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() {
// UNCOMMENT THIS TO SEE IT IN ACTION:
// var n int
if a := os.Args; len(a) != 2 {
fmt.Println("Give me a number.")
} else if n, err := strconv.Atoi(a[1]); err != nil {
// else if here shadows the main func's n
// variable and it declares it own
// with the same name: n
fmt.Printf("Cannot convert %q.\n", a[1])
} else {
fmt.Printf("%s * 2 is %d\n", a[1], n*2)
}
// n here belongs to the main func
// not to the if statement above
// UNCOMMENT ALSO LINES BELOW TO SEE IT IN ACTION:
// fmt.Printf("n is %d. 👻 👻 👻 - you've been shadowed ;-)\n", n)
}
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