Scala - Currying Functions

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Currying transforms a function that takes multiple parameters into a chain of functions, each taking a single parameter. Curried functions are defined with multiple parameter lists, as follows −

Syntax

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

Alternatively, you can also use the following syntax to define a curried function −

Syntax

def strcat(s1: String) = (s2: String) => s1 + s2

Following is the syntax to call a curried function −

Syntax

strcat("foo")("bar")

You can define more than two parameters on a curried function based on your requirement. Try the following example program to show currying concept.

Example

object Demo {
   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
   }
}

Save the above program in Demo.scala. The following commands are used to compile and execute this program.

Command

\>scalac Demo.scala
\>scala Demo

Output

str1 + str2 = Hello, Scala!