Does Kotlin have UFCS? <https://en.m.wikipedia.org...

# language-proposals

[Arun]

Does Kotlin have UFCS? https://en.m.wikipedia.org/wiki/Uniform_Function_Call_Syntax I didn't find any related documentation. What would it take to support UFCS?

[hfhbd]

As far as I understand UFCS: It is called receiver in Kotlin: https://kotlinlang.org/docs/lambdas.html#function-literals-with-receiver
You can also create you own extension functions.

[mikehearn]

I think the idea of UFCS is that you don't need the extension function / receiver concept anymore. The first parameter just becomes specially privileged in the syntax, by convention.

[hfhbd]

you can call fun A.foo(b: B): C with foo(a, b)

[hfhbd]

the compiler converts a.foo(b) anyway 🙂

[xxfast]

UFCS sounds like this is the friend syntax from c++

[elizarov]

UFCS comes from a different philosophy. A philosophy in Kotlin is that the function's author determines how the function is supposed to used. You, as a function author, decide if you want your function to be used like foo(a, b), or as a a.foo(b). While the philosophy of UFCS is that this decision should be made by the caller.

[hfhbd]

But if you use a lambda, both calling options are possible. Why is this case different?

val foo = fun Int.(s: String) { }

foo(42, "")
42.foo("")

[elizarov]

That was done to simplify lambda types hierarchy, so that they are all interchangeable.