A guided tour of Teliva
Teliva is an environment for running shareable little text-mode Lua apps that are easy to modify. This page is an in-progress guided tour through Teliva's Readme and Lua's reference documentation. We'll start out really slow and gradually accelerate.
You will need the following to build Teliva:
- A non-mobile computer running some sort of Unix variant. Teliva has been tested on Linux, OpenBSD and Mac OS X. (Other BSD variants and Windows Subsystem for Linux should require minor changes at most. Please contact me if you run into issues running Teliva on your computer.)
- A working C toolchain.
- Some fluency in typing commands at the terminal and interpreting their output.
If you have trouble with any of this, I'm always nearby and available to answer questions. The prerequisites are just things I haven't figured out how to explain yet. In particular, I want this page to be accessible to people who are in the process of learning programming, but I'm sure it isn't good enough yet for that. Ask me questions and help me improve it.
Task 1: running a Teliva app
Run the simplest example app:
Can you figure out what this app does, what you can do with it? There's a
number on screen. Hit
enter. The number increments by 1. Hit
x on your keyboard at the same time).
Run the app again. Try editing the app by hitting
ctrl-e. You see a "big
picture" view of the app. Spend a few moments scanning this page.
All programs consist of data and functions: code that operates on data in
some way. Teliva apps always start by running the special function
big picture orders functions from the top down. It shows
main up top,
main calls below, functions called by those functions next,
and so on.
Try browsing to some of the names visible on screen. Don't be afraid to experiment. The menu at the bottom always shows the hotkeys available to you at any point in time. Don't worry, everything you do can be undone.
Task 2: modifying a Teliva app
The first section of the Lua book starts with this one-line example:
Can you figure out where to add this line to the app's code so it's visible when the app runs?
Start by looking inside
main. Most Teliva apps tend to share a basic
- some initialization, followed by
- a loop that repeatedly:
- updates the screen, and then
- waits for the user to press a key
Can you map the lines of
main to this structure? Which function describes
how the app updates the screen?
- The function responsible for updating the screen is
renderbegins by clearing the screen (
After you make a change, can you figure out how to run your program?
Does it do what you expect? Feel free to edit your programs as often as
necessary. Programming is just long sessions of repeatedly editing (
and running (
ctrl-e) your program.
Once you're happy with your change, try exiting Teliva and restarting it with the same app. Do you still see your changes?
You could save the file
counter.tlv anywhere you like at this point. Or
share it with someone else. Everything needed for the app is in that file. If
you get stuck or have a question, send it to me!
Task 3: variables and arithmetic
Can you figure out how to modify this app to increment by 2 each time you
enter? Again, don't be afraid to experiment. The menu at the bottom
always shows the hotkeys available to you at any point in time. Don't worry,
everything you do can be undone.
Divide the problem into two parts in your head: where to make your change and
what change to make there. You've already gotten some practice selecting a
place to modify in Task 2. Repeat that process. Go back to the
What is the name of the variable (box containing a number) that decides what
number gets printed to screen? Go back to the big picture. Where is this
variable defined? How does it get modified when you press
(Buy the Lua book to support the creators of Lua. Teliva is a tiny molehill on the mountain of awesome that is Lua.)
- The function responsible for processing keystrokes is
- The variable that tracks what number to print on screen is