使用STL通用算法find_if()在list中搜索对象

这是find()的一个更强大的版本。这个例子演示了find_if()，它接收一个函数对象的参数作为参数， 并

使用它来做更复杂的评价对象是否和给出的查找条件相付。
假设我们的list中有一些按年代排列的包含了事件和日期的记录。我们希望找出发生在1997年的事件。

/*
|| How to find things in an STL list MkII
*/
#include <string>
#include <list>
#include <algorithm>

class EventIsIn1997 {
public:
bool operator () (string& EventRecord) {
// year field is at position 12 for 4 characters in EventRecord
return EventRecord.substr(12,4)=="1997";
}
};

int main (void) {
list<string> Events;

// string positions 0123456789012345678901234567890123456789012345
Events.push_back("07 January 1995 Draft plan of house prepared");
Events.push_back("07 February 1996 Detailed plan of house prepared");
Events.push_back("10 January 1997 Client agrees to job");
Events.push_back("15 January 1997 Builder starts work on bedroom");
Events.push_back("30 April 1997 Builder finishes work");

list<string>::iterator EventIterator = find_if (Events.begin(), Events.end(),

EventIsIn1997());

// find_if completes the first time EventIsIn1997()() returns true
// for any object. It returns an iterator to that object which we
// can dereference to get the object, or if EventIsIn1997()() never
// returned true, find_if returns end()
if (EventIterator==Events.end()) {
cout << "Event not found in list" << endl;
}
else {
cout << *EventIterator << endl;
}
}

这是程序的输出：

10 January 1997 Client agrees to job