How to specify typical types of ducks (implicit interface) in Kotlin?

Question

for instance

// Not valid Kotlin code.
fun <T : Summable> myFunction ...

T : Summablemeans that any type Tsupports the operator +, i.e. has a method .plus.

Answer 1

There is no such function in Kotlin, and at present it is not planned for a future release.

Answer 2

You can take a look at the DucKtypes project on GitHub, which allows you to use "static ducktyping". For instance:

interface Summable { fun plus() }
object x { fun plus(){ println("plus") } } 
fun myFunction( s : Summable ){ s.plus() }
myFunction( x )

The project is still fairly new, but gradle -plugin may soon be launched to automate code generation.