英文:
variable declared and not used in a for loop
问题
这个问题在这里已经出现了几次，但我认为我的经验是独特的。以下是我的代码。
type Stack []Weight
func newStack( size int, startSpread Spread ) Stack {
stack := make(Stack, size)
for _, curWeight := range stack {
curWeight = Weight{ startSpread, rand.Float64( ), rand.Float64( ) }
}
return stack
}
为什么gc告诉我我没有使用curWeight？
英文:
This one has come up a couple times for Go here, but I think my experience is unique. Here are my codes.
type Stack []Weight
func newStack( size int, startSpread Spread ) Stack {
stack := make(Stack, size)
for _, curWeight := range stack {
curWeight = Weight{ startSpread, rand.Float64( ), rand.Float64( ) }
}
return stack
}
Why is gc telling me I'm not using curWeight?
答案1
得分: 5
请注意，range构造（for _, curWeight := range stack）会逐个复制元素。所以，你只是复制了一个值，然后没有将复制用于任何进一步的计算、打印或返回。你只是再次丢弃了复制品。
所以我猜你最初的想法是将权重添加到堆栈并返回它。让我们这样做：
func newStack(size int, startSpread Spread) Stack {
stack := make(Stack, size)
for i := 0; i < size; i++ {
stack[i] = Weight{startSpread, rand.Float64(), rand.Float64()}
}
return stack
}
英文:
Please note that the range construct (for _, curWeight := range stack) does copy the elements, one after another. So, you are just copying a value, and then you do not use the copy for any further computations, printing or returning. You just drop the copy again.
So I guess your initial idea was to add the weight to the stack and return it. Let`s do that:
func newStack(size int, startSpread Spread) Stack {
stack := make(Stack, size)
for i := 0; i < size; i++ {
stack[i] = Weight{startSpread, rand.Float64(), rand.Float64()}
}
return stack
}
答案2
得分: 1
你在两个地方都给curWeight赋值了，但是你在任何一个地方都没有使用这个值。
Go语言要求如果你给一个变量赋值，那么你必须在程序的某个潜在点读取这个值。如果你不打算读取它，那么可以赋值给_。
英文:
You're assigning to curWeight twice, but you're not using the value in either place.
Go insists that if you assign a value to a variable, then you have to read that value back at some potential point in your program. If you're not going to read it, then assign to _ instead.
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