How Can You Achieve Partial Application and Function Currying in Go?

Currying in Go

In functional programming, currying is a technique for transforming a function that takes multiple arguments into a series of nested functions that each take a single argument. This allows for partial application, where a function can be applied to a subset of its arguments to produce a new function that takes the remaining arguments.

Partial Application in Go

Partial application is not directly supported in Go, but it can be achieved using closures. A closure is a function that retains access to the variables of its enclosing scope even after the scope has exited. By returning a closure from a function, we can create a partially applied function.

For example, the following function returns a closure that adds a given number to its input:

func add(a int) func(b int) int {
    return func(b int) int {
        return a + b
    }
}

We can then use this closure to partially apply the add function:

add2 := add(2)
fmt.Println(add2(3)) // prints 5

Function Currying in Go

Function currying can also be achieved in Go using closures. The following function curries a function that takes multiple arguments:

func curry(f func(...int) int) func(int) func(...int) int {
    return func(a int) func(...int) int {
        return func(b... int) int {
            args := append([]int{a}, b...)
            return f(args...)
        }
    }
}

This function returns a function that takes one argument and returns a new function that takes the remaining arguments. We can then use this function to curry any function:

add := curry(func(a, b, c int) int { return a + b + c })
add2 := add(2)
add3 := add3(3)
fmt.Println(add3(4)) // prints 9

Conclusion

While Go does not natively support partial application or function currying, these techniques can be achieved using closures. This allows Go programmers to take advantage of the functional programming concepts of partial application and currying, even though the language itself does not provide direct support for them.

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