1

所以我尝试下一个可编译的代码：

#include <math.h> 
#include <iostream> 
#include <algorithm>
#include <vector>   
#include "boolinq.h"

float dtSqrt(float x)
{
    return sqrtf(x);
}

/// Returns the distance between two points.
///  @param[in]     v1  A point. [(x, y, z)]
///  @param[in]     v2  A point. [(x, y, z)]
/// @return The distance between the two points.
inline float dtVdist(const float* v1, const float* v2)
{
    const float dx = v2[0] - v1[0];
    const float dy = v2[1] - v1[1];
    const float dz = v2[2] - v1[2];
    return dtSqrt(dx*dx + dy*dy + dz*dz);
}

int main () {
    float target[] = {1,2,3};

    float floats1[] = {1.321f,2.123f,3.333f};
    float floats2[] = {1.011f,2.234f,3.555f};
    float floats3[] = {1.9f,2.9f,3.9f};
    float floats4[] = {1,2,3};
    float floats5[] = {1,2,3.123f};

    std::vector<const float *> floatsVector;
    floatsVector.push_back(floats1);
    floatsVector.push_back(floats2);
    floatsVector.push_back(floats3);
    floatsVector.push_back(floats4);
    floatsVector.push_back(floats5);

    //stl way
    //std::sort(floatsVector.begin(), floatsVector.end(),  [&](const float* pointA, const float* pointB) -> bool{
    //  auto distA =  dtVdist(pointA, target);
    //  auto distB =  dtVdist(pointB, target);
    //  return distA < distB;
    //});
    // auto stl_point = floatsVector.front();

    try {
        auto point = boolinq::from( floatsVector )
            .orderBy([&](const float* point) -> float{
                auto dist =  dtVdist(point, target);
                return dist;
        })
            .reverse()
            .toVector()
            .front();

        std::cout << point[0] << " " << point[1] << " " << point[2] << ";" << std::endl;

    } catch (std::exception &e) {
        std::cout << e.what() << std::endl;
    }
    std::cin.get();
    return 0;
}

有boolinq 头这个程序编译得非常快。然而，它失败了！在运行时出现一些内部向量断言错误：

在此处输入图像描述

问题是：

 boolinq::from( floatsVector )
                .orderBy([&](const float* point) -> float{
                    auto dist =  dtVdist(point, target);
                    return dist;
            }).toVector();

是空向量。

取消注释 stl 代码使程序按预期工作！

更简单的点重新排序使其按预期工作：

float floats1[] = {1,2,3};
float floats2[] = {1,2,3.123f};
float floats3[] = {1.321f,2.123f,3.333f};
float floats4[] = {1.011f,2.234f,3.555f};
float floats5[] = {1.9f,2.9f,3.9f};

一个非常奇怪的错误...

顺便说一句，下一个代码：

#include <math.h> 
#include <iostream> 
#include <algorithm>
#include <vector>   
#include "boolinq/boolinq.h"

struct Point {
    float X;
    float Y;
    float Z;
    Point() : X(0), Y(0), Z(0) {}
    Point(float X, float Y, float Z) : X(X), Y(Y), Z(Z) {}
};

float dtSqrt(float x)
{
    return sqrtf(x);
}

inline float dtVdist(const float* v1, const float* v2)
{
    const float dx = v2[0] - v1[0];
    const float dy = v2[1] - v1[1];
    const float dz = v2[2] - v1[2];
    return dtSqrt(dx*dx + dy*dy + dz*dz);
}

inline float dtVSqrDist(const Point & v1, const Point & v2)
{
    const float dx = v2.X - v1.X;
    const float dy = v2.Y - v1.Y;
    const float dz = v2.Z - v1.Z;
    return dx*dx + dy*dy + dz*dz;
}

int main () {
    auto target = Point(1,2,3);
    auto pointA = Point(1,-2,3);
    auto pointB = Point(1,2,3);

    std::vector<Point> pointsVector;
    pointsVector.push_back(pointA);
    pointsVector.push_back(pointB);

    //stl way
    std::sort(pointsVector.begin(), pointsVector.end(),
        [&](const Point & pointA, const Point & pointB) -> bool{
            auto distA =  dtVSqrDist(pointA, target);
            auto distB =  dtVSqrDist(pointB, target);
            return distA < distB;
    });
    std::reverse(pointsVector.begin(), pointsVector.end());
    auto stl_point = pointsVector.front();

    std::cout << "stl point: " << stl_point.X << " " << stl_point.Y << " " << stl_point.Z << ";" << std::endl;

    //try {

    auto points = boolinq::from( pointsVector )
        .orderBy([&](const Point & point) -> float{
            auto dist =  dtVSqrDist(point, target);
            return dist;
    })
        .reverse()
        .toVector();

    auto point = points.empty() ? Point() : points.front();

    std::cout << "boolinq point: " << point.X << " " << point.Y << " " << point.Z << ";" << std::endl;

    //} catch (std::exception &e) {
    //  std::cout << e.what() << std::endl;
    //}
    std::cin.get();
    return 0;
}

产生：

stl point: 1 -2 3;
boolinq point: 0 0 0;

我的代码有什么问题？它看起来像在主 boolinq 页面上提供的 orderBy 示例...？

4

1 回答 1

2

显然 boolinq 不支持 .orderBy().reverse() - 这有点令人担忧，当然。如果您按负距离排序（没有反向），它可以工作。

对我来说，这看起来像 boolinq 还没有准备好认真使用。

于 2013-03-16T20:47:15.730 回答