Sin kata in Go

sin.go

package main

const accuracy = 0.00001

func multiplier(i int, angle, num, den float64) (float64, float64) {
	num *= angle * angle
	den *= float64(i * (i - 1))

	return num, den
}

func sin(angle float64) float64 {
	sign := 1.0
	val := angle
	num, den := angle, 1.0

	for i := 3; ; i += 2 {
		sign *= -1
		num, den = multiplier(i, angle, num, den)
		term := num / den

		if term < accuracy {
			break
		}

		val += sign * term
	}

	return val
}

sin_test.go

package main

import (
	"math"
	"testing"
)

var sinValues = []struct {
	rad, val float64
}{
	{0.0, 0.0},
	{math.Pi / 2, 1},
	{math.Pi / 4, 1 / math.Sqrt2},
	{math.Pi, 0},
}

func compare(x, y float64) bool {
	if math.Abs(x-y) < accuracy {
		return true
	}

	return false
}

func TestSineVal(t *testing.T) {
	for _, d := range sinValues {
		if val := sin(d.rad); !compare(val, d.val) {
			t.Errorf("Expected sin(%v) to be %v but got %v", d.rad, d.val, val)
		}
	}
}