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Scala Type Inference

Name: Anonymous 2012-10-27 0:24

Does anyone know the details why?



def map[T, U](a: List[T], f: (T) => U): List[U] =

  for (e <- a) yield f(e)

  

def map0[T, U](a: List[T])(f: (T) => U): List[U] =

  for (e <- a) yield f(e)

 

// type parameter necessary

map(List(1,2,3), (x: Int) => x.toString)

  

// type parameter not necessary

map0(List(1,2,3))(_.toString)

Name: Anonymous 2012-10-27 1:08

it shouldn't be necessary. All these hipster languages want to type inference to be cool but can't quite do it right.



# let rec map__ a f = match a with [] -> [] | x::xs -> f(x)::(map__ xs f);;

val map__ : 'a list -> ('a -> 'b) -> 'b list = <fun>

# map__ [1; 2; 3; 4; 5] ( ( * ) 2);;

- : int list = [2; 4; 6; 8; 10]

# let rec map___ (a,f) = match a with [] -> [] | x::xs -> f(x)::(map___(xs,f));;

val map___ : 'a list * ('a -> 'b) -> 'b list = <fun>

# map___([1; 2; 3; 4; 5], ( ( * ) 2));;

- : int list = [2; 4; 6; 8; 10]

Name: Anonymous 2012-10-27 6:22

Scala
obsoleted by http://en.wikipedia.org/wiki/C%2B%2B0x

Name: sage 2012-10-27 6:28

>>3
All I read was
c BB

$ exit

Name: Anonymous 2012-10-27 7:01

>>2

Ya I just played around with Haskell and Ocaml. They're type inference is on a another level.

Name: Anonymous 2012-10-27 7:03

>>5
They're

What the fuck am I doing

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Scala Type Inference

1 Name: Anonymous 2012-10-27 0:24

2 Name: Anonymous 2012-10-27 1:08

3 Name: Anonymous 2012-10-27 6:22

4 Name: sage 2012-10-27 6:28