对于 c++ 中的每个并将值分配给 std::vector

Question

如何为std::vector使用“for each”指令的元素赋值？我试图做这样的事情：

std::vector<int> A(5);
for each(auto& a in A)
    a = 4;

但后来我收到以下错误：

error C3892 : 'a' : you cannot assign to a variable that is const

Answer 1

for_each 算法似乎不适合这种类型的问题。如果我误解了这个问题，请告诉我。

    // You can set each value to the same during construction
    std::vector<int> A(10, 4);  // 10 elements all equal to 4

    // post construction, you can use std::fill
    std::fill(A.begin(), A.end(), 4);

    // or if you need different values via a predicate function or functor
    std::generate(A.begin(), A.end(), predicate);

    // if you really want to loop, you can do that too if your compiler 
    // supports it VS2010 does not yet support this way but the above 
    // options have been part of the STL for many years.

    for (int &i : A) i = 4;

就我个人而言，我还没有找到 for_each 算法的好用处。它一定对某些东西有好处，因为它被放入了库中，但我在 10 多年的 C++ 编程中从未需要它。在我看来，那个不是特别有用。