Implement recursive closures in Go

Introduction

Studying Go language version 2 means that I tried to study algorithms with Go.

Recursive closure

First of all, what is a closure, I will describe the sentence that I referred to below.

Go's anonymous function is a "closure". Closures are called "function closures" in Japanese, and are "confined (closures)" as a set of functions and "outside function" environments related to function processing.

So it represents an anonymous function. This time I started by using this to create a recursive function.

1. I created a function [func fact (n int) int] that calculates the factorial below.

fact.go

package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	r := bufio.NewReader(os.Stdin)
	w := bufio.NewWriter(os.Stdout)
	defer w.Flush()

	var a int

	fmt.Fscan(r, &a)

	result := solveFact(a)
	fmt.Print(result)
}

func solveFact(x int) int {
	var fact func(n int) int
	 fact = func(n int) int{
		if n == 0{ return 1 }
		return n * fact(n - 1)
	}
	return fact(x)
}

Execution result

❯ go run fact.go
4
24

2. I created a function [func fib (n int) int] that calculates the Fibonacci sequence.

fib.go

package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	r := bufio.NewReader(os.Stdin)
	w := bufio.NewWriter(os.Stdout)
	defer w.Flush()

	var a int

	fmt.Fscan(r, &a)

	result := solveFib(a)
	fmt.Print(result)
}

func solveFib(x int) int {
	var fib func(n int) int
	fib = func(n int) int{
		if n <= 1{return n}
		return fib(n -1) + fib(n - 2)
	}
	return fib(x)
}

Execution result

❯ go run fib.go
10
55

Summary

Fmt.Scan () / fmt.Printf () is used for input and output. However, I am afraid of the amount of input and output, so I use bufio and try to buffer it.