关于lambda的基础知识，请参考上一篇的地址如下：
http://www.cnblogs.com/davidgu/p/4825625.html
我们再举个STL使用Lambda来进行排序的例子，如下：
Person.h
#ifndef _Domain_Models_Person_H_
#define _Domain_Models_Person_H_ #include <iostream>
#include <string>
#include <deque> using namespace std; class Person
{
friend ostream& operator<< (ostream& s, const Person& p);
private:
string fn; // first name
string ln; // last name
int age;
public:
Person() { }
Person(const string& f, const string& n)
: fn(f), ln(n)
{
}
string firstname() const;
string lastname() const;
int getAge() const;
void setAge(int a);
static bool sortByName(const Person& p1, const Person& p2);
static bool sortByAge(const Person& p1, const Person& p2);
static void sortDequeByName(deque<Person> &persons);
static void sortDequeByAge(deque<Person> &persons);
static void printPersonDeques(deque<Person> persons);
}; #endif
Person.cpp
#include <algorithm>
#include "Person.h" inline string Person::firstname() const
{
return fn;
} inline string Person::lastname() const
{
return ln;
} inline int Person::getAge() const
{
return age;
} void Person::setAge(int a)
{
age = a;
} /* binary function predicate:
* - returns whether a person is less than another person
*/
bool Person::sortByName(const Person& p1, const Person& p2)
{
/* a person is less than another person
* - if the last name is less
* - if the last name is equal and the first name is less
*/
return p1.lastname()<p2.lastname() ||
(p1.lastname() == p2.lastname() &&
p1.firstname()<p2.firstname());
} // another binary predicate
bool Person::sortByAge(const Person& p1, const Person& p2)
{
return p1.getAge() < p2.getAge();
} void Person::sortDequeByName(deque<Person> &persons)
{
// sort elements
sort(persons.begin(), persons.end(), // range
Person::sortByName); // sort criterion
} void Person::sortDequeByAge(deque<Person> &persons)
{
// sort elements
sort(persons.begin(), persons.end(), // range
Person::sortByAge); // sort criterion
} ostream& operator<< (ostream& s, const Person& p)
{
s << "[" << p.lastname() << ", " << p.firstname() << ", " << p.getAge() << "]";
return s;
} void Person::printPersonDeques(deque<Person> persons)
{
deque<Person>::iterator pos;
for (pos = persons.begin(); pos != persons.end(); ++pos)
{
cout << *pos << endl;
}
}
LambdaTest.cpp
#include <algorithm>
#include <deque>
#include <iostream>
#include "LambdaTest.h"
#include "../../Core/ContainerUtil.h" using namespace std; void LambdaTest::sortByLambda()
{
// create some persons
Person p1("nicolai", "josuttis");
Person p2("ulli", "josuttis");
Person p3("anica", "josuttis");
Person p4("lucas", "josuttis");
Person p5("lucas", "otto");
Person p6("lucas", "arm");
Person p7("anica", "holle");
p1.setAge();
p2.setAge();
p3.setAge();
p4.setAge();
p5.setAge();
p6.setAge();
p7.setAge(); // insert person into collection coll
deque<Person> coll;
coll.push_back(p1);
coll.push_back(p2);
coll.push_back(p3);
coll.push_back(p4);
coll.push_back(p5);
coll.push_back(p6);
coll.push_back(p7); cout << "persons before sort:" << endl;
Person::printPersonDeques(coll); // sort Persons according to lastname (and firstname)
sort(coll.begin(), coll.end(), // range
[](const Person& p1, const Person& p2) { // sort criterion
return p1.lastname()<p2.lastname() ||
(p1.lastname() == p2.lastname() &&
p1.firstname()<p2.firstname());
}); cout << "persons after sort by name:" << endl;
Person::printPersonDeques(coll); // sort Persons according to age
sort(coll.begin(), coll.end(), // range
[](const Person& p1, const Person& p2) { // sort criterion
return p1.getAge() < p2.getAge();
}); cout << "persons after sort by age:" << endl;
Person::printPersonDeques(coll);
} void LambdaTest::run()
{
printStart("sortByLambda()");
sortByLambda();
printEnd("sortByLambda()");
}
运行结果:
---------------- sortByLambda(): Run Start ----------------
persons before sort:
[josuttis, nicolai, 20]
[josuttis, ulli, 30]
[josuttis, anica, 18]
[josuttis, lucas, 2]
[otto, lucas, 22]
[arm, lucas, 35]
[holle, anica, 95]
persons after sort by name:
[arm, lucas, 35]
[holle, anica, 95]
[josuttis, anica, 18]
[josuttis, lucas, 2]
[josuttis, nicolai, 20]
[josuttis, ulli, 30]
[otto, lucas, 22]
persons after sort by age:
[josuttis, lucas, 2]
[josuttis, anica, 18]
[josuttis, nicolai, 20]
[otto, lucas, 22]
[josuttis, ulli, 30]
[arm, lucas, 35]
[holle, anica, 95]
---------------- sortByLambda(): Run End ----------------