Simple turtle graphics
The first turtle graphic discussed in Mindstorms: Children, Computers, and Powerful Ideas by Seymour Papert is a simple drawing of a house. It is a square with a triangle on top for the roof.
For a slightly more advanced audience, a more practical introduction to turtle graphics might be to draw a bar chart.
See image here: https://i.imgur.com/B7YbTbZ.png
- Task
-
- Create a function (or subroutine) that uses turtle graphics to draw a house of a specified size as described above. Optionally make it lovely by adding details such as, for example, doors and windows.
- Create a function (or subroutine) that takes a list (array, vector) of non-negative numbers and draws a bar chart from them, scaled to fit exactly in a square of a specified size. The enclosing square need not be drawn.
- Both functions should return the turtle to the location it was at and facing in the same direction as it was immediately before the function was executed.
Julia
Outputs a PNG file. <lang julia>using Luxor, Colors
function house(π’, x, y, siz)
oldorientation = π’.orientation xpos, ypos = π’.xpos, π’.ypos # house wall Reposition(π’, x, y) Rectangle(π’, siz, siz) # roof Reposition(π’, x - siz / 2, y - siz / 2) Turn(π’, -60) Forward(π’, siz) Turn(π’, 120) Forward(π’, siz) # turtle_demo doorheight, doorwidth = siz / 2, siz / 4 Pencolor(π’, 0, 0, 0) Reposition(π’, x, y + doorheight / 2) Rectangle(π’, doorwidth, doorheight) # window windowheight, windowwidth = siz /3, siz / 4 Reposition(π’, x + siz / 4, y - siz / 4) Rectangle(π’, windowwidth, windowheight) Reposition(π’, x - siz / 4, y - siz / 4) Rectangle(π’, windowwidth, windowheight) Orientation(π’, oldorientation) Reposition(π’, xpos, ypos)
end
function barchart(π’, data, x, y, siz)
oldorientation = π’.orientation xpos, ypos = π’.xpos, π’.ypos maxdata = maximum(data) # scale to fit within a square with sides `siz` and draw bars of chart barwidth = siz / length(data) Pencolor(π’, 1.0, 0.0, 0.5) Reposition(π’, x, y) for n in data # draw each bar in chart barheight = n * siz / maxdata Reposition(π’, x, y - barheight / 2) Rectangle(π’, barwidth, barheight) x += barwidth end Orientation(π’, oldorientation) Reposition(π’, xpos, ypos)
end
function testturtle(width = 400, height = 600)
dra = Drawing(600, 400, "turtle_demo.png") origin() background("midnightblue") π’ = Turtle() Pencolor(π’, "cyan") Penwidth(π’, 1.5) house(π’, -width / 3, height / 7, width / 2) barchart(π’, [15, 10, 50, 35, 20], width / 8, height / 8, width / 2) finish()
end
testturtle() </lang>
Logo
<lang Logo>to rectangle :width :height
repeat 2 [ forward :height left 90 forward :width left 90 ] end
to square :size
rectangle size size end
to triangle :size
repeat 3 [ forward size right 120 ] end
to house :size
left 90 square size triangle size right 90 end
to max :lst
if equalp count lst 1 [ output first lst ] make "x max butfirst lst if x > first lst [ output x ] output first lst end
to barchart :lst :size
right 90 if emptyp lst [ stop ] make "scale size / (max lst) make "width size / count lst foreach lst [ rectangle ? * scale width forward width ] back size left 90 end
clearscreen hideturtle house 150 penup right 90 forward 10 left 90 pendown barchart [ 0.5 0.33333 2 1.3 0.5 ] 200 left 90 back 10 right 90</lang>
- Output:
Python
<lang Python>from turtle import *
def rectangle(width, height):
for _ in range(2): forward(height) left(90) forward(width) left(90)
def square(size):
rectangle(size, size)
def triangle(size):
for _ in range(3): forward(size) right(120)
def house(size):
right(180) square(size) triangle(size) right(180)
def barchart(lst, size):
scale = size/max(lst) width = size/len(lst) for i in lst: rectangle(i*scale, width) penup() forward(width) pendown() penup() back(size) pendown()
clearscreen() hideturtle() house(150) penup() forward(10) pendown() barchart([0.5, (1/3), 2, 1.3, 0.5], 200) penup() back(10) pendown()</lang>
- Output:
Quackery
<lang Quackery> [ $ "turtleduck.qky" loadfile ] now!
[ behead do rot witheach [ do 2over 2over v< if 2swap 2drop ] ] is largest ( [ --> n/d )
[ 2 times [ 2dup walk -1 4 turn 2over walk -1 4 turn ] 2drop 2drop ] is rectangle ( n/d n/d --> )
[ 2dup rectangle ] is square ( n/d --> )
[ 3 times [ 2dup walk 1 3 turn ] 2drop ] is triangle ( n/d --> )
[ 1 2 turn 2dup square triangle 1 2 turn ] is house ( n/d --> )
[ stack ] is bar.width ( --> s )
[ stack ] is bar.scale ( --> s )
[ join temp put dup size n->v temp share do v/ 1/v join bar.width put dup largest temp share do v/ join bar.scale put witheach [ do bar.scale share do v/ bar.width share do rectangle bar.width share do fly ] temp take do -v fly bar.width release bar.scale release ] is barchart ( [ n/d --> )
turtle 150 1 house 10 1 fly ' [ [ 1 2 ] [ 1 3 ] [ 2 1 ] [ 13 10 ] [ 1 2 ] ] 200 1 barchart -10 1 fly</lang>
- Output:
Wren
<lang ecmascript>import "dome" for Window import "graphics" for Canvas, Color import "./turtle" for Turtle
class Main {
construct new(width, height) { Window.resize(width, height) Canvas.resize(width, height) Window.title = "Simple turtle graphics" _w = width _h = height }
init() { Canvas.cls(Color.white) _t = Turtle.new() drawHouse(_w/4) barChart([15, 10, 50, 35, 20], _w/3) }
drawHouse(size) { // save initial turtle position and direction var saveX = _t.x var saveY = _t.y var saveD = _t.dir _t.pen.width = 2
// draw house _t.drawRect(_w/4, _h/2, size, size)
// draw roof _t.right(30) _t.walk(size) _t.right(120) _t.walk(size)
// draw door var doorWidth = (size/4).floor var doorHeight = (size/2).floor _t.drawRect(_w/4 + doorWidth/2, _h/2 + doorHeight, doorWidth, doorHeight)
// draw window var windWidth = (size/3).floor var windHeight = (size/4).floor _t.drawRect(_w/4 + size/2, _h/2 + size/2, windWidth, windHeight)
// restore initial turtle position and direction _t.x = saveX _t.y = saveY _t.dir = saveD }
// nums assumed to be all non-negative barChart(nums, size) { // save intial turtle position and direction var saveX = _t.x var saveY = _t.y var saveD = _t.dir
// find maximum var max = 0 for (n in nums) if (n > max) max = n
// scale to fit within a square with sides 'size' and draw chart var barWidth = (size / nums.count).floor var startX = _w / 2 + 20 var startY = _h / 2 for (i in 0...nums.count) { var barHeight = (nums[i] * size / max).round _t.drawRect(startX, startY - barHeight, barWidth, barHeight) startX = startX + barWidth }
// restore intial turtle position and direction _t.x = saveX _t.y = saveY _t.dir = saveD }
update() {}
draw(alpha) {}
}
var Game = Main.new(600, 600)</lang>
- Output:
Similar to Quackery image except that the house has a door and a single window.