box.hpp

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#pragma once
 
#include "vec.hpp"
 
namespace pa {
 
struct Box {
    vec upperbound;
    vec lowerbound;
};
 
template <class Vec>
inline auto project(const Vec &v,  
                    const Box &box 
) {
    using binary_real_f = real_t (*)(real_t, real_t);
    return v.binaryExpr(box.lowerbound, binary_real_f(std::fmax))
        .binaryExpr(box.upperbound, binary_real_f(std::fmin));
}
 
template <class Vec>
inline auto
projecting_difference(const Vec &v,  
                      const Box &box 
) {
    return v - project(v, box);
}
 
inline real_t dist_squared(crvec v,       
                           const Box &box 
) {
    return projecting_difference(v, box).squaredNorm();
}
 
inline real_t dist_squared(crvec v,        
                           const Box &box, 
                           crvec Σ 
) {
    // TODO: Does this allocate?
    //       Does it have dangling references to temporaries?
    auto d = v - project(v, box);
    return d.dot(Σ.asDiagonal() * d);
}
 
} // namespace pa