[TOC] # 簡介 謂詞是指普通函數或重載的operator()返回值是bool類型的函數對象(仿函數)。 如果operator接受一個參數，那么叫做一元謂詞,如果接受兩個參數，那么叫做二元謂詞，謂詞可作為一個判斷式。 # 一元謂詞 ~~~ struct GreaterThanFive { bool operator() (int v) { return v > 5; } }; //一元謂詞 void test01() { vector<int> v; for (int i = 0; i < 10; ++i) { v.push_back(i); } vector<int>::iterator ret = find_if(v.begin(), v.end(), GreaterThanFive()); if (ret == v.end()) { cout << "沒有找到!" << endl; } else { cout << "找到: " << *ret << endl; } //找到: 6 } ~~~ # 二元謂詞 ~~~ struct MyCompare { bool operator() (int v1, int v2) { return v1 > v2; } }; void test02() { vector<int> v; srand((unsigned)time(NULL)); for (int i = 0; i < 10; ++i) { v.push_back(rand() % 100); } for (vector<int>::iterator it = v.begin(); it != v.end(); it++) { cout << *it << " "; } cout << endl; //排序算法 sort(v.begin(), v.end(), MyCompare()); for (vector<int>::iterator it = v.begin(); it != v.end(); it++) { cout << *it << " "; } cout << endl; } ~~~