Dragon curve: Difference between revisions
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Algol 68 →L-System: comments
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=={{header|ALGOL 68}}==
===Animated===
{{trans|python}}
<!-- {{works with|ALGOL 68|Standard - but ''draw'' is not part of the standard prelude}} -->
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|}
Note: each Dragon curve is composed of many smaller dragon curves (shown in a different colour).
===L-System===
Alternative (monochrome) version using the L-System library.
{{libheader|ALGOL 68-l-system}}
Generates an SVG file containing the curve using the L-System. Very similar to the Algol 68 Sierpinski square curve sample. Note the Algol 68 L-System library source code is on a separate page on Rosetta Code - follow the above link and then to the Talk page.
<syntaxhighlight lang="algol68">
BEGIN # Dragon Curve in SVG #
# uses the RC Algol 68 L-System library for the L-System evaluation & #
# interpretation #
PR read "lsystem.incl.a68" PR # include L-System utilities #
PROC dragon curve = ( STRING fname, INT size, length, order, init x, init y )VOID:
IF FILE svg file;
BOOL open error := IF open( svg file, fname, stand out channel ) = 0
THEN
# opened OK - file already exists and #
# will be overwritten #
FALSE
ELSE
# failed to open the file #
# - try creating a new file #
establish( svg file, fname, stand out channel ) /= 0
FI;
open error
THEN # failed to open the file #
print( ( "Unable to open ", fname, newline ) );
stop
ELSE # file opened OK #
REAL x := init x;
REAL y := init y;
INT angle := 0;
put( svg file, ( "<svg xmlns='http://www.w3.org/2000/svg' width='"
, whole( size, 0 ), "' height='", whole( size, 0 ), "'>"
, newline, "<rect width='100%' height='100%' fill='white'/>"
, newline, "<path stroke-width='1' stroke='black' fill='none' d='"
, newline, "M", whole( x, 0 ), ",", whole( y, 0 ), newline
)
);
LSYSTEM ssc = ( "F"
, ( "F" -> "F+S"
, "S" -> "F-S"
)
);
STRING curve = ssc EVAL order;
curve INTERPRET ( ( CHAR c )VOID:
IF c = "F" OR c = "S" THEN
x +:= length * cos( angle * pi / 180 );
y +:= length * sin( angle * pi / 180 );
put( svg file, ( " L", whole( x, 0 ), ",", whole( y, 0 ), newline ) )
ELIF c = "+" THEN
angle +:= 90 MODAB 360
ELIF c = "-" THEN
angle -:= 90 MODAB 360
FI
);
put( svg file, ( "'/>", newline, "</svg>", newline ) );
close( svg file )
FI # sierpinski square # ;
dragon curve( "dragon.svg", 1200, 5, 12, 400, 200 )
END
</syntaxhighlight>
=={{header|AmigaE}}==
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Valid coordinates on the TI-89's graph screen are x 0..76 and y 0..158. This and [[wp:File:Dimensions_fractale_dragon.gif|the outer size of the dragon curve]] were used to choose the position and scale determined by the [[wp:Transformation_matrix#Affine_transformations|transformation matrix]] initially passed to <code>dragon</code> such that the curve will fit onscreen no matter the number of recursions chosen. The height of the curve is 1 unit, so the vertical (and horizontal, to preserve proportions) scale is the height of the screen (rather, one less, to avoid rounding/FP error overrunning), or 75. The curve extends 1/3 unit above its origin, so the vertical translation is (one more than) 1/3 of the scale, or 26. The curve extends 1/3 to the left of its origin, or 25 pixels; the width of the curve is 1.5 units, or 1.5·76 = 114 pixels, and the screen is 159 pixels, so to center it we place the origin at 25 + (159-114)/2 = 47 pixels.
==={{header|uBasic/4tH}}===
{{Trans|BBC BASIC}}
uBasic/4tH has neither native support for graphics nor floating point, so everything has to be defined in high level code. All calculations are done in integer arithmetic, scaled by 10K.
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EndIf
' draw a line
Proc _Line (a, b, Set (a, a + (((-
Return
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_Canvas ' set up a canvas x wide and y high
Param (2)
Write @o(0), "<svg width=\q";a@;"\q height=\q";b@;"\q viewBox=\q0 0 ";a@;" ";b@;
Write @o(0), "\q xmlns=\qhttp://www.w3.org/2000/svg\q ";
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IF A@ THEN PUSH -POP()
RETURN
' return COS(x*10K), scaled by 10K
_COS PARAM(1) : PUSH ABS(A@%62832) : IF TOS()>31416 THEN PUSH 62832-POP()
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'''Solution'''
=== Recursive ===
[[File:Fōrmulæ - Dragon curve 01.png]]
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[[File:Fōrmulæ - Dragon curve 03.png]]
=== L-system ===
There are generic functions written in Fōrmulæ to compute an L-system in the page [[L-system#Fōrmulæ | L-system]].
The program that creates a Dragon curve is:
[[File:Fōrmulæ - L-system - Dragon curve 01.png]]
[[File:Fōrmulæ - L-system - Dragon curve 02.png]]
Rounded version:
[[File:Fōrmulæ - L-system - Dragon curve (rounded) 01.png]]
[[File:Fōrmulæ - L-system - Dragon curve (rounded) 02.png]]
=={{header|Gnuplot}}==
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{{trans|Kotlin}}
{{libheader|DOME}}
<syntaxhighlight lang="
import "dome" for Window
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