Tortoise

Tortoise is a Logo interpreter for Ruby.

$ tortoise --png spec/data/complex.logo

Installation

Tortoise is available on rubygems.org. To install, add gem tortoise to your Gemfile or install manually with:

gem install tortoise

Usage

To use Tortoise, create an instance of Tortoise::Interpreter and execute any of the supported Logo commands.

# specify canvas size for this drawing
canvas_size = 11
interpreter = Tortoise::Interpreter.new(canvas_size)

# execute any supported commands
interpreter.pd
interpreter.setpos(1, 2)
interpreter.rt(90)
interpreter.fd(3)
interpreter.lt(45)
interpreter.bk(4)
interpreter.pu

Tortoise also accepts commands as an input string:

interpreter = Tortoise::Interpreter.new(11)
interpreter.draw "PD"
interpreter.draw "SETPOS 1 2"
interpreter.draw "RT 90"
interpreter.draw "FD 3"
interpreter.draw "LT 45"
interpreter.draw "BK 4"
interpreter.draw "PU"

You can execute entire blocks of commands at once:

interpreter = Tortoise::Interpreter.new(61)

interpreter.draw <<-STEPS
  RT 135
  FD 5
  REPEAT 2 [ RT 90 FD 15 ]
  RT 90
  FD 5
  RT 45
  FD 20
STEPS

Finally, commands can be executed when a Tortoise::Interpreter is instantiated. The command string must contain the canvas size in the first line. This is most useful when reading commands from a file. Assume we have the file drawing.logo:

61
RT 135
FD 5
REPEAT 2 [ RT 90 FD 15 ]
RT 90
FD 5
RT 45
FD 20

We can load and execute drawing.logo with:

file = File.new('drawing.logo')
tortoise = Tortoise::Interpreter.new(file.read)

Command Line Usage

Tortoise can be used on the command line to render logo command files. The output is rendered to standard out.

Usage: tortoise [OPTIONS] [FILE]

Options:
  --ascii   Render ascii output (default)
  --html    Render html output
  --png     Render png output

For example, if you'd like to render drawing.logo to drawing.txt as ascii:

$ tortoise drawing.logo > drawing.txt

Or as html:

$ tortoise --html drawing.logo > drawing.html

Or as png:

$ tortoise --png drawing.logo > drawing.png

Rendering The Canvas

Tortoise can currently render its canvas as ascii, html, or png.

interpreter = Tortoise::Interpreter.new(5)

interpreter.to_ascii  #=> return ascii
interpreter.to_html   #=> return html
interpreter.to_png    #=> return a png blob

Supported Commands

Tortoise only supports a small subset of all Logo commands.

PU: Lift the pen from the canvas
PD: Place the pen onto the canvas
RT x: Turn the tortoise x degrees to the right (increments of 45)
LT x: Turn the tortoise x degrees to the right (increments of 45)
FD x: Move the tortoise x steps forward
BK x: Move the tortoise x steps backward
SETPOS x y: Move the tortoise to position x, y (with pen up)
REPEAT n [ x ]: Repeat commands x a total of n times

tortoise