geometry_help.h

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#ifndef NAV_2D_UTILS_GEOMETRY_HELP_H
#define NAV_2D_UTILS_GEOMETRY_HELP_H

#include <cmath>

namespace nav_2d_utils
{
inline double distanceToLine(double pX, double pY, double x0, double y0, double x1, double y1)
{
  double A = pX - x0;
  double B = pY - y0;
  double C = x1 - x0;
  double D = y1 - y0;

  double dot = A * C + B * D;
  double len_sq = C * C + D * D;
  double param = dot / len_sq;

  double xx, yy;

  if (param < 0)
  {
    xx = x0;
    yy = y0;
  }
  else if (param > 1)
  {
    xx = x1;
    yy = y1;
  }
  else
  {
    xx = x0 + param * C;
    yy = y0 + param * D;
  }

  return hypot(pX - xx, pY - yy);
}
}  // namespace nav_2d_utils

#endif  // NAV_2D_UTILS_GEOMETRY_HELP_H