[英]How to input of an set of points elegantly
我想在庫中輸入一組點,其中每個點都包含一組坐標。 我希望輸入內容對於庫的用戶如何選擇代表其數據盡可能地靈活。
所以我希望能夠調用以下偽代碼
template<int dimenension> //the dimension of each of the points
struct set_of_points
{
void insert(Iterator first_point, Iterator last_point);
}
從以下任何一項,
struct set_of_points<2> s;
double points1[3][2] = {
{1,2},
{2,3},
{4,5}
};
s.insert(points1, points1+3);
double p1[2] = {1,2}, p2[2] = {2,3}, p3[2] = {4,5};
double* points2[3] = {p1,p2,p3};
s.insert(points2, points2+3);
std::vector<double*> points3;
points3[0] = p1; points3[1] = p2; points3[2] = p3;
s.insert(points3.begin(), points3.end())
我也可以將vector<vector<double> >
和vector< boost::array<double,2> >
到該列表中。
我能想到的唯一方法是使用擴展的,丑陋的和手工制作的模板魔術。 例如,可以像這樣完成數組的指針和指針。
#include<iostream>
#include <boost/utility/enable_if.hpp>
#include <boost/type_traits/is_array.hpp>
#include <boost/type_traits/is_pointer.hpp>
#include <boost/mpl/if.hpp>
#include <boost/type_traits/remove_pointer.hpp>
#include <boost/mpl/and.hpp>
#include <boost/mpl/or.hpp>
template<int dimenension> //the dimension of each of the points
struct set_of_points
{
// The coordinates of each point are represented as an array or a set of pointers,
// And each point is in an array.
template<typename PointsItr>
void
insert(PointsItr P_begin, PointsItr P_end,
typename boost::enable_if< //enable if
typename boost::mpl::and_<
boost::is_pointer< PointsItr >, //The set of points is a pointer, AND
typename boost::mpl::or_< //either
boost::is_array<typename boost::remove_pointer< PointsItr >::type >, //The points are an array
boost::is_pointer<typename boost::remove_pointer< PointsItr >::type > //or are pointers
>::type //close or
>::type //close and
>::type* dummy = 0)
{
std::cout<<"inserted pointer of (pointers OR array)"<<std::endl;
}
};
int
main (int ac, char **av)
{
struct set_of_points<2> s;
double points1[3][2] = {
{1,2},
{2,3},
{4,5}
};
s.insert(points1, points1+3);
double p1[2] = {1,2}, p2[2] = {2,3}, p3[2] = {4,5};
double* points2[3] = {p1,p2,p3};
s.insert(points2, points2+3);
}
Yu 有沒有一種可維護的方式來做到這一點? 如果沒有,是否有辦法以某種方式將模板噪音整理到庫中,因此我不必為我編寫的每個容器編寫此類代碼。
好吧,找不到一種優雅的方式來做到這一點。
這是我到目前為止獲得的解決方案,它似乎涵蓋了大多數基礎知識:
#include<iostream>
#include <boost/utility/enable_if.hpp>
#include <boost/type_traits/is_array.hpp>
#include <boost/type_traits/is_pointer.hpp>
#include <boost/type_traits/is_class.hpp>
#include <boost/type_traits/remove_pointer.hpp>
#include <boost/mpl/and.hpp>
#include <boost/mpl/or.hpp>
#include <boost/array.hpp>
#include <vector>
template<int dimenension> //the dimension of each of the points
struct set_of_points
{
// The coordinates of each point are represented as an array or a set of pointers,
// And each point is in an array.
template<typename PointsItr>
void
insert(PointsItr P_begin, PointsItr P_end,
typename boost::enable_if< //enable if
typename boost::mpl::and_<
boost::is_pointer< PointsItr >, //The set of points is a pointer, AND
typename boost::mpl::or_< //either
boost::is_array<typename boost::remove_pointer< PointsItr >::type >, //The points are an array
boost::is_pointer<typename boost::remove_pointer< PointsItr >::type > //or are pointers
>::type //close or
>::type //close and
>::type* dummy = 0)
{
//get the type of the array
std::cout<<"inserted pointer of (pointers OR array)"<<std::endl;
}
// The coordinates of each point are represented as an array or a set of pointers,
// And each point is in a container.
template<typename PointsItr>
void
insert(PointsItr P_begin, PointsItr P_end,
typename boost::enable_if< //enable if
typename boost::mpl::and_<
boost::is_pointer< PointsItr >, //The set of points is a pointer, AND
boost::is_class<typename boost::remove_pointer< PointsItr >::type> //The points are wrapped in a class, assume has a begin and end method
>::type //close and
>::type* dummy = 0)
{
//get the type of the array
std::cout<<"inserted pointer of container"<<std::endl;
}
// The coordinates of each point are represented as a class,
// And each point is an array or pointer
template<typename PointsItr>
void
insert(PointsItr P_begin, PointsItr P_end,
typename boost::enable_if< //enable if
typename boost::mpl::and_<
boost::is_class< PointsItr >, //The set of points is a class, AND
typename boost::mpl::or_< //either
boost::is_array<typename PointsItr::value_type >, //The points are an array
boost::is_pointer<typename PointsItr::value_type> //or are pointers
>::type //close or
>::type //close and
>::type* dummy = 0)
{
//get the type of the array
std::cout<<"inserted container of pointers"<<std::endl;
}
// The coordinates of each point are represented as a class,
// And each point is a class
template<typename PointsItr>
void
insert(PointsItr P_begin, PointsItr P_end,
typename boost::enable_if< //enable if
typename boost::mpl::and_<
boost::is_class< PointsItr >, //The set of points is a class, AND
boost::is_class<typename PointsItr::value_type > //The points are a class
>::type //close and
>::type* dummy = 0)
{
//get the type of the array
std::cout<<"inserted container of containers"<<std::endl;
}
};
int
main (int ac, char **av)
{
struct set_of_points<2> s;
double points1[3][2] = {
{1,2},
{2,3},
{4,5}
};
s.insert(points1, points1+3);
double p1[2] = {1,2}, p2[2] = {2,3}, p3[2] = {4,5};
double* points2[3] = {p1,p2,p3};
s.insert(points2, points2+3);
boost::array<double,2> p4,p5,p6;
p4[0] = 1.0; p4[1] = 2.0;
p5[0] = 1.0; p5[1] = 2.0;
p6[0] = 1.0; p6[1] = 2.0;
boost::array<double,2> points3[3] = {p4,p5,p6};
s.insert(points3, points3+3);
std::vector<double*> points4(3);
points4[0]=p1; points4[1]=p2; points4[2]=p3;
s.insert(points4.begin(), points4.end());
std::vector<boost::array<double,2> > points5(3);
points5[0]=p4; points5[1]=p5; points5[2]=p6;
s.insert(points5.begin(), points5.end());
}
沒有標准的方法可以執行您要的操作,因為如果double *表示一個點(如points2,points3),則您不知道數組的大小。 當然,除非您信任庫的用戶提供正確的大小並且不會引起段錯誤(不要這樣做:-))。
但是,如果要允許向量,c樣式雙精度數組或任何雙精度容器表示一個點,請考慮使用BOOST_FOREACH
(或C ++ 11 foreach循環):
template <typename T>
Point MakePoint(const T& pointData)
{
Point p;
BOOST_FOREACH(double& x, pointData)
{
// check p isn't full
p.Add(x);
}
return p;
}
(不必擔心花哨的enable_if東西,BOOST_FOREACH或c ++ 11 foreach將確保T是雙精度容器。)
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