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Multiple parameters lists, e.g. def foo(a:Int)(b:Int) = {} and multiple parameters per list, e.g. def foo(a:Int, b:Int) = {} are semantically equivalent so far as I can tell, and most functional languages have only one way of declaring multiple parameters, e.g. F#.
The only reason I can figure out for supporting both these styles of function definitions is to allow syntax-like language extensions using a parameter list that has only one parameter in it.
def withBufferedWriter(file: File)(block: BufferedWriter => Unit) can now be called with the syntax-looking
withBufferedWriter(new File("myfile.txt")) { out => out write "whatever" ... } However, there could be other ways of supporting the use of curly braces without having multiple parameter lists.
A related question: why is the use of multiple parameter lists in Scala called "currying"? Currying is usually defined as a technique for making an n-ary function unary for the sake of supporting partial application. However, in Scala one can partially apply a function without making a "curried" (multiple parameter lists with one param each) version of the function.
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Advantages of Currying Function in Scala One benefit is that Scala currying makes creating anonymous functions easier. Scala Currying also makes it easier to pass around a function as a first-class object. You can keep applying parameters when you find them.
=> is syntactic sugar for creating instances of functions. Recall that every function in scala is an instance of a class. For example, the type Int => String , is equivalent to the type Function1[Int,String] i.e. a function that takes an argument of type Int and returns a String .
Implicit parameters are the parameters that are passed to a function with implicit keyword in Scala, which means the values will be taken from the context in which they are called.
The Partially applied functions are the functions which are not applied on all the arguments defined by the stated function i.e, while invoking a function, we can supply some of the arguments and the left arguments are supplied when required.
It makes you able to do e.g.:
scala> def foo(as: Int*)(bs: Int*)(cs: Int*) = as.sum * bs.sum * cs.sum foo: (as: Int*)(bs: Int*)(cs: Int*)Int scala> foo(1, 2, 3)(4, 5, 6, 7, 9)(10, 11) res7: Int = 3906 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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