Infix Notation : Kotlin

Suneet Agrawal
2 min readOct 6, 2018


Ever imagined calling a public function of a class without dot and parentheses of the parameter in Kotlin. Kotlin provides infix notation with which we can call a function with the class object without using a dot and parentheses across the parameter. Using infix function provides more readability to a function similar to other operators like in, is, as in Kotlin.

This post was originally posted at and reposted on Medium on 7th Oct 2018.

To make a function infix notation enabled, add infix keyword before the function.

infix fun Int.add(b : Int) : Int = this + bval x = 10.add(20)
val y = 10 add 20 // infix call

But an Infix function must satisfy the following requirements

  • They must be member functions or extension functions.
  • They must have a single parameter.
  • The parameter must not accept a variable number of arguments and must have no default value.

What if I use an infix function with other operators.

You can but you should keep the priority of the operator in mind.

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Reference: Kotlin docs



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