20:最好用pass-by-reference-to-const替换pass-by-value 1.引用传值,本质上也是传递一个指针,如果是传递内置类型,就不如采用直接传值了。(另外STL的迭代器和函数对象也是) 2.用引用传值通常比较高效,并可避免切割问题。 3.切割问题:当使用传值方式时,一个子类对象被传递,被当一个父类对象接收时,此时只能调...
voiddisplay(constvector<int>*vec){if(!vec){}for(intix=0;ix<vec->size();++ix)//指针取函数的用法是vec->size()cout<<(*vec)[ix]<<' ';//指针用索引的方式,先(*vec)得到目标。}intmain(){intia[8]={8,32,3,13,1,...};vector<int>vec(ia,ia+8);display(&vec);//传址} 动态内...
If you just need to look at the argument: Pass by const reference. If you need to make a copy anyways, pass by value and work on the argument. The rationale for this rule is simple: Big copies are very expensive, so you should avoid them. But if you need to make one anyways,...
; // error: cannot modify through reference to const std::cout << r2 << '\n'; // prints s, which now holds "Example" }They can also be used to implement pass-by-reference semantics in function calls: Run this code #include <iostream> #include <string> void double_string(std::...
std::function<UniformValue(constJsonishValue *)> parse_func_; }; 这样写法没有问题,但是 clang 编译器提示 "Clang-Tidy: Pass by value and use std::move" 这里很有意思了, 为什么我所认为的使用 const reference 的写法明明是高效传递变量,避免不必要的 copy 操作,为何让我改用低效的 ...
举个例子, 传递参数使用pass-by-value还是pass-by-reference, C内置类型往往使用值传递, 包括指针; 而迭代器和函数对象基于C指针所以也使用值传递, 但是Object-Oriented C++中的自定义对象使用pass-by-reference-to-const, 从而避免频繁的调用构造函数和析构函数. ...
Executors also decouple those concepts away from application code, by providing a unified API for creating and scheduling tasks.Tasks communicate with each other using result objects. A result object is an asynchronous pipe that pass the asynchronous result of one task to another ongoing-task. ...
inline void Prefetch_Block(const void* addr, size_t sz, int hint) { char* pref_addr = (char*)addr; size_t pref_iters = (sz + CACHE_LINE_SIZE - 1) / CACHE_LINE_SIZE; for (int i = 0; i < pref_iters; i++) { _mm_prefetch(pref_addr, hint /*_MM_HINT_T1*/); ...
classIExample{android::binder::StatusReadStrings(constandroid::String16&in_neverNull,conststd::unique_ptr<android::String16>&in_maybeNull);}; Note that by default, the generated C++ passes a const reference to the value of a parameter and rejects null references with a NullPointerException sent...
8.2.7 When to Use Reference Arguments There are two main reasons for using reference arguments: 1) To allow you to alter a data object in the calling function 2) To speed up the program by passing a reference instead of an entire data object ...