Currying

curry.go

package main

type VarSum func(a ...int) interface{}

func curry(fn func(x, y, z int) int, args ...int) interface{} {
	if len(args) >= 3 {
		return fn(args[0], args[1], args[2])
	}
	return VarSum(func(more ...int) interface{} {
		args = append(args, more...)
		return curry(fn, args...)
	})
}

func sum(a, b, c int) int {
	return a + b + c
}

func main() {
	{
		c := curry(sum).(VarSum)
		c1 := c(1).(VarSum)
		c2 := c1(2).(VarSum)
		c3 := c2(3).(int)
		println(c3)
	}
	{
		c := curry(sum).(VarSum)
		c1 := c(1).(VarSum)
		c2 := c1(2, 3).(int)
		println(c2)
	}
	{
		c := curry(sum).(VarSum)
		c1 := c(1).(VarSum)
		c2 := c1(2).(VarSum)
		c3 := c2(3, 4).(int)
		println(c3)
	}
}

curry.js

const curry = (fn, ...args) =>
	(args.length >= fn.length) ?
		fn(...args.slice(0, fn.length)) :
		(...more) => curry(fn, ...args, ...more)

const sum = (a, b, c) => a + b + c


curried = curry(sum)
console.log(curried(1)(2)(3))
console.log(curried(1)(2, 3))
console.log(curried(1)(2, 3, 4)) // 4 will be ignored