Golang golang-defaultoptional (snippet)

Go programming example 'golang-defaultoptional'

golang-defaultoptional

Golang beginners example: golang-defaultoptional

package main

import (
    "bufio"
    "errors"
    "fmt"
    "os"
    "reflect"
    "simonwaldherr.de/go/golibs/as"
)

func defaultValue(va ...interface{}) (int64, int64, int64, int64) {
    var v [4]int64
    var typeof = ""
    for i := 0; i < 4; i++ {
        if i < len(va) {
            typeof = as.String(reflect.TypeOf(va[i]))
        } else {
            typeof = "nil"
        }

        if typeof == "int" || typeof == "int8" || typeof == "int16" || typeof == "int32" || typeof == "int64" {
            v[i] = as.Int(va[i])
        } else {
            switch i {
            case 0:
                v[i] = 2
            case 1:
                v[i] = 4
            case 2:
                v[i] = 8
            case 3:
                v[i] = 16
            }
        }
    }
    return v[0], v[1], v[2], v[3]
}

func askFor(question string) string {
    scanner := bufio.NewScanner(os.Stdin)
    fmt.Printf("# %v: ", question)
    scanner.Scan()
    return string(scanner.Text())
}

func askOnRuntime(va ...interface{}) (int64, int64, int64, int64) {
    var v [4]int64
    var typeof = ""
    for i := 0; i < 4; i++ {
        if i < len(va) {
            typeof = as.String(reflect.TypeOf(va[i]))
        } else {
            typeof = "nil"
        }

        if typeof == "int" || typeof == "int8" || typeof == "int16" || typeof == "int32" || typeof == "int64" {
            v[i] = as.Int(va[i])
        } else {
            switch i {
            case 0:
                v[i] = as.Int(askFor("first value"))
            case 1:
                v[i] = as.Int(askFor("second value"))
            case 2:
                v[i] = as.Int(askFor("third value"))
            case 3:
                v[i] = as.Int(askFor("fourth value"))
            }
        }
    }
    return v[0], v[1], v[2], v[3]
}

func optionalValue(v ...interface{}) (int64, error) {
    countArguments := len(v)
    if countArguments < 4 && countArguments > 0 { //we check for the right amount of arguments
        switch countArguments {
        case 1:
            return as.Int(v[0]), nil
        case 2:
            return as.Int(v[0]) * as.Int(v[1]), nil
        case 3:
            return as.Int(v[0]) * as.Int(v[1]) * as.Int(v[2]), nil
        }
    }
    return int64(len(v)), errors.New(fmt.Sprintf("wrong number of arguments, expected between 1 and 3, discovered %v", countArguments))
}

func printAll(v ...interface{}) {
    for _, x := range v {
        fmt.Printf("%v\t", x)
    }
    fmt.Println()
}

func sprintAll(v ...interface{}) string {
    var str = ""
    for _, x := range v {
        str += fmt.Sprintf("%v\t", x)
    }
    str += fmt.Sprintln()
    return str
}

func first(v ...interface{}) interface{} {
    return v[0]
}

func main() {
    fmt.Printf("first(optionalValue(12, 23, 42))\n%v\n", first(optionalValue(12, 23, 42)))
    fmt.Printf("\noptionalValue()\n%v", sprintAll(optionalValue()))
    fmt.Printf("\noptionalValue(23)\n%v", sprintAll(optionalValue(23)))
    fmt.Printf("\noptionalValue(23, 42)\n%v", sprintAll(optionalValue(23, 42)))
    fmt.Printf("\noptionalValue(12, 23, 42)\n%v", sprintAll(optionalValue(12, 23, 42)))
    fmt.Printf("\noptionalValue(1, 2, 3, 10)\n%v", sprintAll(optionalValue(1, 2, 3, 10)))
    fmt.Println("\ndefaultValue(3.1415, 4, 5)")
    printAll(defaultValue(3.1415, 4, 5))
    fmt.Println("\ndefaultValue(\"1\", 3, 5, 7, 9)")
    printAll(defaultValue("1", 3, 5, 7, 9))
    fmt.Println("\ndefaultValue(\"1\", false, nil, 7, 9)")
    printAll(askOnRuntime("1", false, nil, 7, 9))
}

Useful links

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