# Mathutil
mathutil包实现了一些数学计算的函数.

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## 源码:

- [https://github.com/duke-git/lancet/blob/main/mathutil/mathutil.go](https://github.com/duke-git/lancet/blob/main/mathutil/mathutil.go)


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## 用法:
```go
import (
    "github.com/duke-git/lancet/v2/mathutil"
)
```

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## 目录
- [Average](#Average)
- [Exponent](#Exponent)
- [Fibonacci](#Fibonacci)
- [Factorial](#Factorial)
- [Max](#Max)
- [MaxBy](#MaxBy)
- [Min](#Min)
- [MinBy](#MaxBy)
- [Percent](#Percent)
- [RoundToFloat](#RoundToFloat)
- [RoundToString](#RoundToString)
- [TruncRound](#TruncRound)

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## Documentation


### <span id="Average">Average</span>
<p>计算平均数. 可能需要对结果调用RoundToFloat方法四舍五入</p>

<b>函数签名:</b>

```go
func Average[T lancetconstraints.Number](numbers ...T) T
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.Average(0, 0)) //0
	fmt.Println(mathutil.Average(1, 1)) //1
	avg := mathutil.Average(1.2, 1.4) //1.2999999998
	roundAvg := mmathutil.RoundToFloat(avg, 1) // 1.3
}
```


### <span id="Exponent">Exponent</span>
<p>指数计算（x的n次方）</p>

<b>函数签名:</b>

```go
func Exponent(x, n int64) int64
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.Exponent(10, 0)) //1
	fmt.Println(mathutil.Exponent(10, 1)) //10
	fmt.Println(mathutil.Exponent(10, 2)) //100
}
```



### <span id="Fibonacci">Fibonacci</span>
<p>计算斐波那契数列的第n个数</p>

<b>函数签名:</b>

```go
func Fibonacci(first, second, n int) int
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.Fibonacci(1, 1, 1)) //1
	fmt.Println(mathutil.Fibonacci(1, 1, 2)) //1
	fmt.Println(mathutil.Fibonacci(1, 1, 3)) //2
	fmt.Println(mathutil.Fibonacci(1, 1, 4)) //3
	fmt.Println(mathutil.Fibonacci(1, 1, 5)) //5
}
```



### <span id="Factorial">Factorial</span>
<p>计算阶乘</p>

<b>函数签名:</b>

```go
func Factorial(x uint) uint
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.Factorial(0)) //1
	fmt.Println(mathutil.Factorial(1)) //1
	fmt.Println(mathutil.Factorial(2)) //2
	fmt.Println(mathutil.Factorial(3)) //6
}
```


### <span id="Max">Max</span>
<p>返回参数中的最大数</p>

<b>函数签名:</b>

```go
func Max[T lancetconstraints.Number](numbers ...T) T
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.Max(0, 0)) //0
	fmt.Println(mathutil.Max(1, 2, 3)) //3
	fmt.Println(mathutil.Max(1.2, 1.4, 1.1, 1.4)) //1.4
}
```



### <span id="MaxBy">MaxBy</span>
<p>使用给定的比较器函数返回切片的最大值</p>

<b>函数签名:</b>

```go
func MaxBy[T any](slice []T, comparator func(T, T) bool) T 
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	res1 := mathutil.MaxBy([]string{"a", "ab", "abc"}, func(v1, v2 string) bool {
		return len(v1) > len(v2)
	})
	fmt.Println(res1) //abc

	res2 := mathutil.MaxBy([]string{"abd", "abc", "ab"}, func(v1, v2 string) bool {
		return len(v1) > len(v2)
	})
	fmt.Println(res2) //abd

	res3 := mathutil.MaxBy([]string{}, func(v1, v2 string) bool {
		return len(v1) > len(v2)
	})
	fmt.Println(res3) //“”
}
```




### <span id="Min">Min</span>
<p>返回参数中的最小数</p>

<b>函数签名:</b>

```go
func Min[T lancetconstraints.Number](numbers ...T) T
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.Min(0, 0)) //0
	fmt.Println(mathutil.Min(1, 2, 3)) //1
	fmt.Println(mathutil.Min(1.2, 1.4, 1.1, 1.4)) //1.1
}
```



### <span id="MinBy">MinBy</span>
<p>使用给定的比较器函数返回切片的最小值</p>

<b>函数签名:</b>

```go
func MinBy[T any](slice []T, comparator func(T, T) bool) T 
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	res1 := mathutil.MinBy([]string{"a", "ab", "abc"}, func(v1, v2 string) bool {
		return len(v1) < len(v2)
	})
	fmt.Println(res1) //a

	res2 := mathutil.MinBy([]string{"ab", "ac", "abc"}, func(v1, v2 string) bool {
		return len(v1) < len(v2)
	})
	fmt.Println(res2) //ab

	res3 := mathutil.MinBy([]string{}, func(v1, v2 string) bool {
		return len(v1) < len(v2)
	})
	fmt.Println(res3) //“”
}
```




### <span id="Percent">Percent</span>
<p>计算百分比，保留n位小数</p>

<b>函数签名:</b>

```go
func Percent(val, total float64, n int) float64
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.Percent(1, 2, 2)) //1
	fmt.Println(mathutil.Percent(0.1, 0.3, 2)) //33.33
}
```



### <span id="RoundToFloat">RoundToFloat</span>
<p>四舍五入，保留n位小数</p>

<b>函数签名:</b>

```go
func RoundToFloat(x float64, n int) float64
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.RoundToFloat(0, 0)) //0
	fmt.Println(mathutil.RoundToFloat(0, 1)) //0
	fmt.Println(mathutil.RoundToFloat(0.124, 2)) //0.12
	fmt.Println(mathutil.RoundToFloat(0.125, 2)) //0.13
	fmt.Println(mathutil.RoundToFloat(0.125, 3)) //0.125
}
```




### <span id="RoundToString">RoundToString</span>
<p>四舍五入，保留n位小数，返回字符串</p>

<b>函数签名:</b>

```go
func RoundToString(x float64, n int) string
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.RoundToString(0, 0)) //"0"
	fmt.Println(mathutil.RoundToString(0, 1)) //"0.0:
	fmt.Println(mathutil.RoundToString(0.124, 2)) //"0.12"
	fmt.Println(mathutil.RoundToString(0.125, 2)) //"0.13"
	fmt.Println(mathutil.RoundToString(0.125, 3)) //"0.125"
}
```



### <span id="TruncRound">TruncRound</span>
<p>截短n位小数（不进行四舍五入）</p>

<b>函数签名:</b>

```go
func TruncRound(x float64, n int) float64
```
<b>例子:</b>

```go
package main

import (
    "fmt"
    "github.com/duke-git/lancet/v2/mathutil"
)

func main() {
	fmt.Println(mathutil.TruncRound(0, 0)) //0
	fmt.Println(mathutil.TruncRound(0, 1)) //0
	fmt.Println(mathutil.TruncRound(0.124, 2)) //0.12
	fmt.Println(mathutil.TruncRound(0.125, 2)) //0.12
	fmt.Println(mathutil.TruncRound(0.125, 3)) //0.125
}
```