Partial application

We use partial application when we want to "fix" some parameters of a given function, resulting in new functions

import org.funktionale.partials.*
//use explicit typing for clarity sake
val prefixAndPostfix: (String, String, String) -> String = {(prefix:String, x:String,postfix:String) -> "${prefix}${x}${postfix}"}  

val prefixAndBang: (String, String) -> String = prefixAndPostfix.partially3("!")

val hello: (String) -> String = prefixAndBang.partially1("Hello, ")

assertEquals(hello("funKTionale"),"Hello, funKTionale!")

Although partiallyX is explicit probably you want something more natural. funKTionale comes with several overloads for the invoke function that let you create partially applied functions in a more natural way using named parameters

import org.funktionale.partials.*
//use explicit typing for clarity sake
val prefixAndPostfix: (String, String, String) -> String = {(prefix:String, x:String,postfix:String) -> "${prefix}${x}${postfix}"}  

//passing just the third parameter will return a new function (String, String) -> String
val prefixAndBang: (String, String) -> String = prefixAndPostfix(p3 = "!")

//passing just the first parameter will return a new function (String) -> String
val hello: (String) -> String = prefixAndBang(p1 = "Hello, ")

assertEquals(hello("funKTionale"),"Hello, funKTionale!")