map += foo is shorthand for:
map.+=(foo)
Thus,
map += (1, "Some String") is an attempt to call:
map.+=(1, "Some String")
map has no method that accepts an Int and a String, though it does
have a method that accepts a tuple of Int and String.
Yes, it's sad that the two mechanisms are not interchangeable.
2008/10/8 Lorenz Bateman <
lorenzb@...>:
> I've been reading the scala eBook and found an example of adding a key value
> pair to a map:
>
> map += (1 -> "Some String")
>
> it seems that the (1 -> "Some String") results in a Tuple2, however the (1,
> "Some String") also results in a Tuple2, as follows:
>
> scala> 1 -> "Some String"
> res8: (Int, java.lang.String) = (1,Some String)
>
> scala> res8 getClass
> res10: java.lang.Class[_] = class scala.Tuple2
>
> scala> (1, "Some String")
> res11: (Int, java.lang.String) = (1,Some String)
>
> scala> res11 getClass
> res12: java.lang.Class[_] = class scala.Tuple2
>
> The problem I have is understanding why map += (1 -> "Some String") works
> fine, but:
>
> scala> map += (1, "Some String")
> <console>:6: error: type mismatch;
> found : Int(1)
> required: (Int, String)
> map += (1, "Some String")
> ^
>
> gives me an error.
>
> Thanks
>
> Lorenz
>
