Exploring Kotlin: Varargs and Infix Calls

You have certainly encountered these terms before, at least when you wanted to run your program or when you were inserting something into a hashmap.

Exploring Kotlin: Varargs and Infix Calls

Kotlin offers several advanced features that make code more expressive and concise. Two such features are varargs and infix calls. In this article, we’ll explore these features and compare them to their Java counterparts.

Varargs in Kotlin

varargs (variable-length arguments) allow a function to accept a variable number of arguments. This is particularly useful when you don’t know beforehand how many arguments will be passed to the function.

Kotlin Example

In Kotlin, you define a varargs parameter by using the vararg keyword. Here’s an example:

fun printAll(vararg messages: String) {
    for (message in messages) {
        println(message)
    }
}

fun main() {
    printAll("Hello", "World", "Kotlin", "Varargs")
}

Infix Calls in Kotlin

Infix calls allow functions with a single parameter to be called without using parentheses or the dot notation. This can make the code more readable, especially when defining custom operators.

Kotlin Example

To define an infix function in Kotlin, use the infix keyword. Here’s an example:

infix fun Int.times(str: String) = str.repeat(this)

fun main() {
    val result = 2 times "Hello "
    println(result)
}

In this example, times is an infix function that repeats a string a given number of times. It’s called using the infix notation 2 times "Hello ".

Another usage of infix call:

class Pack<T,S>(
    val i1: T,
    val i2: S,
){
    fun putTogether() = "$i1 $i2"
}

infix fun <T,S> T.pack(other:S) = Pack(this, other)

class VarargsClassMain {}

fun main(array: Array<String>) {
    val list = listOf("args: ", *array)
    println(list)
    val test: Pack<String, String> = "Hello" pack "World"
    println(test.putTogether())
}

The Pack class and pack infix function provide a flexible and readable way to combine two values of different types into a single object, with an easy-to-use concatenation method.

Benefits of Kotlin’s Features

Varargs: Kotlin’s vararg provides a concise way to define functions that accept a variable number of arguments, similar to Java but with a more readable syntax.
Infix Calls: Infix calls in Kotlin can make the code more readable and expressive, especially when creating DSLs (Domain-Specific Languages).

Conclusion

Kotlin’s varargs and infix calls are powerful features that enhance the readability and expressiveness of the code. While Java offers similar functionality with varargs, it lacks the elegant infix call syntax. These features, among others, contribute to Kotlin’s growing popularity as a modern, expressive language for the JVM.

Exploring Kotlin: Varargs and Infix Calls