Clogo is a LOGO REPL (interpreter) written in Clojure. It can control a Lego NXT2 turtle robot or be used in standalone mode.

Logo is an education programming language, designed in 1967 … remembered mainly for its use of “turtle graphics” … Logo is a multi-paradigm adaptation and dialect of Lisp — Wikipedia Logo (programming language)

WTF? (What’s This For?)

  • For kids to learn programming, through the good old Logo turtle
  • To mess up with Clojure, with many side effects (such as drawing on the screen and even commanding a robot)
  • To play with Lego Mindstorms and build a “turtle robot” which holds a pencil to draw on paper

Quick Start (without the Lego Mindstorms robot)

You can try Clogo very easily. Even if you don’t have Lego Mindstorms, you can learn the LOGO language and command the turtle to draw on the screen. All you need is either leiningen or maven to build the app.

git clone

  • With leiningen: lein compile lein uberjar java -jar target/clogo-0.1.0-SNAPSHOT-standalone.jar
  • With maven: mvn install java -jar target/clogo-0.1.0-SNAPSHOT-jar-with-dependencies.jar

See the cLOGO Crash Course to find out what you can do with Clogo

Instructions for building Clogo to control a Lego NXT2 turtle robot

If you plan to try with a Lego NXT2 robot, you will need

  • Maven
  • Lejos NXJ (Java for LEGO Mindstorms)
  • Bluecove (bluetooth library to connect to the turtle robot)

Note: I am on Mac OSX and haven’t tested on other platforms.

Here are the steps to follow:

  1. Download Lejos libraries: get leJOS_NXJ_0.9.1beta-3.tar.gz from
  2. Install them in your local Maven repo:
    mvn install:install-file -Dfile=leJOS_NXJ_0.9.1beta-3/lib/pc/pccomm.jar -DgroupId=lejos.pc -DartifactId=pccomm -Dversion=0.9.1-beta3 -Dpackaging=jar
    mvn install:install-file -Dfile=leJOS_NXJ_0.9.1beta-3/lib/nxt/classes.jar -DgroupId=lejos.nxt -DartifactId=classes -Dversion=0.9.1-beta3 -Dpackaging=jar
  3. Install and build bluecove (2.1.1-SNAPSHOT) git clone mvn install
  4. Use Maven to build the LOGO interpreter and the LogoTurtle software to be downloaded onto the NXT2 robot. You need to specify the path of leJOS, because the compiler will be required to compile the turtle code.
    mvn install -Pnxt -Dnxj.home=/Users/yourhome/leJOS_NXJ_0.9.1beta-3
  5. Build your turtle robot. It will use 2 motors to move and turn, and one motor to control the pencil. Once the robot is built, you should configure bluetooth and pair your NXT2 processor with your computer.
  6. Download the LogoTurtle.nxd / LogoTurtle.nxj onto your NXT2 processor (using the USB link shipped with your Lego Mindstorms); then start your robot. It will show the letters “connecting…” on its LCD screen.
  7. Start the application on your computer.
    java -jar target/clogo-0.1.0-SNAPSHOT-jar-with-dependencies.jar
    Within a few seconds, the application should try to connect with the turtle using bluetooth. Each command to the LOGO REPL will be sent to the robot for execution.


cLOGO Crash Course

First of all, note that this LOGO interpreter only understand French LOGO commands (although it should be straighforward to support other languages -contributions are welcome!)

Here are some commands you can use:

Basic drawing commands

  1. AVANCE X (resp RECULE X) : move forward (resp backward) for X steps
  2. GAUCHE Y (resp DROITE X) : make a left (resp right) turn of X degrees
  3. LEVECRAYON (resp BAISSECRAYON) : put the pen down (resp up)
  4. MONTRETORTUE (resp CACHETORTUE) : show (resp hide) the turtle

Programming constructs

  1. REPETE N [ ... ] : repeat N times the instructions in square brackets
  2. POUR PROCNAME ... FIN : defines a procedure called PROCNAME which can be reused by writing its name. You can also pass parameters to the procedure like POUR PROCNAME :PARAM1 ... FIN where :PARAM1 is an input parameter of the procedure which can then be used by writing PARAM1 (without the “:” prefix).
  3. DONNE VARNAME VALUE : defines a variable VARNAME with a certain VALUE which can be an expression.


  1. Clogo supports both prefix and infix operatorsr:
    • Infix operators: X + YX - YX * Y and X / Y.
  2. You can also use parentheses in your expressions

Writing to the screen

  1. ECRIS X : write the value of X to the screen
  2. Clogo has 2 predefined variables:
    • POS : the position of the turtle (x and y)
    • CAP : the orientation of the turtle (in degrees)


  • Draw a square
    DROITE 90
  • Draw a circle (actually a 36-sides polygon)
    REPETE 36 [ AVANCE 1 DROITE 10 ]


Clogo was an experiment / personal project to get my children play with Lego Mindstorms and learn programming through the LOGO language. It has only been tested on Mac (OSX Lion-Mavericks) and the turtle robot was an original creation (which also required some non-NXT bricks).

Feel free to try and contribute if you like Clogo.

Spreading the word by posting on Twitter or blogging about Clogo is also a great way to show your appreciation.


Copyright © 2014 Antoine Choppin

Distributed under the Eclipse Public License, the same as Clojure.