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() {
if a := os.Args; len(a) != 2 {
// only a is available here
fmt.Println("Give me a number.")
// no need to return on error
// return
} else if n, err := strconv.Atoi(a[1]); err != nil {
// a, n and err are available here
fmt.Printf("Cannot convert %q.\n", a[1])
// no need to return on error
// return
} else {
// all of the variables (names)
// are available here
fmt.Printf("%s * 2 is %d\n", a[1], n*2)
}
// a, n and err are not available here
// they belong to the if statement
// TRY:
// fmt.Println(a, n, err)
}
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