英文:
a comparison equals to true, but when i put it as if condition, why it is not evaluated as true?
问题
以下是翻译好的内容：
a := "ALL"
b := "not all"
if (a == "ALL") != (b == "ALL") {
fmt.Printf("为什么没有进入这个条件分支？\n")
}
这是我写的一段 Go 代码，如果 a 和 b 中只有一个等于 "ALL"，则打印一些内容。但为什么 fmt.Printf 没有触发呢？
然而，下面的代码确实会打印：
c := (a == "ALL") != (b == "ALL")
if c {
fmt.Printf("如果将结果赋值给 c，就会进入这里\n")
}
但是这两段代码有什么区别呢？
我还在 Go Playground 上粘贴了上述代码：http://play.golang.org/p/e5tNai_d20。非常感谢任何人能解释一下！提前感谢！
英文:
a := "ALL"
b := "not all"
if (a == "ALL") != (b == "ALL") {
fmt.Printf("why not falling into this case?\n")
}
Here is a piece of Go code I wrote, to print something if a and b have exactly one to be "ALL". But why the fmt.Printf is not triggered?
However the following does print:
c := (a == "ALL") != (b == "ALL")
if c {
fmt.Printf("if assign to c, do fall in here\n")
}
But what's the difference between the two pieces?
I also pasted the above code in the go playground: http://play.golang.org/p/e5tNai_d20 Anyone's explanation will be greatly appreciated! Thanks in advance.
答案1
得分: 7
这是一个Go 1.5的bug，与这个问题相似：https://github.com/golang/go/issues/12226
该问题已在主分支上修复，所以你可以降级到1.4.2并等待下一个版本发布，或者编译主分支的最新代码。
编辑：Go 1.5.1已发布，其中包含了修复此问题的补丁。
英文:
It is a go 1.5 bug, and looks similiar to this one : https://github.com/golang/go/issues/12226
It is fixed on the master branch, so you can either downgrade to 1.4.2 and wait for the next release, or compile the tip of master.
Edit : Go1.5.1 has been released and it contains the fix to this issue
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