调用咖喱函数

debugcn 发表于 Dev

蓝天

以下是curried函数的实现：

scala> def multiply(x: Int, y: Int) = x * y
multiply: (x: Int, y: Int)Int

scala> def multiplyCurried = (multiply _).curried
multiplyCurried: Int => (Int => Int)

当我尝试实现multipliCurried时，我收到异常：

<console>:10: error: missing parameter type
              multiplyCurried(a => b => a * b)

调用multipleCurried的正确实现是什么？

麦克斯

摘自Wikipedia：Currying是一种将对带有多个参数（或参数元组）的函数的求值转换为对函数序列进行求值的技术，每个函数都具有一个参数（部分应用程序）

def multiply(x: Int, y: Int) = x * y          //> multiply: (x: Int, y: Int)Int

def multiplyCurried = (multiply _).curried    //> multiplyCurried: => Int => (Int => Int)

def multiplyCurried2(x: Int)(y: Int) = x * y  //> multiplyCurried2: (x: Int)(y: Int)Int

def multiplyCurried3(x:Int) = (y:Int) => x * y //> multiplyCurried3: (x: Int)Int => Int

def multiplyCurried4 = multiplyCurried2 _ //> multiplyCurried4: => Int => (Int => Int)

multiply(1, 2)                                //> res1: Int = 2
multiplyCurried(1)(2)                         //> res2: Int = 2
multiplyCurried2(1)(2)                        //> res3: Int = 2
multiplyCurried3(1)(2)                        //> res4: Int = 2

multiplyCurried2只是语法糖multiplyCurried3。

维克多正确地指出的意见，multiplyCurried而multiplyCurried2实际上是不一样的。的实现multiplyCurried4包含将配方变成multiplyCurried2基本上等于的功能的配方multiplyCurried。

currying的优点是部分应用程序：

val m = multiplyCurried(1)                    //> m  : Int => Int = <function1>
m(2)                                           //> res5: Int = 2
val m2 = multiplyCurried2(1)_                 //> m  : Int => Int = <function1>
m2(2) 

                                    //> res6: Int = 2

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