Scala function Corialization (Currying)

Example

First, let’s define a function:

def add(x:Int,y:Int)=x+y

So when we apply it, we should use it like this: add(1,2)

Now let’s transform this function:

def add(x:Int)(y:Int) = x + y

So when we apply it, we should use it like this: add(1)(2) in the end, the result is all the same, which is called Corialization.

Realization process

add(1)(2) in fact, two ordinary functions (non-Corialized functions) arecalled in turn, the first call takes a parameter x and returns a value of afunction type, and the second call uses the parameter y to call the value of this function type.

In essence, it first evolved into such a method:

def add(x:Int)=(y:Int)=>x+y

So what does this function mean? Receives an x as an argument and returns ananonymous function defined as receiving a Int type parameter y, the body of the function is x+y . Now let’s call this method.

val result = add(1)

Returns a result , result should be an anonymous function (y:Int)=>1+y

So in order to get the results, we continue to call the result .

val sum = result(2)

The final printed result is 3.

Complete instance

Here is a complete example:

object Test {
   def main(args: Array[String]) {
      val str1:String = "Hello, "
      val str2:String = "Scala!"
      println( "str1 + str2 = " +  strcat(str1)(str2) )
   }

   def strcat(s1: String)(s2: String) = {
      s1 + s2
   }
}

Execute the above code, and the output is as follows:

$ scalac Test.scala
$ scala Test
str1 + str2 = Hello, Scala!