scala - Using Tuples in map, flatmap,... partial functions

Question

If I do:

val l = Seq(("un", ""), ("deux", "hehe"), ("trois", "lol"))
l map { t => t._1 + t._2 }

It's ok.

If I do:

val l = Seq(("un", ""), ("deux", "hehe"), ("trois", "lol"))
l map { case (b, n) => b + n }

It's ok too.

But if I do:

val l = Seq(("un", ""), ("deux", "hehe"), ("trois", "lol"))
l map { (b, n) => b + n }

It will not work.
Why should I use "case" keyword to use named tuples?

Answer 1

The error message with 2.11 is more explanatory:

scala> l map { (b, n) => b + n }
<console>:9: error: missing parameter type
Note: The expected type requires a one-argument function accepting a 2-Tuple.
      Consider a pattern matching anonymous function, `{ case (b, n) =>  ... }`
              l map { (b, n) => b + n }
                       ^
<console>:9: error: missing parameter type
              l map { (b, n) => b + n }
                          ^

For an apply, you get "auto-tupling":

scala> def f(p: (Int, Int)) = p._1 + p._2
f: (p: (Int, Int))Int

scala> f(1,2)
res0: Int = 3

where you supplied two args instead of one.

But you don't get auto-untupling.

People have always wanted it to work that way.