boost.lambda

<pre name="code" class="cpp">// boost.lambda表达式用法// made by davidsu33// 2014-9-22#include "stdafx.h"#include <boost/typeof/typeof.hpp>#include <boost/lambda/lambda.hpp>#include <boost/bind/bind.hpp>#include <boost/assign.hpp>#include <boost/core/enable_if.hpp>#include <boost/operators.hpp>#include <vector>#include <utility>#include <memory>#include <algorithm>#include <cassert>#include <iostream>using namespace std;//Boost的简单用法void lambda_easy_use(){using namespace boost::assign;vector<int> arr = list_of(0).repeat(19, 0);int begin = 0;for_each(arr.begin(), arr.end(),(boost::lambda::_1 = boost::lambda::var(begin)++, boost::lambda::_1 += 10,boost::lambda::_1 -= 5));for (unsigned i=0; i<arr.size(); ++i){assert(arr[i] == 5+i);}cout<<"lambda_easy_use passed"<<endl;}//Boost的仿函数调用void lambda_functors(){int i=10, j=20;int r = (boost::lambda::_1 + boost::lambda::_2)(i,j);assert(r == (i+j));BOOST_AUTO(br, (boost::lambda::_1 - boost::lambda::_2)(i, j));assert(br == (i-j));//多次运算BOOST_AUTO(br2, (boost::lambda::_1 - boost::lambda::_2, boost::lambda::_1 += boost::lambda::constant(10))(i, j));//??br2 == 20，br2的取值由第二个表达式赋予assert(br2 == i);assert(i == 20);}template<class T>T fun(const T& value){//要求输入值必须为整型typedef boost::enable_if<boost::is_integral<T>, T>::type TType;cout<<"fun is called!"<<endl;cout<<"the value:"<<value<<endl;return value+100;}//通过boost operator实现>操作符struct SortedData :boost::less_than_comparable1<SortedData>{SortedData():x(0),y(0){};SortedData(double sx, double sy):x(sx),y(sy){};bool operator<(const SortedData& other) const{return dist() < other.dist();}double dist() const{return sqrt(x*x + y*y);}void fillRandamData(){x = rand() %1000;y = rand() % 500;}friend ostream& operator<<(ostream & ostr, const SortedData& s){ostr << "x=" << s.x <<" y="<<s.y<<endl;return ostr;}//x distdouble x;//y distdouble y;};void lambda_call(){vector<int> v;using namespace boost::assign;v += 1,2,4,8,16;for_each(v.begin(), v.end(), fun<int>);//准备排序数据SortedData s1(10, 20), s2(1,2);assert(s1 > s2);//boost::lambda::placehoder1_type 等价于boost::lambda::_1//详见boost::lambda::core.hpp文件vector<SortedData> vs2(10);std::for_each(vs2.begin(), vs2.end(), boost::bind(&SortedData::fillRandamData, boost::lambda::placeholder1_type()));std::copy(vs2.begin(), vs2.end(), ostream_iterator<SortedData>(cout, "\n"));//进行排序cout<<"排序结果"<<endl;std::sort(vs2.begin(), vs2.end(), boost::lambda::_1 < boost::lambda::_2);std::copy(vs2.begin(), vs2.end(), ostream_iterator<SortedData>(cout, "\n"));}void lambda_access_member(){vector<SortedData> vs2(10);std::for_each(vs2.begin(), vs2.end(), boost::bind(&SortedData::fillRandamData, boost::lambda::placeholder1_type()));std::copy(vs2.begin(), vs2.end(), ostream_iterator<SortedData>(cout, "\n"));//进行排序cout<<"排序结果"<<endl;std::sort(vs2.begin(), vs2.end(), boost::lambda::_1 < boost::lambda::_2);std::copy(vs2.begin(), vs2.end(), ostream_iterator<SortedData>(cout, "\n"));SortedData s;boost::bind<double&>(&SortedData::x, boost::lambda::_1)(s) = 100;assert(s.x == 100);double m=0;//std::for_each(vs2.begin(), vs2.end(), boost::bind<double>(&SortedData::x, boost::lambda::_1) );//std::for_each(vs2.begin(), vs2.end(), boost::bind(boost::type<double>(),&SortedData::y, boost::lambda::_1) = 200);}int _tmain(int argc, _TCHAR* argv[]){lambda_easy_use();lambda_functors();lambda_call();lambda_access_member();getchar();return 0;}