X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/blobdiff_plain/95f51977ddc18faa2e212f30c00a39540b39f325..ca67e7b465996afb3821d6a075c4dc6a7f0f5d52:/usr/src/usr.lib/libF77/r_tan.c

diff --git a/usr/src/usr.lib/libF77/r_tan.c b/usr/src/usr.lib/libF77/r_tan.c
index c996cb6845..7a99d7c9c3 100644
--- a/usr/src/usr.lib/libF77/r_tan.c
+++ b/usr/src/usr.lib/libF77/r_tan.c
@@ -3,12 +3,87 @@
  * All rights reserved.  The Berkeley software License Agreement
  * specifies the terms and conditions for redistribution.
  *
- *	@(#)r_tan.c	5.2	7/8/85
+ *	@(#)r_tan.c	5.3	11/3/86
  */
 
+#ifndef tahoe
 float r_tan(x)
 float *x;
 {
 double tan();
 return( tan(*x) );
 }
+
+#else tahoe
+
+/*
+	SINGLE PRECISION floating point tangent
+
+	sin/cos is used after argument reduction to [0,pi/4] range.
+	since x is in this range, tan(x) is in [0,1] range and
+	no overflow can occur here.
+*/
+
+#include <errno.h>
+
+int	errno;
+static double invpi = 1.27323954473516268;  /* 4/pi */
+
+float
+r_tan(parg)
+float *parg;
+{
+	double arg;
+	fortran float sin(), cos();
+	double modf();
+	float flmax_();
+	double temp, e, x, xsq;
+	int sign;
+	int flag, i;
+
+	arg = *parg;
+	flag = 0;
+	sign = 1.;
+	if(arg < 0.){		/* tan(-arg) = -tan(arg) */
+		arg = -arg;
+		sign = -1.;
+	}
+	arg = arg*invpi;   /*overflow?*/
+	x = modf(arg,&e);
+	i = e;
+	switch(i%4) {
+	case 1:			/* 2nd octant: tan(x) = 1/tan(1-x) */
+		x = 1. - x;
+		flag = 1;
+		break;
+
+	case 2:			/* 3rd octant: tan(x) = -1/tan(x) */
+		sign = - sign;
+		flag = 1;
+		break;
+
+	case 3:			/* 4th octant: tan(x) = -tan(1-x) */
+		x = 1. - x;
+		sign = - sign;
+		break;
+
+	case 0:			/* 1st octant */
+		break;
+	}
+	x = x/invpi;
+
+	temp = sin(x)/cos(x);
+
+	if(flag == 1) {
+		if(temp == 0.) {	/* check for singular "point" */
+			errno = ERANGE;
+			if (sign>0)
+				return(flmax_());
+			return(-flmax_());
+		}
+		temp = 1./temp;
+	}
+	return(sign*temp);
+}
+
+#endif tahoe