Simple turtle graphics
Simple turtle graphics is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
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(🐢, x, y, siz)
oldorientation = 🐢.orientation xpos, ypos = 🐢.xpos, 🐢.ypos # house wall Reposition(🐢, x, y) Rectangle(🐢, siz, siz) # roof Reposition(🐢, x - siz / 2, y - siz / 2) Turn(🐢, -60) Forward(🐢, siz) Turn(🐢, 120) Forward(🐢, siz) # turtle_demo doorheight, doorwidth = siz / 2, siz / 4 Pencolor(🐢, 0, 0, 0) Reposition(🐢, x, y + doorheight / 2) Rectangle(🐢, doorwidth, doorheight) # window windowheight, windowwidth = siz /3, siz / 4 Reposition(🐢, x + siz / 4, y - siz / 4) Rectangle(🐢, windowwidth, windowheight) Reposition(🐢, x - siz / 4, y - siz / 4) Rectangle(🐢, windowwidth, windowheight) Orientation(🐢, oldorientation) Reposition(🐢, xpos, ypos)
end
function barchart(🐢, data, x, y, siz)
oldorientation = 🐢.orientation
xpos, ypos = 🐢.xpos, 🐢.ypos
maxdata = maximum(data)
# scale to fit within a square with sides `siz` and draw bars of chart
barwidth = siz / length(data)
Pencolor(🐢, 1.0, 0.0, 0.5)
Reposition(🐢, x, y)
for n in data # draw each bar in chart
barheight = n * siz / maxdata
Reposition(🐢, x, y - barheight / 2)
Rectangle(🐢, barwidth, barheight)
x += barwidth
end
Orientation(🐢, oldorientation)
Reposition(🐢, xpos, ypos)
end
function testturtle(width = 400, height = 600)
dra = Drawing(600, 400, "turtle_demo.png")
origin()
background("midnightblue")
🐢 = Turtle()
Pencolor(🐢, "cyan")
Penwidth(🐢, 1.5)
house(🐢, -width / 3, height / 7, width / 2)
barchart(🐢, [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:
Phix
You can run this online here. Note this resizes nicely on the desktop but not yet under pwa/p2js - on that you just get the same size canvas centred.
-- -- demo\rosetta\Simple_turtle_graphics.exw -- ======================================= -- with javascript_semantics include pGUI.e Ihandle canvas, dlg cdCanvas cdcanvas atom x = 0, y = 0, direction = 0 bool pen_down = true procedure walk(atom distance) // // Move forward by distance pixels. // atom start_x = x, start_y = y, angle = direction*PI/180 x += distance*sin(angle) y += distance*cos(angle) if pen_down then cdCanvasLine(cdcanvas,start_x,start_y,x,y) end if end procedure procedure right(atom angle) direction = remainder(direction+angle,360) end procedure procedure left(atom angle) right(360-angle) end procedure procedure penup() pen_down = false end procedure procedure pendown(atom colour=CD_BLACK) pen_down = true cdCanvasSetForeground(cdcanvas, colour) end procedure procedure move(sequence s) -- s is a list of angles (odd elements) -- and distances (even elements) for i=1 to length(s) do if odd(i) then right(s[i]) else walk(s[i]) end if end for end procedure procedure rectangle(atom width, height) move({0,height,90,width,90,height,90,width,90}) end procedure procedure draw_house(atom width, height) // // Draw a house at the current x,y // direction must be 0 for house to be upright // // house walls rectangle(width, height) // door (maybe some windows too would be nice...) penup() move({90,width/7,-90}) pendown(CD_BLUE) rectangle(width/8,height/2.5) penup() move({-90,width/7,90}) // roof walk(height) pendown(CD_RED) atom a = arctan(width/height)*CD_RAD2DEG, d = sqrt(width*width+height*height)/2 move({a,d,180-a*2,d}) penup() // return to origin({qw,qh}) and direction 0: move({90+a,width,-90,height,180}) end procedure procedure draw_barchart(sequence nums, atom w, h) // draw a barchart occupying the middle 60% of w,h // nums can contain +ve and/or -ve values. integer n = length(nums) atom mx = max(max(nums),0), mn = min(min(nums),0), r = mx-mn, -- range zl = abs(mn)/r*h*0.6+h/5, -- zero line bw = w*0.6/n -- bar width move({90,w/5,-90,zl}) pendown() for i=1 to n do atom ni = nums[i]/r*h*0.6 if ni>0 then rectangle(bw,ni) else pendown(CD_RED) right(90) rectangle(-ni,bw) left(90) pendown(CD_BLACK) end if move({90,bw,-90}) end for penup() // return to origin({w/2,0}) and direction 0: move({180,zl,90,w/5+bw*n,90}) end procedure function redraw_cb(Ihandle /*ih*/, integer /*posx*/, /*posy*/) integer {width, height} = IupGetIntInt(canvas, "DRAWSIZE") cdCanvasActivate(cdcanvas) cdCanvasClear(cdcanvas) atom qw = width/4, qh = height/4 penup() move({0,qh,90,qw,-90}) pendown() draw_house(qw,qh) -- (at current x,y) penup() move({180,qh,90,qw,90}) -- return to {0,0} move({90,width/2,-90}) -- barchart in the right half draw_barchart({0.5, -4/3, 2, 1.3, 0.5},width/2,height) move({-90,width/2,90}) -- return to {0,0} -- sanity checks if round(x)!=0 then ?9/0 end if if round(y)!=0 then ?9/0 end if if round(direction)!=0 then ?9/0 end if cdCanvasFlush(cdcanvas) return IUP_DEFAULT end function IupOpen() canvas = IupCanvas(Icallback("redraw_cb"),"RASTERSIZE=600x400") dlg = IupDialog(canvas,`TITLE="Simple turtle graphics"`) IupMap(dlg) cdcanvas = cdCreateCanvas(CD_IUP, canvas) IupShow(dlg) IupSetAttribute(canvas, "RASTERSIZE", NULL) -- release the minimum limitation if platform()!=JS then IupMainLoop() IupClose() end if
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.