2020 UPDATE: Due to tk being removed from the Ruby standard library and due to changes on macOS (which I primarily use), this library is no longer as easy to use for beginners as it once was. If you can come up with solutions to resolve this issue, I am all ears.

2021 UPDATE: I have not had to time to spend updating this project but some kind people in the issue tracker have suggestions on installing Tk in the modern age. See #5 (comment)

gem install trtl

Trtl is a simple 'turtle' system inspired by Python's turtle.py. It provides simple turtle drawing capabilities in Ruby, even if you're just at an IRB prompt. It leans on Tk (which used to be in Ruby's standard library but is now an external gem).

If Trtl detects you're in an IRb or Pry session, it'll automatically make turtle methods available directly at the prompt. For example:

$ irb
> require 'trtl'
> forward 100
# At this point, a window appears with the turtle

If you wish to use Trtl from a regular Ruby script, you have a few options. You can create a Trtl instance and use it directly:

require 'trtl'
t = Trtl.new
10.times { t.left(24); t.forward(30); t.ensure_drawn }
t.wait

You can use Trtl's run method to use it in a more interactive fashion:

Trtl.new.run { 10.times { left(24); forward(30); ensure_drawn } }

Or you can include InteractiveTurtle and get a similar effect as if you were in IRb:

include InteractiveTurtle
10.times { left(24); forward(30) }

Note: Using InteractiveTurtle makes drawing slower as it ensures all graphics are drawn after every action (as necessary for IRb use).

Only a small number of commands are currently implemented, but they're enough for the major actions:

• title(title_name)
• forward(distance) - aliased as fd
• back(distance) - aliased as bk and backward
• left(angle) - aliased as lt
• right(angle) - aliased as rt
• pen_up - aliased as pu and up and penup
• pen_down - aliased as pd and down and pendown
• color(color_name) - aliased as pencolor
• move(x, y) - aliased as goto
• position - aliased as pos
• circle(radius, extent = 360, steps = 360)
• dot(size) - draws a dot, defaults to a sensible size but you can supply if you want
• is_drawing?
• width(width_in_pixels)

The examples in the examples folder should be reasonably illustrative. If you try any of them, try example4.rb - it renders an awesome looking tree.

• turtle.py for inspiration (in the 'Ruby needs this!' sense)
• Some of the examples taken from examples for an earlier Ruby turtle found at http://www.rubyquiz.com/quiz104.html

Copyright (c) 2012-2017 Peter Cooper (other than minor parts of some samples.)

MIT licensed. See LICENSE.md

  graph TD;
      A-->B;
      A-->C;
      B-->D;
      C-->D;