First cut at lgamma support

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1228 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

C/arith1.c

@@ -1077,6 +1077,57 @@ p_atanh(Term t E_ARGS)
   RFLOAT(out);
 }
 
+/*
+  lgamma(x) is the logarithm of the gamma function.
+*/
+static E_FUNC
+p_lgamma(Term t E_ARGS)
+{
+  Functor f = AritFunctorOfTerm(t);
+  union arith_ret v;
+  blob_type bt;
+  Float dbl, out;
+
+  switch (BlobOfFunctor(f)) {
+  case long_int_e:
+    dbl = IntegerOfTerm(t);
+    break;
+  case double_e:
+    dbl = FloatOfTerm(t);
+    break;
+#ifdef USE_GMP
+  case big_int_e:
+    dbl = mpz_get_d(Yap_BigIntOfTerm(t));
+    break;
+#endif
+  default:
+    /* we've got a full term, need to evaluate it first */
+    bt = Yap_Eval(t, &v);
+    /* second case, no need no evaluation */
+    switch (bt) {
+    case long_int_e:
+      dbl = v.Int;
+      break;
+    case double_e:
+      dbl = v.dbl;
+      break;
+#ifdef USE_GMP
+    case big_int_e:
+      dbl = mpz_get_d(v.big);
+      break;
+#endif
+    default:
+      /* Yap_Error */
+      RERROR();
+    }
+  }
+
+#if HAVE_LGAMMA
+  out = lgamma(dbl);
+#endif
+  RFLOAT(out);
+}
+
 /*
   floor(x) maximum integer greatest or equal to X
 
@@ -1961,6 +2012,7 @@ static InitUnEntry InitUnTab[] = {
   {"asin", p_asin},
   {"acos", p_acos},
   {"atan", p_atan},
+  {"lgamma", p_lgamma},
   {"asinh", p_asinh},
   {"acosh", p_acosh},
   {"atanh", p_atanh},