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Boost教程（六）其他杂项
|C++Boost|
Word count: 597|Reading time: 3 min

类型转换lexical_cast

最近发现除了Qt外，用boost做一些类型转换也很好，这样可以避开QString这样的Qt数据类型了，需要使用的时模板函数lexical_cast，需要try catch

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try
{
	string s = "123";
    int num = boost::lexical_cast<int>(s);
}
catch (boost::bad_lexical_cast&  e)
{
    cout<<e.what()<<endl;
}

BOOST_FOREACH

只需要头文件#include <boost/foreach.hpp>

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vector<int> ages;
ages.reserve(20);
ages.push_back(2);  
ages.push_back(9);  
ages.push_back(14);  
ages.push_back(27);  
ages.push_back(39);  
BOOST_FOREACH(int age, ages)
{
    cout<< age <<endl;
}

实际使用中，最好定义一个宏：#define Foreach BOOST_FOREACH，宏最好不要是foreach，容易跟其他库（例如Qt）冲突

geometry

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#include <ros/ros.h>
#include <boost/assign.hpp>
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/linestring.hpp>
#include <boost/geometry/geometries/box.hpp>
#include <boost/geometry/geometries/ring.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/algorithms/transform.hpp>
#include <list>
using namespace std;
namespace bg = boost::geometry;
namespace bgi = bg::index;

using Point = bg::model::point<double, 2, bg::cs::cartesian>;
using Box = bg::model::box<Point>;
using Line = bg::model::linestring<Point>;
// 线段
using Segment = bg::model::segment<Point>;


int main(int argc, char** argv)
{
    ros::init(argc, argv, "test_boost");
    ros::NodeHandle nh;
    Point pt0(100, 100);
    Point pt1(200, 200);
    // 点的间距
    cout << "distance from pt0 to pt1: "<< bg::distance(pt0, pt1) << endl;

    Segment s1(Point(0, 100), Point(100, 0));
    Segment s2(Point(0, 0), Point(120, 120));
    // 点到线段的距离，垂足不一定在线段上
    cout << "distance from pt0 to s1: " << bg::distance(pt0, s1) << endl;
    // 两线段是否相交
    cout << "Is segment1 and segment2 intersect:  " << bg::intersects(s1, s2) << endl;

    std::list<Point> points;
    // 两线段的交点
    bg::intersection(s1, s2, points);
    for(auto p : points)
    cout << bg::dsv(p) << "  ";
    cout << endl;

    // 判断box是否相交
    Box rc(Point(0, 0), Point(200, 200));
    Box rc0(Point(250, 250), Point(450, 450));
    Box rc1(Point(100, 100), Point(300, 300));

    cout << "rc and rc0 intersect:  " << bg::intersects(rc, rc0) <<endl;
    cout << "rc and rc1 intersect:  " << bg::intersects(rc, rc1) <<endl;
    
    // 求外接矩形Bounding Box
    Line line = { {1,1},{2,0},{3,2} };
    Box box;
    bg::envelope(line, box);
    std::cout << bg::dsv(line) << "'s AABB is " << bg::dsv(box) << std::endl;

    return 0;
}

注意直线的初始化和线段是不一样的

参考:
SLAM本质剖析-Boost
boost::geometry简介