C++之not1和not2

not1是构造一个与谓词结果相反的一元函数对象，not2是构造一个与谓词结果相反的二元函数对象。

not1：

 1 // not1 example
 2 #include <iostream>     // std::cout
 3 #include <functional>   // std::not1
 4 #include <algorithm>    // std::count_if
 5 
 6 struct IsOdd {
 7   bool operator() (const int& x) const {return x%2==1;}
 8   typedef int argument_type;
 9 };
10 
11 int main () {
12   int values[] = {1,2,3,4,5};
13   int cx = std::count_if (values, values+5, std::not1(IsOdd()));
14   std::cout << "There are " << cx << " elements with even values.\n";
15   return 0;
16 }

 

not2：

 1 // not2 example
 2 #include <iostream>     // std::cout
 3 #include <functional>   // std::not2, std::equal_to
 4 #include <algorithm>    // std::mismatch
 5 #include <utility>      // std::pair
 6 
 7 int main () {
 8   int foo[] = {10,20,30,40,50};
 9   int bar[] = {0,15,30,45,60};
10   std::pair<int*,int*> firstmatch,firstmismatch;
11   firstmismatch = std::mismatch (foo, foo+5, bar, std::equal_to<int>());
12   firstmatch = std::mismatch (foo, foo+5, bar, std::not2(std::equal_to<int>()));
13   std::cout << "First mismatch in bar is " << *firstmismatch.second << '\n';
14   std::cout << "First match in bar is " << *firstmatch.second << '\n';
15   return 0;
16 }

 

posted @ 2020-12-03 11:16  Mr-xxx  阅读(1043)  评论(0)  编辑  收藏  举报