1 files changed, 64 insertions, 0 deletions
diff --git a/src/math/atanhl.c b/src/math/atanhl.c
new file mode 100644
index 00000000..af0f856d
--- /dev/null
+++ b/src/math/atanhl.c
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+/* origin: OpenBSD /usr/src/lib/libm/src/ld80/e_atanh.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/* atanhl(x)
+ * Method :
+ *    1.Reduced x to positive by atanh(-x) = -atanh(x)
+ *    2.For x>=0.5
+ *                   1              2x                          x
+ *      atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
+ *                   2             1 - x                      1 - x
+ *
+ *      For x<0.5
+ *      atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
+ *
+ * Special cases:
+ *      atanhl(x) is NaN if |x| > 1 with signal;
+ *      atanhl(NaN) is that NaN with no signal;
+ *      atanhl(+-1) is +-INF with signal.
+ */
+
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double atanhl(long double x)
+{
+	return atanh(x);
+}
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+static const long double zero = 0.0, one = 1.0, huge = 1e4900L;
+
+long double atanhl(long double x)
+{
+	long double t;
+	int32_t ix;
+	uint32_t se,i0,i1;
+
+	GET_LDOUBLE_WORDS(se, i0, i1, x);
+	ix = se & 0x7fff;
+	if ((ix+((((i0&0x7fffffff)|i1)|(-((i0&0x7fffffff)|i1)))>>31)) > 0x3fff)
+		/* |x| > 1 */
+		return (x-x)/(x-x);
+	if (ix == 0x3fff)
+		return x/zero;
+	if (ix < 0x3fe3 && huge+x > zero)  /* x < 2**-28 */
+		return x;
+	SET_LDOUBLE_EXP(x, ix);
+	if (ix < 0x3ffe) {  /* x < 0.5 */
+		t = x + x;
+		t = 0.5*log1pl(t + t*x/(one-x));
+	} else
+		t = 0.5*log1pl((x + x)/(one - x));
+	if (se <= 0x7fff)
+		return t;
+	return -t;
+}
+#endif