Go中的短路评估 [英] Short circuit evaluation in Go

问题描述

我对短路评估的理解是，仅在if语句中需要时才调用表达式.Go会遵循吗?

My understanding of short circuit evaluation is that an expression is only called when needed in an if statement. Does Go follow this?

例如，我平均可以从以下方面获得更好的性能:

For instance, would I get better performance on average from:

if !isValidQueryParams(&queries) || r == nil || len(queries) == 0 {
    return "", fmt.Errorf("invalid querystring")
}

...对此:

if r == nil || len(queries) == 0 || !isValidQueryParams(&queries) {
    return "", fmt.Errorf("invalid querystring")
}

...因为 isValidQueryParams 是一个比 r == nil 或测试地图长度要大得多的开销的函数?

...since isValidQueryParams is a function with much more overhead than r == nil or testing the length of a map?

即解释器将首先评估r == nil，看到它是正确的，而不用费心评估其他条件吗?

i.e. will the interpreter evaluate r == nil first, see it's true and not bother to evaluate the other conditions?

错误地将短路评估称为惰性评估

Incorrectly referred to short circuit evaluation as lazy evaluation

推荐答案

感谢Kostix和mkrieger的回答-他们是正确的，我指的是短路评估，而不是惰性评估.

Thank you to Kostix and mkrieger for their answers - they are correct, I'm referring to short circuit evaluation and not lazy evaluation.

Go确实实现了正常的短路评估，可以通过以下代码推导出来

Go does implement normal short circuit evaluation, as can be deduced with the following code:

package main

import "fmt"

func main() {
    for i := 0; i < 10; i++ {
        if testFunc(1) || testFunc(2) {
            // do nothing
        }
    }
}

func testFunc(i int) bool {
    fmt.Printf("function %d called\n", i)
    return true
}

...它将始终显示:

...which will always give:

$ function 1 called
$ function 1 called
$ function 1 called
$ function 1 called
$ function 1 called
$ function 1 called
$ function 1 called
$ function 1 called
$ function 1 called
$ function 1 called

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