feat: add mathutil package

mathutil/mathutil.go

@@ -0,0 +1,92 @@
+// Copyright 2021 dudaodong@gmail.com. All rights reserved.
+// Use of this source code is governed by MIT license
+
+// Package mathutil implements some functions for math calculation.
+package mathutil
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+)
+
+// Exponent calculate x^n
+func Exponent(x, n int64) int64 {
+	if n == 0 {
+		return 1
+	}
+
+	t := Exponent(x, n/2)
+
+	if n%2 == 1 {
+		return t * t * x
+	}
+
+	return t * t
+}
+
+// Fibonacci calculate fibonacci number before n
+func Fibonacci(first, second, n int) int {
+	if n <= 0 {
+		return 0
+	}
+	if n < 3 {
+		return 1
+	} else if n == 3 {
+		return first + second
+	} else {
+		return Fibonacci(second, first+second, n-1)
+	}
+}
+
+// Factorial calculate x!
+func Factorial(x uint) uint {
+	var f uint = 1
+	for ; x > 1; x-- {
+		f *= x
+	}
+	return f
+}
+
+// Percent calculate the percentage of val to total
+func Percent(val, total float64, n int) float64 {
+	if total == 0 {
+		return float64(0)
+	}
+	tmp := val / total * 100
+	res := RoundToFloat(tmp, n)
+
+	return res
+}
+
+// RoundToString round up to n decimal places
+func RoundToString(x float64, n int) string {
+	tmp := math.Pow(10.0, float64(n))
+	x *= tmp
+	x = math.Round(x)
+	res := strconv.FormatFloat(x/tmp, 'f', n, 64)
+	return res
+}
+
+// RoundToFloat round up to n decimal places
+func RoundToFloat(x float64, n int) float64 {
+	tmp := math.Pow(10.0, float64(n))
+	x *= tmp
+	x = math.Round(x)
+	return x / tmp
+}
+
+// TruncRound round off n decimal places
+func TruncRound(x float64, n int) float64 {
+	floatStr := fmt.Sprintf("%."+strconv.Itoa(n+1)+"f", x)
+	temp := strings.Split(floatStr, ".")
+	var newFloat string
+	if len(temp) < 2 || n >= len(temp[1]) {
+		newFloat = floatStr
+	} else {
+		newFloat = temp[0] + "." + temp[1][:n]
+	}
+	res, _ := strconv.ParseFloat(newFloat, 64)
+	return res
+}

mathutil/mathutil_test.go

@@ -0,0 +1,61 @@
+package mathutil
+
+import (
+	"testing"
+
+	"github.com/duke-git/lancet/internal"
+)
+
+func TestExponent(t *testing.T) {
+	assert := internal.NewAssert(t, "TestExponent")
+
+	assert.Equal(int64(1), Exponent(10, 0))
+	assert.Equal(int64(10), Exponent(10, 1))
+	assert.Equal(int64(100), Exponent(10, 2))
+}
+
+func TestFibonacci(t *testing.T) {
+	assert := internal.NewAssert(t, "TestFibonacci")
+
+	assert.Equal(0, Fibonacci(1, 1, 0))
+	assert.Equal(1, Fibonacci(1, 1, 1))
+	assert.Equal(1, Fibonacci(1, 1, 2))
+	assert.Equal(5, Fibonacci(1, 1, 5))
+}
+
+func TestFactorial(t *testing.T) {
+	assert := internal.NewAssert(t, "TestFactorial")
+
+	assert.Equal(uint(1), Factorial(0))
+	assert.Equal(uint(1), Factorial(1))
+	assert.Equal(uint(2), Factorial(2))
+	assert.Equal(uint(6), Factorial(3))
+}
+
+func TestPercent(t *testing.T) {
+	assert := internal.NewAssert(t, "TestPercent")
+
+	assert.Equal(float64(50), Percent(1, 2, 2))
+	assert.Equal(float64(33.33), Percent(0.1, 0.3, 2))
+}
+
+func TestRoundToFloat(t *testing.T) {
+	assert := internal.NewAssert(t, "TestRoundToFloat")
+
+	assert.Equal(RoundToFloat(0, 0), float64(0))
+	assert.Equal(RoundToFloat(0, 1), float64(0))
+	assert.Equal(RoundToFloat(0.124, 2), float64(0.12))
+	assert.Equal(RoundToFloat(0.125, 2), float64(0.13))
+	assert.Equal(RoundToFloat(0.125, 3), float64(0.125))
+	assert.Equal(RoundToFloat(33.33333, 2), float64(33.33))
+}
+
+func TestRoundToString(t *testing.T) {
+	assert := internal.NewAssert(t, "TestRoundToString")
+
+	assert.Equal(RoundToString(0, 0), "0")
+	assert.Equal(RoundToString(0, 1), "0.0")
+	assert.Equal(RoundToString(0.124, 2), "0.12")
+	assert.Equal(RoundToString(0.125, 2), "0.13")
+	assert.Equal(RoundToString(0.125, 3), "0.125")
+}