in reply to Check if line is straight

If you really want to check colinearity of three points, you can just multiply vectors:
sub isCorrectPath () { my ($x1, $y1, $x2, $y2, $x, $y) = @_; return !(($x2-$x1)*($y-$y1)-($x-$x1)*($y2-$y1)); }

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Re^2: Check if line is straight
by Anonymous Monk on May 16, 2011 at 20:14 UTC
    This is pretty neat, saves a lot of code. What is the best way to add tolerance to this? any suggestions ? Thanks
      return abs(($x2-$x1)*($y-$y1)-($x-$x1)*($y2-$y1)) < $tolerance;

      Update added abs()

      It depends if you mean tolerance necessary for dealing floats - lidden suggested it already. But if you mean real tolerance, for instance "path is correct if the angle between two vectors is less than 1 degree", you should really compute that value.