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:
Perl
<lang perl>#!/usr/bin/perl
use strict; # https://rosettacode.org/wiki/Simple_turtle_graphics use warnings; use Tk; use List::Util qw( max );
my $radian = 180 / atan2 0, -1; sub dsin { sin $_[0] / $radian } sub dcos { cos $_[0] / $radian }
my $mw = MainWindow->new; my $c = $mw->Canvas(
-width => 900, -height => 900, )->pack;
$mw->Button(-text => 'Exit', -command => sub {$mw->destroy},
)->pack(-fill => 'x');
my $pen = 1; # true for pendown, false for penup my @location = (0, 0); # upper left corner my $direction = 0; # 0 for East, increasing clockwise
$mw->after(0, \&run); MainLoop; -M $0 < 0 and exec $0;
my @stack; sub save { push @stack, [ $direction, @location ] } sub restore { ($direction, @location) = @{ pop @stack } } sub turn { $direction += shift } sub right { turn shift } sub left { turn -shift } sub forward
{ my $x = $location[0] + $_[0] * dcos $direction; my $y = $location[1] + $_[0] * dsin $direction; $pen and $c->createLine( @location, $x, $y, -width => 3 ); @location = ($x, $y); }
sub back { turn 180; forward shift; turn 180 } sub penup { $pen = 0 } sub pendown { $pen = 1 }
sub text
{ $c->createText( @location, -text => shift ) }
sub box
{ my ($w, $h) = @_; for (1 .. 2) { forward $w; left 90; forward $h; left 90; } }
sub house
{ my $size = shift; box $size, $size; right 90; for ( 1 .. 3 ) { right 120; forward $size; } penup; left 90; forward $size; left 90; save; forward $size * 1 / 4; pendown; box $size / 4, $size / 2; penup; restore; }
sub graph
{ save; my $size = shift; my $width = $size / @_; my $hscale = $size / max @_; for ( @_ ) { box $width, $hscale * $_; save; penup; forward $width / 2; left 90; forward 10; text $_; pendown; restore; forward $width; } restore; }
sub run
{ penup; forward 50; right 90; forward 400; pendown; house(300); penup; forward 400; pendown; graph( 400, 2,7,4,5,1,8,6 ); }</lang>
Phix
You can run this online here.
-- -- 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.