Golang golang-pi2go (snippet)

Go programming example 'golang-pi2go'

golang-pi2go

Golang beginners example: golang-pi2go

package main

import (
    "fmt"
    "math"
    "os"
    "os/signal"
    "simonwaldherr.de/go/golibs/xmath"
    "syscall"
)

type typeOfCalculation int

const (
    NULL typeOfCalculation = iota
    plus
    minus
    times
    divided
)

func waitForCtrlC() chan os.Signal {
    var signalChannel chan os.Signal
    signalChannel = make(chan os.Signal, 1)
    signal.Notify(signalChannel, syscall.SIGINT, syscall.SIGTERM)
    return signalChannel
}

func multipleOfFour(i int) bool {
    if i%4 == 0 {
        return true
    }
    return false
}

func πByLeibniz(stop chan os.Signal) float64 {
    var calculate = true
    go func() {
        <-stop
        calculate = false
    }()

    var π float64 = 1
    var toc = minus
    var denominator float64 = 3

    for calculate {
        if toc == minus {
            π = π - (1 / denominator)
            denominator += 2
            toc = plus
        } else {
            π = π + (1 / denominator)
            denominator += 2
            toc = minus
        }
    }
    return π * 4
}

func πByEuler(stop chan os.Signal) float64 {
    var calculate = true
    go func() {
        <-stop
        calculate = false
    }()

    var π float64 = 0
    var denominator float64 = 1

    for calculate {
        π = π + 1/(denominator*denominator)
        denominator++
    }
    return math.Sqrt(π * 6)
}

func πByPrime(stop chan os.Signal) float64 {
    var calculate = true
    go func() {
        <-stop
        calculate = false
    }()

    var π float64 = 1
    var denominator int = 2
    var prime int

    for calculate {
        prime = xmath.Prime(denominator)
        if multipleOfFour(prime - 1) {
            π = π * (1 + 1/float64(prime))
        } else {
            π = π * (1 - 1/float64(prime))
        }
        denominator++
    }
    return 2 / π
}

func πByGolang() float64 {
    return math.Pi
}

func main() {
    var algo string = ""
    stopChan := waitForCtrlC()

    if len(os.Args) > 1 {
        algo = os.Args[1]
    }

    switch algo {
    default:
        fmt.Print(πByGolang())
    case "leibniz", "Leibniz":
        fmt.Print(πByLeibniz(stopChan))
    case "euler", "Euler":
        fmt.Print(πByEuler(stopChan))
    case "prime", "Prime":
        fmt.Print(πByPrime(stopChan))
    }

    fmt.Print("\n")
}

Useful links

• Learn Go: https://golangr.com
• Download Go: https://golang.org