Adding value to Scala map
dictionary, scala
Solution
This is an ambiguity caused by the similarity between the notation for tuples and the one for parameter lists :
`x + (1,0)` is notation for `x.+(1,0)` but sadly there is no method on `x` that takes two `Int` parameters. What you want is `x.+((1,0))`, i.e. `x + ((1,0))`.
There is something in Scala called auto-tupling, see this question and answers, which rewrites, for example, `println (1,2)` to `println((1,2))`. Except this will not work here because the `+` method takes a variable number of arguments and not a single one like `println`.
You get that strange error message because it expect every value in your parameter list `(1,0)` to be a tuple, as in `myMap + ((1,2), (1,3), (3,4))`. It finds an `Int` instead of a `(Int, Int)`, hence the error.
Problem
Why does this work: ``` val x = Map[Int,Int]() val y = (1, 0) x + y ``` but not this? ``` val x = Map[Int,Int]() x + (1, 0) ``` The error produced is: ``` <console>:11: error: type mismatch; found : Int(1) required: (Int, ?) x + (1,0) ^ ``` If I were to enter `(1,0)` into the REPL, it correctly types it as `(Int,Int)`. I should add that this works fine: ``` x + (1 -> 0) ```