How do i 'curry' in scala

[Trilochan Bharadwaj]

Hi,

OK, first of all, I am admitting that I am not experienced with Scala at all, After buying Venkat's book, which I must admit is really hot! I tried a few things in first 4-5 chapters I guess (this is more of coding and less of reading ... ), anyways, I was able to intuitively (beauty of Scala?) do anonymous functions and invoke them, however i can't figure out how do i define a lambda expression so as to speak, or something which takes function as an argument or returns a function or both... the whole notation (I decided to not read by skipping chapters, (there's a functions chapter in the book ...), but couldn't resist doing it myself first =) .. I wrote this but it didn't compile:

val someFunctor = (i : (j : Int =>  j*j)  => print("i = " + i + "j = " + j););
// Now I understand this much that obviously (j : Int => j*j) is wrong =(

Any suggestions?

Trilochan

[Trilochan Bharadwaj]

OK, I searched this forum and got an excellent link:
Functions in Scala

[Garrett Rowe]

I'm not sure what you were going for, but as you saw in that blog posting, to define a method that takes a function argument you use either one of the following equivalent methods.

   def myMethod(func: String => Int): Unit = println(func("foo"))

   def myMethod2(func: Function2[String, Int]): Unit = println(func("foo"))

You can call it with either a named method, or by an anonymous function:

   def m(str: String): Int = str.length

   def callIt: Unit = {
      myMethod(m(_))
      myMethod(m) //equivalent to the above
      myMethod(s => s.hashCode) //anonymous function
   }

[Gabriel Claramunt]

Looks like currying is something different than what you where trying to accomplish.
Currying is simply the transformation of a function with multiple parameters into another function with only one parameter that returns a function of the remaining parameters.
In Scala, if you want to write curried functions, you just separate the parameters with parenthesis.
If the normal(uncurried) function is:

def f(x:Int,y:Int,z:Int)=...

then, the curried version is:

def f(x:Int)(y:Int)(z:Int)=...

A while ago, I did a blog entry on currying in Scala vs Haskell