Scala - Currying and default arguments

Question

I have a function with two parameter lists that I am trying to partially apply and use with currying. The second parameter list contains arguments that all have default valu

Answer 1

The type inference engine gives to partial the type of what comes next; i.e., the eta expansion test(1) _. You can see e.g. in the REPL that partial has type (Int, Int) => Unit, whereas test has type (a: Int)(b: Int,c: Int)Unit. The result of the eta expansion is a Function object, which does not carry any argument names with it (as it is possible to define Function with anonymous parameters).

To fix this, you have to define partial as follows:

def partial(b: Int = 2, c: Int = 3) = test(1)(b,c)

Maybe you'll want to factor out the default values where both test and partial can reach them to make sure they stay equal. But I know of no trick to avoid repeating the names of the parameters without introducing extra overhead like creating of new objects, etc.