Sierpinski square curve: Difference between revisions
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Produce a graphical or ASCII-art representation of a [[wp:Sierpiński_curve|Sierpinski square curve]] of at least order 3.
=={{header|Go}}==
{{libheader|Go Graphics}}
{{libheader|go-lindenmayer}}
The following uses the Lindenmayer system with the appropriate parameters from the Wikipedia article and produces a similar image (apart from the colors, yellow on blue) to the Sidef and zkl entries.
<lang go>package main
import (
"github.com/fogleman/gg"
"github.com/trubitsyn/go-lindenmayer"
"log"
"math"
)
const twoPi = 2 * math.Pi
var (
width = 770.0
height = 770.0
dc = gg.NewContext(int(width), int(height))
)
var cx, cy, h, theta float64
func main() {
dc.SetRGB(0, 0, 1) // blue background
dc.Clear()
cx, cy = 10, height/2+5
h = 6
sys := lindenmayer.Lsystem{
Variables: []rune{'X'},
Constants: []rune{'F', '+', '-'},
Axiom: "F+XF+F+XF",
Rules: []lindenmayer.Rule{
{"X", "XF-F+F-XF+F+XF-F+F-X"},
},
Angle: math.Pi / 2, // 90 degrees in radians
}
result := lindenmayer.Iterate(&sys, 5)
operations := map[rune]func(){
'F': func() {
newX, newY := cx+h*math.Sin(theta), cy-h*math.Cos(theta)
dc.LineTo(newX, newY)
cx, cy = newX, newY
},
'+': func() {
theta = math.Mod(theta+sys.Angle, twoPi)
},
'-': func() {
theta = math.Mod(theta-sys.Angle, twoPi)
},
}
if err := lindenmayer.Process(result, operations); err != nil {
log.Fatal(err)
}
// needed to close the square at the extreme left
operations['+']()
operations['F']()
// create the image and save it
dc.SetRGB255(255, 255, 0) // yellow curve
dc.SetLineWidth(2)
dc.Stroke()
dc.SavePNG("sierpinski_square_curve.png")
}</lang>
=={{header|Perl}}==
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