If I have:
val f : A => B => C
This is shorthand for:
val f : Function1[A, Function1[B, C]]
How do I get a function g
with the signature:
val g : (A, B) => C = error("todo")
(i.e.)
val g : Function2[A, B, C] //or possibly
val g : Function1[(A, B), C]
in terms of f
?
=> is syntactic sugar for creating instances of functions. Recall that every function in scala is an instance of a class. For example, the type Int => String , is equivalent to the type Function1[Int,String] i.e. a function that takes an argument of type Int and returns a String .
scala> val f : Int => Int => Int = a => b => a + b
f: (Int) => (Int) => Int = <function1>
scala> Function.uncurried(f)
res0: (Int, Int) => Int = <function2>
Extending retonym's answer, for completeness
val f : Int => Int => Int = a => b => a + b
val g: (Int, Int) => Int = Function.uncurried(f)
val h: ((Int, Int)) => Int = Function.tupled(g)
The converse functions for both of these operations are also provided on the Function object, so you could write the above backwards, if you wished
val h: ((Int, Int)) => Int = x =>(x._1 + x._2)
val g: (Int, Int) => Int = Function.untupled(h)
val f : Int => Int => Int = g.curried //Function.curried(g) would also work, but is deprecated. Wierd
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