Scala学习——函数

逃离我推掉我的手 2023-07-09 07:25 11阅读 0赞

## Scala学习——函数 ##

### 一、方法的定义和使用 ###

**1.函数的定义如下：**

**def  sum(x:Int, y:Int) : Int = \{**

**    x+y**

**\}**

(1)以def开头定义

(2)def后面跟函数名

(3)括号中的参数列表，必须指定类型。

(4)冒号后跟函数返回值类型

(5)=后跟大括号内的函数体

**2.函数/方法的定义**

def 方法名 (参数名：参数类型) : 返回值类型\{

大括号内为方法体

方法体内最后一行为返回值，不用return

**3.示例1：求两个数字的和**

def sum(x:Int, y:Int): Int={
        x + y
      }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70][]

**4.求两个数字中的最大值**

def max(x:Int, y:Int): Int={
        if (x>y) x
        else y

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 1][]

**5.没有参数的方法，可以省略调用的括号**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 2][]

**6.没有返回值**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 3][]

### 二、默认参数 ###

1.计算圆的面积

def area(pai:Double=3.14,r:Double):Double={
          pai*r*r
        }

注意问题：

(1)参数如果不指定名字，必须按照顺序传递。

(2)如果指定了名字，可以不按照顺序传递。

(3)默认参数在不传递新的值时才生效，如果指定新的pai，将会覆盖原始的值。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 4][]

### 三、可变参数 ###

**使用\*来表示可以传递任意数量的参数。**

**1.定义求和函数**

def sum(nums:Int*)={
        var result = 0
        for (num <- nums){
          result += num
        }
        result
      }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 5][]

**2.计算票价**

(1)方法一

def price(age:Int,price:Int=120) = {
        if (age <=8)
          println("免票\n")
        else if (age>8 & age<18)
          printf("票价为:%.2f元\n",price*0.5)
        else if (age>=18 & age<60)
          printf("票价为：%.2f元\n",price*1.0)
        else printf("票价为:%.2f元\n",price*0.5)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 6][]

(2)方法二

def price(age:Int,price:Int=120) = {
        if (age <=8)
          price*0.0
        else if (age>8 & age<18)
          price*0.5
        else if (age>=18 & age<60)
          price*1.0
        else price*0.5

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 7][]

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