Code golf for function composition

codegolf.go

package main

import (
	"fmt"
)

type fn func(int) int

func combine(fns ...fn) fn {
	return func(x int) int {
		res := x
		for _, f := range fns {
			res = f(res)
		}
		return res
	}
}

func main() {
	addThree := func(x int) int { return x + 3 }
	multiplyByTwo := func(x int) int { return x * 2 }
	combined := combine(addThree, addThree, multiplyByTwo, multiplyByTwo)
	fmt.Println(combined(12))
}

codegolf.java

interface fn extends Function<Double,Double>{}

fn addThree = x -> x+3;

fn multiplyByTwo = x -> x*2;

interface fns extends Function<Stream<fn>,Optional<fn>>{}

fns combine = fncs -> fncs.reduce((f,g)-> x -> g.apply(f.apply(x)));

var fun = combine.apply(Stream.of(addThree,addThree,multiplyByTwo,multiplyByTwo)).get();

fun.apply(12.0);

codegolf.js

let addThree = x => x+3
let multiplyByTwo = x => x*2

let combine = funcs => funcs.reduce((f,g) => x => g(f(x)))

let fun = combine([addThree,addThree,multiplyByTwo,multiplyByTwo])

fun(12)

codegolf.py

from typing import Callable


def addThree(x: float) -> float:
    return x + 3


def multiplyByTwo(x: float) -> float:
    return x * 2

ComposableFunction = Callable[[float], float]
def compose(*functions: ComposableFunction) -> ComposableFunction:
    return functools.reduce(lambda f,g: lambda x: g(f(x)), functions)


def funcDemo():
    x = 12
    myfunc = compose(addThree, addThree, multiplyByTwo, multiplyByTwo)
    result = myfunc(12)
    print(f"Result: {result}")


# Press the green button in the gutter to run the script.
if __name__ == '__main__':
    funcDemo()