正文
C++ 11 - STL - 函数对象(Function Object) (中)
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我们再来看一个复杂的例子
需求：
我们需要对集合内每个元素加上一个特定的值
代码如下：
AddInt.h
class AddInt
{
private:
int theValue; // the value to add
public:
// constructor initializes the value to add
AddInt(int v) : theValue(v) { } // the "function call" for the element adds the value
void operator() (int& elem) const
{
elem += theValue;
}
};
设置一个打印模板类
print.hpp
template <typename T>
inline void PRINT_ELEMENTS (const T& coll,
const std::string& optstr="")
{
std::cout << optstr;
for (const auto& elem : coll) {
std::cout << elem << ' ';
}
std::cout << std::endl;
}
测试程序:
list<int> coll;// insert elements from 1 to 9
for (int i = ; i <= ; ++i) {
coll.push_back(i);
}PRINT_ELEMENTS(coll, "initialized: ");// add value 10 to each element
for_each(coll.begin(), coll.end(), // range
AddInt()); // operationPRINT_ELEMENTS(coll, "after adding 10: ");// add value of first element to each element
for_each(coll.begin(), coll.end(), // range
AddInt(*coll.begin())); // operationPRINT_ELEMENTS(coll, "after adding first element: ");
运行结果:
---------------- addFuncObject(): Run Start ----------------
initialized: 1 2 3 4 5 6 7 8 9
after adding 10: 11 12 13 14 15 16 17 18 19
after adding first element: 22 23 24 25 26 27 28 29 30
---------------- addFuncObject(): Run End ----------------
