From 524df8da1b8fba4e6e7eeeb3506490def9bf1612 Mon Sep 17 00:00:00 2001
From: David 'Epper' Marshall <epper.marshall@gmail.com>
Date: Mon, 20 Jun 2022 17:17:49 -0400
Subject: [PATCH] math: add zpl stuff (#14543)

---
 vlib/math/const.v     | 39 ++++++++++++++++++++++++---------------
 vlib/math/math.v      |  9 +++++++++
 vlib/math/math_test.v | 10 ++++++++++
 3 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/vlib/math/const.v b/vlib/math/const.v
index df1460dab..61226f3c0 100644
--- a/vlib/math/const.v
+++ b/vlib/math/const.v
@@ -4,21 +4,30 @@
 module math
 
 pub const (
-	e        = 2.71828182845904523536028747135266249775724709369995957496696763
-	pi       = 3.14159265358979323846264338327950288419716939937510582097494459
-	pi_2     = pi / 2.0
-	pi_4     = pi / 4.0
-	phi      = 1.61803398874989484820458683436563811772030917980576286213544862
-	tau      = 6.28318530717958647692528676655900576839433879875021164194988918
-	sqrt2    = 1.41421356237309504880168872420969807856967187537694807317667974
-	sqrt_e   = 1.64872127070012814684865078781416357165377610071014801157507931
-	sqrt_pi  = 1.77245385090551602729816748334114518279754945612238712821380779
-	sqrt_tau = 2.50662827463100050241576528481104525300698674060993831662992357
-	sqrt_phi = 1.27201964951406896425242246173749149171560804184009624861664038
-	ln2      = 0.693147180559945309417232121458176568075500134360255254120680009
-	log2_e   = 1.0 / ln2
-	ln10     = 2.30258509299404568401799145468436420760110148862877297603332790
-	log10_e  = 1.0 / ln10
+	epsilon      = 2.2204460492503130808472633361816E-16
+	e            = 2.71828182845904523536028747135266249775724709369995957496696763
+	pi           = 3.14159265358979323846264338327950288419716939937510582097494459
+	pi_2         = pi / 2.0
+	pi_4         = pi / 4.0
+	phi          = 1.61803398874989484820458683436563811772030917980576286213544862
+	tau          = 6.28318530717958647692528676655900576839433879875021164194988918
+	one_over_tau = 1.0 / tau
+	one_over_pi  = 1.0 / pi
+	tau_over2    = tau / 2.0
+	tau_over4    = tau / 4.0
+	tau_over8    = tau / 8.0
+	sqrt2        = 1.41421356237309504880168872420969807856967187537694807317667974
+	sqrt_3       = 1.73205080756887729352744634150587236694280525381038062805580697
+	sqrt_5       = 2.23606797749978969640917366873127623544061835961152572427089724
+	sqrt_e       = 1.64872127070012814684865078781416357165377610071014801157507931
+	sqrt_pi      = 1.77245385090551602729816748334114518279754945612238712821380779
+	sqrt_tau     = 2.50662827463100050241576528481104525300698674060993831662992357
+	sqrt_phi     = 1.27201964951406896425242246173749149171560804184009624861664038
+	ln2          = 0.693147180559945309417232121458176568075500134360255254120680009
+	log2_e       = 1.0 / ln2
+	ln10         = 2.30258509299404568401799145468436420760110148862877297603332790
+	log10_e      = 1.0 / ln10
+	two_thirds   = 0.66666666666666666666666666666666666666666666666666666666666667
 )
 
 // Floating-point limit values
diff --git a/vlib/math/math.v b/vlib/math/math.v
index 71562b04d..5c404d0a4 100644
--- a/vlib/math/math.v
+++ b/vlib/math/math.v
@@ -42,6 +42,15 @@ pub fn degrees(radians f64) f64 {
 	return radians * (180.0 / pi)
 }
 
+// angle_diff calculates the difference between angles in radians
+[inline]
+pub fn angle_diff(radian_a f64, radian_b f64) f64 {
+	mut delta := fmod(radian_b - radian_a, tau)
+	delta = fmod(delta + 1.5 * tau, tau)
+	delta -= .5 * tau
+	return delta
+}
+
 [params]
 pub struct DigitParams {
 	base    int = 10
diff --git a/vlib/math/math_test.v b/vlib/math/math_test.v
index aeaabf0a1..fc2d16cd1 100644
--- a/vlib/math/math_test.v
+++ b/vlib/math/math_test.v
@@ -222,6 +222,16 @@ fn test_nan() {
 	assert nan_f32 != nan_f32
 }
 
+fn test_angle_diff() {
+	for pair in [
+		[pi, pi_2, -pi_2],
+		[pi_2 * 3.0, pi_2, -pi],
+		[pi / 6.0, two_thirds * pi, pi_2],
+	] {
+		assert angle_diff(pair[0], pair[1]) == pair[2]
+	}
+}
+
 fn test_acos() {
 	for i := 0; i < math.vf_.len; i++ {
 		a := math.vf_[i] / 10
-- 
2.30.2