unified computation of pow_ui and pow_si in a function pow_usi, thereby

applying binary exponentiation in the case of negative exponent


git-svn-id: svn://scm.gforge.inria.fr/svn/mpc/trunk@788 211d60ee-9f03-0410-a15a-8952a2c7a4e4

1 files changed, 21 insertions, 17 deletions

diff --git a/src/pow_z.c b/src/pow_z.c
index 9b769fe..dcc0530 100644
--- a/src/pow_z.c
+++ b/src/pow_z.c
@@ -1,6 +1,6 @@
 /* mpc_pow_z -- Raise a complex number to an integer power.
 
-Copyright (C) 2009, 2010 Paul Zimmermann
+Copyright (C) 2009, 2010 Paul Zimmermann, Andreas Enge
 
 This file is part of the MPC Library.
 
@@ -24,21 +24,25 @@ MA 02111-1307, USA. */
 int
 mpc_pow_z (mpc_ptr z, mpc_srcptr x, mpz_srcptr y, mpc_rnd_t rnd)
 {
-  mpc_t yy;
-  int inex;
-  size_t n = mpz_sizeinbase (y, 2);
-
-  /* if y fits in an unsigned long or long, call the corresponding functions,
-     which are supposed to be more efficient */
-  if (mpz_fits_ulong_p (y))
-    return mpc_pow_ui (z, x, mpz_get_ui (y), rnd);
-  else if (mpz_fits_slong_p (y))
-    return mpc_pow_si (z, x, mpz_get_si (y), rnd);
-
-  mpc_init3 (yy, (n < MPFR_PREC_MIN) ? MPFR_PREC_MIN : n, MPFR_PREC_MIN);
-  mpc_set_z (yy, y, MPC_RNDNN);   /* exact */
-  inex = mpc_pow (z, x, yy, rnd);
-  mpc_clear (yy);
-  return inex;
+   mpc_t yy;
+   int inex;
+   size_t n = mpz_sizeinbase (y, 2);
+
+   /* if y fits in an unsigned long or long, call the corresponding functions,
+      which are supposed to be more efficient */
+   if (mpz_cmp_ui (y, 0ul) >= 0) {
+      if (mpz_fits_ulong_p (y))
+         return mpc_pow_usi (z, x, mpz_get_ui (y), 1, rnd);
+   }
+   else {
+      if (mpz_fits_slong_p (y))
+         return mpc_pow_usi (z, x, (unsigned long) (-mpz_get_si (y)), -1, rnd);
+   }
+
+   mpc_init3 (yy, (n < MPFR_PREC_MIN) ? MPFR_PREC_MIN : n, MPFR_PREC_MIN);
+   mpc_set_z (yy, y, MPC_RNDNN);   /* exact */
+   inex = mpc_pow (z, x, yy, rnd);
+   mpc_clear (yy);
+   return inex;
 }