1 files changed, 190 insertions, 0 deletions
diff --git a/libm/float/atanf.c b/libm/float/atanf.c
new file mode 100644
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+/*							atanf.c
+ *
+ *	Inverse circular tangent
+ *      (arctangent)
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * float x, y, atanf();
+ *
+ * y = atanf( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns radian angle between -pi/2 and +pi/2 whose tangent
+ * is x.
+ *
+ * Range reduction is from four intervals into the interval
+ * from zero to  tan( pi/8 ).  A polynomial approximates
+ * the function in this basic interval.
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ *                      Relative error:
+ * arithmetic   domain     # trials      peak         rms
+ *    IEEE      -10, 10     100000      1.9e-7      4.1e-8
+ *
+ */
+/*							atan2f()
+ *
+ *	Quadrant correct inverse circular tangent
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * float x, y, z, atan2f();
+ *
+ * z = atan2f( y, x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns radian angle whose tangent is y/x.
+ * Define compile time symbol ANSIC = 1 for ANSI standard,
+ * range -PI < z <= +PI, args (y,x); else ANSIC = 0 for range
+ * 0 to 2PI, args (x,y).
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ *                      Relative error:
+ * arithmetic   domain     # trials      peak         rms
+ *    IEEE      -10, 10     100000      1.9e-7      4.1e-8
+ * See atan.c.
+ *
+ */
+
+/*							atan.c */
+
+
+/*
+Cephes Math Library Release 2.2:  June, 1992
+Copyright 1984, 1987, 1989, 1992 by Stephen L. Moshier
+Direct inquiries to 30 Frost Street, Cambridge, MA 02140
+*/
+
+/* Single precision circular arcsine
+ * test interval: [-tan(pi/8), +tan(pi/8)]
+ * trials: 10000
+ * peak relative error: 7.7e-8
+ * rms relative error: 2.9e-8
+ */
+#include <math.h>
+extern float PIF, PIO2F, PIO4F;
+
+float atanf( float xx )
+{
+float x, y, z;
+int sign;
+
+x = xx;
+
+/* make argument positive and save the sign */
+if( xx < 0.0 )
+	{
+	sign = -1;
+	x = -xx;
+	}
+else
+	{
+	sign = 1;
+	x = xx;
+	}
+/* range reduction */
+if( x > 2.414213562373095 )  /* tan 3pi/8 */
+	{
+	y = PIO2F;
+	x = -( 1.0/x );
+	}
+
+else if( x > 0.4142135623730950 ) /* tan pi/8 */
+	{
+	y = PIO4F;
+	x = (x-1.0)/(x+1.0);
+	}
+else
+	y = 0.0;
+
+z = x * x;
+y +=
+((( 8.05374449538e-2 * z
+  - 1.38776856032E-1) * z
+  + 1.99777106478E-1) * z
+  - 3.33329491539E-1) * z * x
+  + x;
+
+if( sign < 0 )
+	y = -y;
+
+return( y );
+}
+
+
+
+
+float atan2f( float y, float x )
+{
+float z, w;
+int code;
+
+
+code = 0;
+
+if( x < 0.0 )
+	code = 2;
+if( y < 0.0 )
+	code |= 1;
+
+if( x == 0.0 )
+	{
+	if( code & 1 )
+		{
+#if ANSIC
+		return( -PIO2F );
+#else
+		return( 3.0*PIO2F );
+#endif
+		}
+	if( y == 0.0 )
+		return( 0.0 );
+	return( PIO2F );
+	}
+
+if( y == 0.0 )
+	{
+	if( code & 2 )
+		return( PIF );
+	return( 0.0 );
+	}
+
+
+switch( code )
+	{
+	default:
+#if ANSIC
+	case 0:
+	case 1: w = 0.0; break;
+	case 2: w = PIF; break;
+	case 3: w = -PIF; break;
+#else
+	case 0: w = 0.0; break;
+	case 1: w = 2.0 * PIF; break;
+	case 2:
+	case 3: w = PIF; break;
+#endif
+	}
+
+z = atanf( y/x );
+
+return( w + z );
+}
+