From f5c4671bfbad96bf346bd7e9a21fc4317b4959df Mon Sep 17 00:00:00 2001
From: Indrajith K L
Date: Sat, 3 Dec 2022 17:00:20 +0530
Subject: Adds most of the tools

---
 v_windows/v/vlib/math/invtrig.v | 219 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 219 insertions(+)
 create mode 100644 v_windows/v/vlib/math/invtrig.v

(limited to 'v_windows/v/vlib/math/invtrig.v')

diff --git a/v_windows/v/vlib/math/invtrig.v b/v_windows/v/vlib/math/invtrig.v
new file mode 100644
index 0000000..c40d87f
--- /dev/null
+++ b/v_windows/v/vlib/math/invtrig.v
@@ -0,0 +1,219 @@
+module math
+
+// The original C code, the long comment, and the constants below were
+// from http://netlib.sandia.gov/cephes/cmath/atan.c, available from
+// http://www.netlib.org/cephes/ctgz.
+// The go code is a version of the original C.
+//
+// atan.c
+// Inverse circular tangent (arctangent)
+//
+// SYNOPSIS:
+// double x, y, atan()
+// y = atan( x )
+//
+// DESCRIPTION:
+// Returns radian angle between -pi/2.0 and +pi/2.0 whose tangent is x.
+//
+// Range reduction is from three intervals into the interval from zero to 0.66.
+// The approximant uses a rational function of degree 4/5 of the form
+// x + x**3 P(x)/Q(x).
+//
+// ACCURACY:
+// Relative error:
+// arithmetic   domain    # trials  peak     rms
+// DEC       -10, 10   50000     2.4e-17  8.3e-18
+// IEEE      -10, 10   10^6      1.8e-16  5.0e-17
+//
+// Cephes Math Library Release 2.8:  June, 2000
+// Copyright 1984, 1987, 1989, 1992, 2000 by Stephen L. Moshier
+//
+// The readme file at http://netlib.sandia.gov/cephes/ says:
+// Some software in this archive may be from the book _Methods and
+// Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster
+// International, 1989) or from the Cephes Mathematical Library, a
+// commercial product. In either event, it is copyrighted by the author.
+// What you see here may be used freely but it comes with no support or
+// guarantee.
+//
+// The two known misprints in the book are repaired here in the
+// source listings for the gamma function and the incomplete beta
+// integral.
+//
+// Stephen L. Moshier
+// moshier@na-net.ornl.gov
+// pi/2.0 = PIO2 + morebits
+// tan3pio8 = tan(3*pi/8)
+
+const (
+	morebits = 6.123233995736765886130e-17
+	tan3pio8 = 2.41421356237309504880
+)
+
+// xatan evaluates a series valid in the range [0, 0.66].
+[inline]
+fn xatan(x f64) f64 {
+	xatan_p0 := -8.750608600031904122785e-01
+	xatan_p1 := -1.615753718733365076637e+01
+	xatan_p2 := -7.500855792314704667340e+01
+	xatan_p3 := -1.228866684490136173410e+02
+	xatan_p4 := -6.485021904942025371773e+01
+	xatan_q0 := 2.485846490142306297962e+01
+	xatan_q1 := 1.650270098316988542046e+02
+	xatan_q2 := 4.328810604912902668951e+02
+	xatan_q3 := 4.853903996359136964868e+02
+	xatan_q4 := 1.945506571482613964425e+02
+	mut z := x * x
+	z = z * ((((xatan_p0 * z + xatan_p1) * z + xatan_p2) * z + xatan_p3) * z + xatan_p4) / (((((z +
+		xatan_q0) * z + xatan_q1) * z + xatan_q2) * z + xatan_q3) * z + xatan_q4)
+	z = x * z + x
+	return z
+}
+
+// satan reduces its argument (known to be positive)
+// to the range [0, 0.66] and calls xatan.
+[inline]
+fn satan(x f64) f64 {
+	if x <= 0.66 {
+		return xatan(x)
+	}
+	if x > math.tan3pio8 {
+		return pi / 2.0 - xatan(1.0 / x) + f64(math.morebits)
+	}
+	return pi / 4 + xatan((x - 1.0) / (x + 1.0)) + 0.5 * f64(math.morebits)
+}
+
+// atan returns the arctangent, in radians, of x.
+//
+// special cases are:
+// atan(±0) = ±0
+// atan(±inf) = ±pi/2.0
+pub fn atan(x f64) f64 {
+	if x == 0 {
+		return x
+	}
+	if x > 0 {
+		return satan(x)
+	}
+	return -satan(-x)
+}
+
+// atan2 returns the arc tangent of y/x, using
+// the signs of the two to determine the quadrant
+// of the return value.
+//
+// special cases are (in order):
+// atan2(y, nan) = nan
+// atan2(nan, x) = nan
+// atan2(+0, x>=0) = +0
+// atan2(-0, x>=0) = -0
+// atan2(+0, x<=-0) = +pi
+// atan2(-0, x<=-0) = -pi
+// atan2(y>0, 0) = +pi/2.0
+// atan2(y<0, 0) = -pi/2.0
+// atan2(+inf, +inf) = +pi/4
+// atan2(-inf, +inf) = -pi/4
+// atan2(+inf, -inf) = 3pi/4
+// atan2(-inf, -inf) = -3pi/4
+// atan2(y, +inf) = 0
+// atan2(y>0, -inf) = +pi
+// atan2(y<0, -inf) = -pi
+// atan2(+inf, x) = +pi/2.0
+// atan2(-inf, x) = -pi/2.0
+pub fn atan2(y f64, x f64) f64 {
+	// special cases
+	if is_nan(y) || is_nan(x) {
+		return nan()
+	}
+	if y == 0.0 {
+		if x >= 0 && !signbit(x) {
+			return copysign(0, y)
+		}
+		return copysign(pi, y)
+	}
+	if x == 0.0 {
+		return copysign(pi / 2.0, y)
+	}
+	if is_inf(x, 0) {
+		if is_inf(x, 1) {
+			if is_inf(y, 0) {
+				return copysign(pi / 4, y)
+			}
+			return copysign(0, y)
+		}
+		if is_inf(y, 0) {
+			return copysign(3.0 * pi / 4.0, y)
+		}
+		return copysign(pi, y)
+	}
+	if is_inf(y, 0) {
+		return copysign(pi / 2.0, y)
+	}
+	// Call atan and determine the quadrant.
+	q := atan(y / x)
+	if x < 0 {
+		if q <= 0 {
+			return q + pi
+		}
+		return q - pi
+	}
+	return q
+}
+
+/*
+Floating-point arcsine and arccosine.
+
+	They are implemented by computing the arctangent
+	after appropriate range reduction.
+*/
+
+// asin returns the arcsine, in radians, of x.
+//
+// special cases are:
+// asin(±0) = ±0
+// asin(x) = nan if x < -1 or x > 1
+pub fn asin(x_ f64) f64 {
+	mut x := x_
+	if x == 0.0 {
+		return x // special case
+	}
+	mut sign := false
+	if x < 0.0 {
+		x = -x
+		sign = true
+	}
+	if x > 1.0 {
+		return nan() // special case
+	}
+	mut temp := sqrt(1.0 - x * x)
+	if x > 0.7 {
+		temp = pi / 2.0 - satan(temp / x)
+	} else {
+		temp = satan(x / temp)
+	}
+	if sign {
+		temp = -temp
+	}
+	return temp
+}
+
+// acos returns the arccosine, in radians, of x.
+//
+// special case is:
+// acos(x) = nan if x < -1 or x > 1
+[inline]
+pub fn acos(x f64) f64 {
+	if (x < -1.0) || (x > 1.0) {
+		return nan()
+	}
+	if x == 0.0 {
+		return nan()
+	}
+	if x > 0.5 {
+		return f64(2.0) * asin(sqrt(0.5 - 0.5 * x))
+	}
+	mut z := pi / f64(4.0) - asin(x)
+	z = z + math.morebits
+	z = z + pi / f64(4.0)
+	return z
+}
-- 
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