CODEWITHSUNDEEP
iosswift
Quinton Pryce
Quinton Pryce

Reputation: 33

Can you set a variable equal to a function with a default parameter, using first class functions?

I want to save a function that takes two parameters as a function that only takes one parameter. I know I learned this with functional programming but I can't remember the methodology name or how to implement it.

Example: a methods like this:

func add (a: Int, b: Int) {
    return a + b
}

And you can manipulate and save a new method that let’s say only increments a by 1:

let increment = add(b:1)

print(increment(a: 4))
// prints 5

Can you do this in swift?

Upvotes: 0

Views: 85

Answers (2)

RajeshKumar R
RajeshKumar R

Reputation: 15768

You are looking for Default Parameter Values

You can assign default values to the parameters. When calling this function if you pass the value to the parameters that passed value will be used else the default value will be used. To use the default value you can avoid the parameter in the function calling

func add(a: Int = 1, b: Int = 1) -> Int {
    return a + b
}

print(add(a: 5, b: 5))//prints 10
print(add(a: 4))//prints 5
print(add(b: 4))//prints 5
print(add())//prints 2

Upvotes: 0

marosoaie
marosoaie

Reputation: 2371

It seems you're looking for function currying. This was a part of swift in earlier versions but was removed because it added too much complexity inside the compiler. (Like seen here: https://github.com/apple/swift-evolution/blob/master/proposals/0002-remove-currying.md)

I guess the closest you can get to a curried function is if you do something like this: 

func add(_ x: Int) -> (Int) -> Int {
    return { y in
        y + x
    }
}

With this you can say:

let add2 = add(2)
print(add2(3)) // prints 5

Upvotes: 3

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