%% Copyright (c) 2011, INRA
%% 2003-2011, David Legland <david.legland@grignon.inra.fr>
%% 2011 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
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%% -*- texinfo -*-
%% @deftypefn {Function File} {@var{b} = } isPointOnLine (@var{point}, @var{line})
%% Test if a point belongs to a line
%%
%%   B = isPointOnLine(POINT, LINE)
%%   with POINT being [xp yp], and LINE being [x0 y0 dx dy].
%%   Returns 1 if point lies on the line, 0 otherwise.
%%
%%   If POINT is an N*2 array of points, B is a N*1 array of booleans.
%%
%%   If LINE is a N*4 array of line, B is a 1*N array of booleans.
%%
%%   @seealso {lines2d, points2d, isPointOnEdge, isPointOnRay, angle3Points}
%% @end deftypefn

function b = isPointOnLine(point, line, varargin)
 
  % extract computation tolerance
  tol = 1e-14;
  if ~isempty(varargin)
      tol = varargin{1};
  end

  % number of lines and of points
  Nl = size(line, 1);
  Np = size(point, 1);

  % adapt the size of inputs
  x0 = repmat(line(:,1)', Np, 1);
  y0 = repmat(line(:,2)', Np, 1);
  dx = repmat(line(:,3)', Np, 1);
  dy = repmat(line(:,4)', Np, 1);
  xp = repmat(point(:,1), 1, Nl);
  yp = repmat(point(:,2), 1, Nl);

  % test if lines are colinear
  b = abs((xp-x0).*dy-(yp-y0).*dx)./hypot(dx, dy) < tol;

endfunction