Example
There are two ways to define functions with multiple parameters in F#, Curried functions and Tupled functions.
let curriedAdd x y = x + y // Signature: x:int -> y:int -> int
let tupledAdd (x, y) = x + y // Signature: x:int * y:int -> int
All functions defined from outside F# (such as the .NET framework) are used in F# with the Tupled form. Most functions in F# core modules are used with Curried form.
The Curried form is considered idiomatic F#, because it allows for partial application. Neither of the following two examples are possible with the Tupled form.
let addTen = curriedAdd 10 // Signature: int -> int
// Or with the Piping operator
3 |> curriedAdd 7 // Evaluates to 10
The reason behind that is that the Curried function, when called with one parameter, returns a function. Welcome to functional programming !!
let explicitCurriedAdd x = (fun y -> x + y) // Signature: x:int -> y:int -> int
let veryExplicitCurriedAdd = (fun x -> (fun y -> x + y)) // Same signature
You can see it is exactly the same signature.
However, when interfacing with other .NET code, as in when writing libraries, it is important to define functions using the Tupled form.
