本文介绍了如何从C ++ 11匿名函数内部访问局部变量?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在对向量(权重)进行简单的归一化，试图利用STL算法使代码尽可能清晰(我意识到这对于for循环来说是微不足道的):
I'm doing a simple normalization on a vector (weights), trying to make use of STL algorithms to make the code as clean as possible (I realize this is pretty trivial with for loops):
float tot = std::accumulate(weights.begin(), weights.end(), 0.0);
std::transform(weights.begin(), weights.end(), [](float x)->float{return(x/tot);});
目前，匿名函数不可见tot，因此无法编译.使局部变量对匿名函数可见的最佳方法是什么?
At present, tot is not visible to the anonymous function, so this doesn't compile. What's the best way of making a local variable visible to the anonymous function?
推荐答案
您需要关闭.
float tot = std::accumulate(weights.begin(), weights.end(), 0);
std::transform(weights.begin(), weights.end(), [tot](float x)->float{return(x/tot);});
在这种情况下，tot被值捕获. C ++ 11 lambdas支持通过以下方式捕获:
In this case tot is captured by value. C++11 lambdas support capturing by:
- 值
[x] - 参考
[&x] - 通过引用
[&]当前在范围内的任何变量 - 与3相同，但按值
[=]
- value
[x] - reference
[&x] - any variable currently in scope by reference
[&] - same as 3, but by value
[=]
您可以在逗号分隔的列表[x, &y]中混合以上任何内容.
You can mix any of the above in a comma separated list [x, &y].
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