更新时间:2023-11-27 08:32:22
派对迟到了.但是:我会遍历索引.但不是使用经典的 for
循环,而是使用基于范围的 for
循环在索引上:
Rather late to the party. But: I would iterate over indices. But not with the classical for
loop but instead with a range-based for
loop over the indices:
for(unsigned i : indices(containerA)) {
containerA[i] = containerB[i];
}
indices
是一个简单的包装函数,它返回索引的(惰性求值)范围.由于实现(虽然简单)有点太长,无法在此处发布,您可以在 GitHub 上找到实现.
indices
is a simple wrapper function which returns a (lazily evaluated) range for the indices. Since the implementation – though simple – is a bit too long to post it here, you can find an implementation on GitHub.
此代码与使用手动的经典 for
循环一样高效.
This code is as efficient as using a manual, classical for
loop.
如果这种模式经常出现在您的数据中,请考虑使用另一种模式,该模式 zip
生成两个序列并生成一系列元组,对应于成对的元素:
If this pattern occurs often in your data, consider using another pattern which zip
s two sequences and produces a range of tuples, corresponding to the paired elements:
for (auto& [a, b] : zip(containerA, containerB)) {
a = b;
}
zip
的实现留给读者作为练习,但它很容易从 indices
的实现中得到.
The implementation of zip
is left as an exercise for the reader, but it follows easily from the implementation of indices
.
(在 C++17 之前,您必须改为编写以下代码:)
(Before C++17 you’d have to write the following instead:)
for (auto items&& : zip(containerA, containerB))
get<0>(items) = get<1>(items);