Sierpinski square curve: Difference between revisions

=={{header|ALGOL W}}==

Draws an ASCII art Sierpinski square curve. For orders greater than 6, the value of CANVAS_WIDTH must be increased.<br>

The resolution of the canvas is, of course fairly small, so for orders > 4, to avoid the curve overwriting itself, the connecting lines between the segments of the curve are made longer.

<syntaxhighlight lang="algolw">

begin % draw a Sierpinski curve using ascii art %

integer CANVAS_WIDTH;

CANVAS_WIDTH := 200;

begin

% the ascii art canvas and related items %

string(1) array canvas ( 1 :: CANVAS_WIDTH, 1 :: CANVAS_WIDTH );

integer heading, asciiX, asciiY, width, maxX, maxY, minX, minY;

% draw a line using ascii art - the length is ignored and the heading determines the %

% character to use %

% the position is updated %

procedure drawLine( real value length ) ;

begin

% stores the min and max coordinates %

procedure updateCoordinateRange ;

begin

if asciiX > maxX then maxX := asciiX;

if asciiY > maxY then maxY := asciiY;

if asciiX < minX then minX := asciiX;

if asciiY < minY then minY := asciiY

end updateCoordinateRange ;

if heading = 0 then begin

asciiX := asciiX + 1;

canvas( asciiX, asciiY ) := "_";

updateCoordinateRange;

end

else if heading = 90 then begin

updateCoordinateRange;

canvas( asciiX, asciiY ) := "|";

asciiY := asciiY - 1;

end

else if heading = 180 then begin

asciiX := asciiX - 1;

canvas( asciiX, asciiY ) := "_";

updateCoordinateRange;

end

else if heading = 270 then begin

asciiY := asciiY + 1;

updateCoordinateRange;

canvas( asciiX - 1, asciiY ) := "|";

end if_various_headings

end drawLine ;

% changes the heading by the specified angle ( in degrees ) - angle must be +/- 90 %

% the position is updated, if necessary as the horizontal lines are at the bottom %

% of a character but the vertical lines are in the middle pf a character %

procedure turn( integer value angle ) ;

begin

integer prevHeading;

prevHeading := heading;

heading := heading + angle;

while heading < 0 do heading := heading + 360;

heading := heading rem 360;

if heading = 0 and prevHeading = 270 then asciiX := asciiX - 1

else if heading = 90 then begin

if prevHeading = 180 then asciiX := asciiX - 1

else if prevHeading = 0 then asciiX := asciiX + 1

end

else if heading = 180 and prevHeading = 270 then asciiX := asciiX - 1

else if heading = 270 and prevHeading = 0 then asciiX := asciiX + 2

end turn ;

% initialises the ascii art canvas %

procedure initArt ( integer value initHeading ) ;

begin

heading := initHeading;;

asciiX := CANVAS_WIDTH div 2;

asciiY := asciiX;

maxX := asciiX;

maxY := asciiY;

minX := asciiX;

minY := asciiY;

for x := 1 until CANVAS_WIDTH do for y := 1 until CANVAS_WIDTH do canvas( x, y ) := " "

end initArt ;

% shows the used parts of the canvas %

procedure drawArt ;

begin

for y := minY until maxY do begin

write();

for x := minX until maxX do writeon( canvas( x, y ) )

end for_y ;

write()

end drawIArt ;

% draws a sierpinski square curve of the specified order %

procedure sierpinskiSquareCurve( integer value order ) ;

begin

% draw a line connecting segments %

procedure extendedLine ;

if actualOrder > 4 then begin

% for higher orders, the segments can touch %

% so space the segments further apart %

if heading rem 180 = 0 then drawline( 1 );

drawline( 1 );

drawline( 1 )

end extendedLine ;

% draw a corner of an element of the curve %

procedure corner ;

begin

drawline( 1 );

turn( - 90 );

drawline( 1 )

end corner ;

% recursively draws a part of a sierpinski square curve %

procedure subCurve( integer value order; logical value threeSubCurves ) ;

begin

corner;

turn( + 90 );

drawline( 1 );

if order < 1 then begin

turn( - 90 );

drawline( 1 );

turn( - 90 )

end

else begin

extendedLine;;

turn( + 90 );

curve( order, threeSubCurves );

turn( + 90 );

extendedLine

end if_order_lt_1 ;

drawline( 1 );

turn( + 90 )

end subCurve;

% recursively draws a segment of the sierpinski curve %

procedure curve( integer value order; logical value threeSubCurves ) ;

begin

subCurve( if threeSubCurves then order - 1 else 0, not threeSubCurves );

subCurve( order - 1, not threeSubCurves );

subCurve( if threeSubCurves then order - 1 else 0, not threeSubCurves );

corner

end curve ;

integer actualOrder;

actualOrder := order;

if order = 1 then begin

for c := 1 until 4 do corner

end

else if order = 2 then begin

for c := 1 until 4 do subCurve( 0, false )

end

else begin

for c := 1 until 4 do subCurve( ( 2 * order ) - 5, false )

end if_order_eq_1__2__

end sierpinskiSquareCurve ;

% draw curves %

begin

integer order;

i_w := 1; s_w := 0; % set output formatting %

write( "order> " );

read( order );

write( "Sierpinski curve of order ", order );

write( "===========================" );

write();

initArt( 0 );

sierpinskiSquareCurve( order );

drawArt

end

end

end.

</syntaxhighlight>

{{out}}

<pre>

order> 4

Sierpinski square curve of order 4

==================================

_

_| |_

_| |_

|_ _|

_ |_ _| _

_| |_ _| |_ _| |_

_| |_| |_| |_

|_ _ _ _|

_ |_ _| |_ _| |_ _| _

_| |_ |_| _| |_ |_| _| |_

_| |_ _| |_ _| |_

|_ _| |_ _| |_ _|

_ |_ _| _ |_ _| _ |_ _| _

_| |_ _| |_ _| |_ _| |_ _| |_ _| |_ _| |_

_| |_| |_| |_| |_| |_| |_| |_

|_ _ _ _ _ _ _ _|

|_ _| |_ _| |_ _| |_ _| |_ _| |_ _| |_ _|

|_| _| |_ |_| _| |_ |_| _| |_ |_|

_| |_ _| |_ _| |_

|_ _| |_ _| |_ _|

|_ _| _ |_ _| _ |_ _|

|_| _| |_ _| |_ _| |_ |_|

_| |_| |_| |_

|_ _ _ _|

|_ _| |_ _| |_ _|

|_| _| |_ |_|

_| |_

|_ _|

|_ _|

|_|

</pre>