1 files changed, 76 insertions, 0 deletions
diff --git a/mpc/src/acosh.c b/mpc/src/acosh.c
new file mode 100644
index 0000000000..782f5550c2
--- /dev/null
+++ b/mpc/src/acosh.c
@@ -0,0 +1,76 @@
+/* mpc_acosh -- inverse hyperbolic cosine of a complex number.
+
+Copyright (C) 2009, 2011, 2012 INRIA
+
+This file is part of GNU MPC.
+
+GNU MPC 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 3 of the License, or (at your
+option) any later version.
+
+GNU MPC 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 this program. If not, see http://www.gnu.org/licenses/ .
+*/
+
+#include "mpc-impl.h"
+
+int
+mpc_acosh (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
+{
+  /* acosh(z) =
+      NaN + i*NaN, if z=0+i*NaN
+     -i*acos(z), if sign(Im(z)) = -
+      i*acos(z), if sign(Im(z)) = +
+      http://functions.wolfram.com/ElementaryFunctions/ArcCosh/27/02/03/01/01/
+  */
+  mpc_t a;
+  mpfr_t tmp;
+  int inex;
+
+  if (mpfr_zero_p (mpc_realref (op)) && mpfr_nan_p (mpc_imagref (op)))
+    {
+      mpfr_set_nan (mpc_realref (rop));
+      mpfr_set_nan (mpc_imagref (rop));
+      return 0;
+    }
+
+  /* Note reversal of precisions due to later multiplication by i or -i */
+  mpc_init3 (a, MPC_PREC_IM(rop), MPC_PREC_RE(rop));
+
+  if (mpfr_signbit (mpc_imagref (op)))
+    {
+      inex = mpc_acos (a, op,
+                       MPC_RND (INV_RND (MPC_RND_IM (rnd)), MPC_RND_RE (rnd)));
+
+      /* change a to -i*a, i.e., -y+i*x to x+i*y */
+      tmp[0] = mpc_realref (a)[0];
+      mpc_realref (a)[0] = mpc_imagref (a)[0];
+      mpc_imagref (a)[0] = tmp[0];
+      MPFR_CHANGE_SIGN (mpc_imagref (a));
+      inex = MPC_INEX (MPC_INEX_IM (inex), -MPC_INEX_RE (inex));
+    }
+  else
+    {
+      inex = mpc_acos (a, op,
+                       MPC_RND (MPC_RND_IM (rnd), INV_RND(MPC_RND_RE (rnd))));
+
+      /* change a to i*a, i.e., y-i*x to x+i*y */
+      tmp[0] = mpc_realref (a)[0];
+      mpc_realref (a)[0] = mpc_imagref (a)[0];
+      mpc_imagref (a)[0] = tmp[0];
+      MPFR_CHANGE_SIGN (mpc_realref (a));
+      inex = MPC_INEX (-MPC_INEX_IM (inex), MPC_INEX_RE (inex));
+    }
+
+  mpc_set (rop, a, rnd);
+
+  mpc_clear (a);
+
+  return inex;
+}