Can someone explain why nums.map(+2) does not work but nums.map(2+) works?
scala> val nums=List(1,2,3,4)
nums: List[Int] = List(1, 2, 3, 4)
scala> nums.map(2+)
res3: List[Int] = List(3, 4, 5, 6)
scala> nums.map(+2)
<console>:27: error: type mismatch;
found : Int(2)
required: Int => ?
nums.map(+2)
^
Look at the signature for map():
final def map[B](f: (A) => B): List[B]
The argument, f, is a function from A to B. 2+ fulfills that function requirement because it is a syntactic shorthand for 2.+(_). In other words, the +() method invoked on an instance of the Int class, turned into a proper function via eta expansion.
If you want the + before the 2 then you can .map(_+2).
