andThen for function of two arguments in Scala
function, scala
Solution
It doesn't compile because `andThen` is a method of `Function1` (a function of one parameter: see the scaladoc).
Your function `f` has two parameters, so would be an instance of `Function2` (see the scaladoc).
To get it to compile, you need to transform `f` into a function of one parameter, by tupling:
scala> val h = f.tupled andThen g
h: (Int, Int) => String = <function1>
test:
scala> val t = (1,1)
scala> h(t)
res1: String = 2
You can also write the call to `h` more simply because of auto-tupling, without explicitly creating a tuple (although auto-tupling is a little controversial due to its potential for confusion and loss of type-safety):
scala> h(1,1)
res1: String = 2
Problem
Suppose I have two functions `f` and `g`: ``` val f: (Int, Int) => Int = _ + _ val g: Int => String = _ + "" ``` Now I would like to compose them with `andThen` to get a function `h` ``` val h: (Int, Int) => String = f andThen g ``` Unfortunately it doesn't compile :( ``` scala> val h = (f andThen g) <console> error: value andThen is not a member of (Int, Int) => Int val h = (f andThen g) ``` Why doesn't it compile and how can I compose `f` and `g` to get `(Int, Int) => String` ?