Initial revision

lang/cem/libcc/math/cosh.c

@@ -0,0 +1,38 @@
+/*
+ * (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
+ * See the copyright notice in the ACK home directory, in the file "Copyright".
+ *
+ * Author: Ceriel J.H. Jacobs
+ */
+
+/* $Header$ */
+
+#include <math.h>
+#include <errno.h>
+
+extern int errno;
+
+double
+cosh(x)
+	double x;
+{
+	extern double exp();
+
+	if (x < 0) {
+		x = -x;
+	}
+	if (x > M_LN_MAX_D) {
+		/* exp(x) would overflow */
+		if (x >= M_LN_MAX_D + M_LN2) {
+			/* not representable */
+			x = HUGE;
+			errno = ERANGE;
+		}
+		else	x = exp (x - M_LN2);
+	}
+	else {
+		double expx = exp(x);
+		x = 0.5 * (expx + 1.0/expx);
+	}
+	return x;
+}