Debugging Turtles

Debugging Strategies

Read the Red Error

• Error message tells you which line number in the code is most likely to have the error.
• Error message gives you a hint about what is the cuase of the error.
• "attempt to call nil" error typically means calling a function that does not exist, usually a typo
• "'then' expected" Lua syntax error

Debugging Strategies (cont.)

Print Method to Troubleshoot Bad Logic

• Use print method to show the values of variables
• Use print method to show the order of code execution

Debugging Strategies (cont.)

Execute Small Blocks of Code

• Comment out code to execute small blocks to understand how the code functions
• Test each method to make sure it works as expected (note: smaller methods makes for easier testing and troubleshooting)

Load Buggy Code on Disk

1. Go to https://github.com/joedean/computercraft/tree/master/bugs
2. Download buggy_pool.lua and buggy_stairs.lua scripts
3. Open Minecraft and go to "Edit Profile" and click "Open Game Dir"
4. Keeping game dir open with file manager enter into existing world or create a new world in creative mode
5. Craft a disk drive and an advanced turtle next to the disk drive
6. Right click on turtle and 'cd' into disk directory
7. Create a file called "foo" add text and save
8. Go back to file manager and search for the "foo" file
9. typically "foo" would be in $GAMEDIR/saves/$WORLDNAME/computer/disk/1
10. Copy buggy_pool.lua and buggy_stairs.lua into same directory as FOO
11. Fix bugs in buggy_pool.lua first and then buggy_stairs.lua

Resources

• My email: joe.dean@gmail.com
• My Twitter: @joeddean
• Code: http://joedean.github.io/computercraft
• Slides: http://joedean.github.io/computercraft/presentations/maze.html

Thanks

• on-site.com: @onsitedotcom

Appendix I

Remove the need for Fueling a Turtle

Appendix II

Edit Program Outside of Minecraft