add angle func

vlib/math/complex.v

@@ -26,6 +26,11 @@ pub fn (c Complex) str() string {
 	return out
 }
 
+// Complex Angle
+pub fn (c Complex) angle() f64 { 
+	return atan2(c.im, c.re)
+}
+
 // Complex Addition c1 + c2
 pub fn (c1 Complex) + (c2 Complex) Complex {
 	return Complex{c1.re+c2.re,c1.im+c2.im}
@@ -90,4 +95,4 @@ pub fn (c1 Complex) conjugate() Complex{
 // Complex Equals
 pub fn (c1 Complex) equals(c2 Complex) bool {
 	return (c1.re == c2.re) && (c1.im == c2.im)
-}
+}

vlib/math/complex_test.v

@@ -101,4 +101,19 @@ fn test_complex_equals() {
 	c1 = math.complex(-3,19)
 	c2 = math.complex(-3,19)
 	assert c1.equals(c2)
-}
+}
+
+fn test_complex_angle(){
+	mut c := math.complex(1, 0)
+	assert c.angle() * 180 / math.Pi == 0
+	c = math.complex(1, 1)
+	assert c.angle() * 180 / math.Pi == 45
+	c = math.complex(0, 1)
+	assert c.angle() * 180 / math.Pi == 90
+	c = math.complex(-1, 1)
+	assert c.angle() * 180 / math.Pi == 135
+	c = math.complex(-1, -1)
+	assert c.angle() * 180 / math.Pi == -135
+	mut cc := c.conjugate()
+	assert cc.angle() + c.angle() == 0
+}