main.go 源码
// Copyright © 2018 Inanc Gumus
// Learn Go Programming Course
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
//
// For more tutorials : https://learngoprogramming.com
// In-person training : https://www.linkedin.com/in/inancgumus/
// Follow me on twitter: https://twitter.com/inancgumus
package main
import (
"fmt"
"os"
"strconv"
)
func main() {
// n and err belongs to the main function now
// not only to the if statement below
var (
n int
err error
)
if a := os.Args; len(a) != 2 {
fmt.Println("Give me a number.")
} else if n, err = strconv.Atoi(a[1]); err != nil {
// here else if uses the main func's n and err
// variables instead of its own
fmt.Printf("Cannot convert %q.\n", a[1])
} else {
// assigns the result back into main func's
// n variable
n *= 2
fmt.Printf("%s * 2 is %d\n", a[1], n)
}
// if statement has calculated the result using
// the main func's n variable
//
// so, that's why it prints the correct result here
fmt.Println("n is", n)
}
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