⚠️ Warning: This is a draft ⚠️

This means it might contain formatting issues, incorrect code, conceptual problems, or other severe issues.

If you want to help to improve and eventually enable this page, please fork RosettaGit's repository and open a merge request on GitHub.

This is almost the same as the code on the [[First-class_functions/Use_numbers_analogously#Go|main page]] except that the "empty interface" (interface{}) has been dropped in favour of a newly defined interface type and a pair of simple implementations of that interface.

This is perhaps more idiomatic and gives better compile time type checking with no run-time panics but it possibly "hides" the "first-class function" aspect of the task.

package main

import "fmt"

func main() {
	var (
		x  Float   = 2
		xi Float   = .5
		y  Float   = 4
		yi Float   = .25
		z  FloatFn = func() float64 { return float64(x + y) }
		zi FloatFn = func() float64 { return 1 / float64(x+y) }
	// point A

	numbers := []Number{&x, &y, z}
	inverses := []Number{&xi, &yi, zi}
	// point B

	mfs := make([]FloatFnArg, len(numbers))
	for i := range mfs {
		mfs[i] = multiplier(numbers[i], inverses[i])
	// pointC

	for _, mf := range mfs {

func multiplier(n1, n2 Number) FloatFnArg {
	return func(m float64) float64 {
		// close on interface objects n1, n2, and m
		return n1.Value() * n2.Value() * m

type Float float64
type FloatFn func() float64
type FloatFnArg func(float64) float64

func (f Float) Value() float64    { return float64(f) }
func (fn FloatFn) Value() float64 { return fn() }

type Number interface {
	Value() float64