KP>{
KP>   double a = 0.014390783999999978;
KP>   double b = 0.052996730719235739;
KP>   double c = a - b; //-0.038605946719235763
   
KP>   assert((b+c) == a); //b+c = 0.014390783999999976
KP>}
KP>

#include <cassert>

double sum(double u, double v, double& t) {
    double s = u + v;
    double up = s - v;
    double vpp = s - up;
    up -= u;
    vpp -= v;
    t = -(up + vpp);

    return s;
}

int main()
{
    double a = 0.014390783999999978;
    double b = 0.052996730719235739;

    double err;
    const auto c = sum(a, -b, err);

    assert((b+c) + err == a); //b+c = 0.014390783999999976                                                                                                                    
}