What is wrong with my boolinq .orderBy?

Question

So I try next compilable code:

#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;
}

having boolinq header this programm compiles quite fast. Yet it fails uncachably! at runtime with some inner vector assertion error:

enter image description here

problem is:

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

is empty vector.

uncommenting stl code makes programm work as expected!

futher more simple point reordering makes it work as expected:

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};

A really strange bug...

btw next code:

#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;
}

Produces:

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

What is wrong with my code? It looks alike orderBy examples thay provide on main boolinq page...?

@NicolBolas with the library he linked to: https://code.google.com/p/boolinq/ — Jorge Israel Peña, Mar 15 '13 at 00:04

score 2 · Answer 1 · answered Mar 16 '13 at 20:47

2

Apparently boolinq does not support .orderBy().reverse() - which is somewhat worrying, granted. If you sort by the negative distance (without reverse), it works.

To me this looks like boolinq isn't ready for serious use.

answered Mar 16 '13 at 20:47

Eamon Nerbonne

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yet reverse (with no orderBy) works... it is really sad.. because with linq use vector use would get really much simpler... – myWallJSON Mar 16 '13 at 20:57
consider that orderBy isn't a critical feature - you can always save to a temp. vector and simply sort. Since that's what happens behind the scenes anyhow, it's not such a bad idea - and then you can a different, non-booLinq C++ range implementation (such as boost ranges) that's more robust but happens not to implement orderby – Eamon Nerbonne Mar 21 '13 at 14:32

What is wrong with my boolinq .orderBy?

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