4. auto __end = end_expr(__range); 5. for (;__begin != __end; ++__begin) { 6. range_declaration = *__begin; 7. loop_statement 8. } 9. } 1. 2. 3. 4. 5. 6. 7. 8. 9. 请注意,“等价于”并不表示编译器就是这么实现range-based for loops的。只是说两者的运行效果等价 ...
for(autowhatever =begin(a); whatever !=end(a); ++whatever) {autox = *whatever;/* ... */} 对于一般的重载了begin和end方法的对象(比如std::vector), 这两个全局函数会调用它们的这两个方法, 对于C风格数组, std::begin 和 std::end 是模板特化的, 简单来说就是特判了【特化为数组的引用】, ...
range-for是C++ 11新增特性,用于循环迭代一个“范围”,该“范围”类似于包含有begin()和end()方法的STL序列容器。所有的STL标准容器都适用于该“范围”,例如vector、string等等。数组也同样可以,只要定义了begin()和end()方法的任何“范围”都可以使用for来循环迭代容器里面的元素,如istream。 语法: for(range_de...
With arrays taken care of by the first rule, the second rule makes sure that all the standard containers as well as all the user-defined ones that follow the standard sequence interface will work with range-basedforout of the box. For example, in ODB (an ORM for C++), we have the co...
When used with a (non-const) object that has copy-on-write semantics, the range-basedforloop may trigger a deep copy by (implicitly) calling the non-constbegin()member function. If that is undesirable (for instance because the loop is not actually modifying the object), it can be avoided...
在C++98标准中,基于范围的for循环(range-based for loop)是不被支持的。这种循环结构是C++11及以后版本中引入的,用于简化对容器(如std::vector、std::list等)或数组的遍历。基于范围的for循环自动处理容器的开始和结束迭代器,使得代码更加简洁易读。 替代方案以在C++98中实现类似功能 在C++98中,你可以使用传统的...
直觉上c的类型应该是const char&,但是怎么推理得到c的类型呢?细究起来确实花了一番功夫。 使用auto声明的变量必须要给初始值,而这里的语法没有给初始值。Range-Based for loop应该是一种语法糖,实际上编译器应该是当成普通的for循环来处理的。 从cppreference(https://en.cppreference.com/w/cpp/language/range...
Range-based for loop Range-based for loop 在范围上执行for循环。 用作更易读的,相当于传统的用于循环操作范围内的值,例如容器中的所有元素。 句法 attr(optional) for ( range_declaration : range_expression ) loop_statement attr - any number of attributes range_declaration - a declaration ...
The range-based for loop follows this general format:for( declaration : expression) { //do some loop stuff } C++ CopyHere’s an simple example which prints all the elements in a std::vector:std::vector<int> v1 = {-1, 3, 5, -8, 0}; std::cout << std::endl << "v1: " <...
Range-based for loops won’t work with decayed C-style arrays. This is because a range-based for-loop needs to know the length of the array to know when traversal is complete, and decayed C-style arrays do not contain this information. Range-based for loops also won’t work with enumer...