {
+      mpfr_set_ui (x, 1, rnd);
+      return 0;
+    }
+
+  if (MPFR_IS_INF(y)) 
+    {
+      /* Inf^n = Inf, (-Inf)^n = Inf for n even, -Inf for n odd */
+      if ((MPFR_SIGN(y) < 0) && (n % 2 == 1))
+	{
+	  if (MPFR_SIGN(x) > 0)
+	    MPFR_CHANGE_SIGN(x);
+	}
+      else if (MPFR_SIGN(x) < 0)
+	MPFR_CHANGE_SIGN(x);
+      MPFR_SET_INF(x);
+      return 0;
+    }
+  
+  MPFR_CLEAR_INF(x);
+
+  mpfr_init (res);
+
+  prec = MPFR_PREC(x);
+
+  rnd1 = (MPFR_SIGN(y) > 0) ? GMP_RNDU : GMP_RNDD; /* away */
+
+  do
+    {
+      prec += 3;
+      for (m=n, i=0; m; i++, m>>=1, prec++);
+      mpfr_set_prec (res, prec);
+      inexact = mpfr_set (res, y, rnd1);
+      err = 1;
+      /* now 2^(i-1) <= n < 2^i */
+      for (i-=2; i>=0; i--)
+	{
+	  if (mpfr_mul (res, res, res, GMP_RNDU))
+	    inexact = 1;
+	  err++;
+	  if (n & (1 << i))
+	    if (mpfr_mul (res, res, y, rnd1))
+	      inexact = 1;
+	}
+      err = prec - err;
+      if (err < 0)
+	err = 0;
+    }
+  while (inexact && (mpfr_can_round (res, err,
+	  (MPFR_SIGN(res) > 0) ? GMP_RNDU : GMP_RNDD, rnd, MPFR_PREC(x)) == 0));
+
+  if (mpfr_set (x, res, rnd))
+    inexact = 1;
+
+  mpfr_clear (res);
+
+  return inexact;
+}
+