// OK: return pointers to elements with the value xvector find_all(const vector&, int x); // Bad: place pointers to elements with value x in-outvoid find_all(const vector&, vector& out, int x);
Note（注意）
包含多个（单独看都可以低成本移动）元素的结构体合起来移动时可能会代价高昂。
不推荐返回常量值。这种过时的建议现在已经被淘汰；它不会带来好处，而且其接口含有移动语义。
const vector fct(); // bad: that "const" is more trouble than it is worth vector g(const vector& vx){ // ... fct() = vx; // prevented by the "const" // ... return fct(); // expensive copy: move semantics suppressed by the "const"}
If a type is expensive to move (e.g., array), consider allocating it on the free store and return a handle (e.g., unique_ptr), or passing it in a reference to non-const target object to fill (to be used as an out-parameter).
译者注：POD是Plain old data structure的简称，是C++语言的标准中定义的一类数据结构，可以简单地理解只包含单纯数据类型的结构体。
To reuse an object that carries capacity (e.g., std::string, std::vector) across multiple calls to the function in an inner loop: treat it as an in/out parameter and pass by reference.
struct Package { // exceptional case: expensive-to-move object char header[16]; char load[2024 - 16];}; Package fill(); // Bad: large return valuevoid fill(Package&); // OK int val(); // OKvoid val(int&); // Bad: Is val reading its argument
译者注：示例代码说明的是POD使用引用传递输出值，而小数据者应该直接使用返回值。
Enforcement（实施建议）
Flag reference to non-const parameters that are not read before being written to and are a type that could be cheaply returned; they should be "out" return values.
警告那些没有在写之前读（没有输入用途）而且可以低成本返回的参数，它们应该作为返回值输出。
Flag returning a const value. To fix: Remove const to return a non-const value instead.
