Is trait extends (A => B) a trait extending function?

Question

The following trait Parser[+T] is a trait that extends a function that accepts an Input and returns a Result[T] .

 trait Parser[+T] extends (Input => Result[T])

Is that correct?

Answer 1

Right.

Input => Result[T] is a shortcut for Function1[Input, Result[T]] . It has an abstrat method

def apply(v1: Input) : Result[T]

which when defined will be the actual function implementation.

Scala syntax allows methods called apply to be called silently, that is for some expression e , e(x1, ... xn) will be translated to e.apply(x1, ... xn)

Answer 2

Almost. It extends Function[Input, Result[T]] - the type of function that takes Input as argument and returns Result[T] (not T ) as result. Result[T] carries information about a successful parse into a T or an error that occurs during parse.