Kotlin’s extension functions provide you with a way of “adding” methods to a class, ... To create an extension function, write the name of the class or the type that you want to extend ...

In Kotlin, functions may be declared at top level in a file, locally inside other functions, ... To create a class instance, call the constructor just like a regular function.

In Kotlin, some functions can be called using predefined operators. ... Kotlin’s solution is to create what it calls a companion object, which is defined within the Fraction class.