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Reference for unit 'fpg_base' (#fpgui)

TfpgPoint.ManhattanLength

Quick calculation of the length between points

Declaration

Source position: line 0

function TfpgPoint.ManhattanLength: Integer; function TfpgPoint.ManhattanLength(

const PointB: TfpgPoint

):Integer;

Description

Returns the sum of the absolute values of X and Y, traditionally known as the "Manhattan length" of the vector from the origin to the point. For example:

var
  oldPosition: TfpgPoint;
  newPosition: TfpgPoint;
begin
  newPosition := MousePosition - oldPosition;
  if (newPosition.ManhattanLength > 5) then
  begin
    // the mouse has moved more than 5 pixels since the oldPosition
  end;
end;

Accuracy is traded for speed. This is a useful, and quick to calculate, approximation to the true length:

TrueLength := sqrt(power(X, 2) + power(Y, 2));

The tradition of "Manhattan length" arises because such distances apply to travelers who can only travel on a rectangular grid, like the streets of Manhattan.

For a further explanation of "Manhattan length" see the Wikipedia article on Taxicab geometry.