## 18.3 Using The Module GraphPaper

The following module is a demonstration of some simple aspects of the GraphPaper library.

```MODULE TestGraph;

(* by Joel Schwartz 1998 06 12 to test GraphPaper
revised 1998 07 11 by R. Sutcliffe. *)

FROM GraphPaper IMPORT
AngleType, CoordSystem, SetCoordSystem, SetAngleType, SetLabels, SetScale,
ShowAxes, ShowLabels, PlotPoint, PolarPlotPoint, TurnTo, LineBy,
LineTo, MoveTo, Turn, Home;

FROM RealMath IMPORT
pi, sin;

VAR
counter : INTEGER;
x, y : REAL;

PROCEDURE DrawSquare (side : INTEGER);
(* draws a square of the given side length starting at the current angle; concludes with the same position and angle as it started *)
VAR
Count : CARDINAL;
BEGIN
FOR Count := 1 TO 4
DO
LineBy (side);
Turn (pi/2.0);
END;
SetAngleType (deg);
END DrawSquare;

BEGIN
(* Set up the axes *)
SetCoordSystem (standard); (* use mathematical system *)
SetLabels ('X', 'Y');
SetScale (1); (* one dot per division *)
ShowAxes;
ShowLabels;

(* Test the scaled point plotting routines *)
(* Sine curve *)
FOR counter := -4000 TO 4000
DO
x := FLOAT (counter)/100.0;
y := sin (x);
PlotPoint (x, y);
END;

(* Circle of radius 5 units with a point at every unit degree angle *)
FOR counter := 1 TO 360
DO
PolarPlotPoint (5.0, FLOAT (counter));
END;

(* Angled line *)
FOR counter := 1 TO 300
DO
PolarPlotPoint (FLOAT (counter)/10.0 ,10.0);
END;

(* Test the pixel plotting routines *)
Home;
TurnTo (30.0);
LineBy (200);
LineTo (200, -100);
LineBy (100);

(* Make a square *)
TurnTo (0.0);
DrawSquare (75);

SetCoordSystem (MacWin); (* use Mac system *)
MoveTo (0, 0);
TurnTo (60.0);
LineBy (250); (* should come from top left corner *)

SetCoordSystem (bearing); (* use bearing system *)
MoveTo (-60, -60);
Turn (225.0);
LineBy (150); (* should be in bottom left quadrant *)

END TestGraph.```

The reader should verify the correctness of each routine in the following (much reduced) screen shot of the output.

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