go - 如何在 Go 中的 if 语句中更新变量的值？

Question

我正在尝试学习围棋，我创建了一个函数，我在其中声明了一个变量 game_ratio 并将其设置为 0.0。然后我有一个 if 语句，我在其中尝试更新 game_ratio 的值。当我尝试编译时，收到以下错误消息:'game_ratio 已声明但未使用'

这是我的功能:

func gameRatio(score1 int, score2 int, max_score float64) float64 {
    var game_ratio float64 = 0.0
    var scaled_score_1 = scaleScore(score1, max_score)
    var scaled_score_2 = scaleScore(score2, max_score)
    fmt.Printf("Scaled score for %v is %v\n", score1, scaled_score_1)
    fmt.Printf("Scaled score for %v is %v\n", score2, scaled_score_2)
    if score1 > score2 {
        game_ratio := (scaled_score_1+1.0)/(scaled_score_1+scaled_score_2+2.0) + 1.0*0.5
    }
    return game_ratio
}

下面是调用它的代码:

func main() {
    flag.Parse()
    s1 := flag.Arg(0)
    s2 := flag.Arg(1)
    i1, err := strconv.Atoi(s1)
    i2, err := strconv.Atoi(s2)
    if err != nil {
        fmt.Println(err)
        os.Exit(2)
    }
    fmt.Println("Game ratio is", gameRatio(i1, i2, 6))
}

ScaleScore 是我编写的另一个函数。如果我删除 if 语句，代码就可以工作。

要运行我的应用，我输入“rankings 28 24”

Answer 1

简短的变量声明是重新声明game_ratio。

game_ratio := (scaled_score_1+1.0)/(scaled_score_1+scaled_score_2+2.0) + 1.0*0.5

使用赋值。写:

game_ratio = (scaled_score_1+1.0)/(scaled_score_1+scaled_score_2+2.0) + 1.0*0.5

The Go Programming Language Specification

Short variable declarations

A short variable declaration uses the syntax:

ShortVarDecl = IdentifierList ":=" ExpressionList .

It is shorthand for a regular variable declaration with initializer expressions but no types:

"var" IdentifierList = ExpressionList .

Unlike regular variable declarations, a short variable declaration may redeclare variables provided they were originally declared earlier in the same block with the same type, and at least one of the non-blank variables is new. As a consequence, redeclaration can only appear in a multi-variable short declaration. Redeclaration does not introduce a new variable; it just assigns a new value to the original.