2021-11-24 07:43:12 -08:00

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Teliva - an environment for end-user programming

“Enable all people to modify the software they use in the course of using it.” —

“What if we, and all computer users, could reach in and modify our favorite apps?” —

“Software must be as easy to change as it is to use.” —

What's this, then?

An extremely naïve, brutalist attempt at packaging up simple Lua apps with almost all the stuff needed to edit and build them. You will need some Unix-like platform[1] with a C compiler and the ncurses and openssl libraries.

Here's how you run one of the example apps (the Tower of Hanoi):

git clone
cd teliva
make linux
src/teliva hanoi.tlv
screenshot of Teliva running the Towers of Hanoi

No matter what app you run, you are always guaranteed access to a single obvious, consistent way (currently the hotkey ctrl-e) to edit its sources. And to run the updates after editing. (video)

[1] Tested so far on Linux and Mac OSX; should also work on BSD, WSL on Windows, etc.

Isn't this just an IDE?

There's one big difference: these apps are not intended to be runnable outside of the Teliva environment. Editing the sources will always be a core feature that's front and center in the UI.

A second, more subtle difference: it's primarily an environment for running apps, and only secondarily for editing them. Starting up the environment puts you in a running app by default. Creating an app from a clean slate is a low-priority use case, as is lots of specialized support for developing complex apps. The sweet spot for Teliva is simple apps that people will want to edit after using for a while.

Why Lua?

It's reputedly the fastest interpreted language per line of implementation code.

Will it run any Lua program?

Not quite. My priority is providing a good experience for newcomers to comprehend and modify the programs they use. If it's not clear how to provide that experience for some kinds of Lua programs, I'd rather disable support for them in Teliva and let people use regular Lua. Or other platforms!

  • This approach doesn't make sense for batch programs, I think. I also don't yet have a good story for building server programs in this way.

  • I don't know how to obtain a simple, shallow graphics stack, so there's no support for graphics at the moment.

  • Teliva initializes the ncurses library by default, so apps should assume they have access to a (color, UTF-8) text-mode window for printing text to, and a keyboard for reading unbuffered keystrokes from.

  • Teliva doesn't use files for source code, so the require keyword no longer makes sense. You get some libraries preloaded (see below). Beyond those, apps should include all Lua code they want to use.

  • I want to provide sandboxed access to system resources (file system, network, etc.) which will likely create incompatibilities with the standard library. I'm disinclined to try to improve on Lua syntax, however. It's not my favorite, but it's good enough.

  • To create a well-behaved sandbox, Teliva doesn't support adding libraries with C bindings beyond the few it starts up with.

Teliva is not tested much at all yet. This is my first time programming either in Lua or within Lua. So bug reports are most appreciated if Lua programs behave unexpectedly under Teliva.

What's included?

  • Lua 5.1
  • The ncurses library for building text-mode user interfaces. (Alternative documentation)
  • The Kilo text editor, modified to use ncurses. (Read more about it in this fantastic walk-through.)
  • The lcurses binding for ncurses (as module curses).
  • The luasocket library of networking primitives (modules socket, http, url, headers, mime, ltn12).
  • The luasec library for HTTPS support (modules https and ssl).
  • The json.lua library for serializing/deserializing to JSON (module json).

The modules mentioned above are always available, just like standard Lua 5.1 libraries. They're available in their entirety with one exception:

While most things in these modules are currently available, I expect to delete capabilities throughout this stack as I discover features that don't fit well with the Teliva experience. If you find Teliva of use, please introduce yourself to me so that I am aware of your use cases. Anybody who is interested can gain a say in its future direction.

What's with the name?

Teliva is the Tamil root for clear. Very much aspirational.

Other apps to try out

  • Conway's Game of Life, as an example of an animated local app.

    src/teliva life.tlv


  • A viewer for LiChess TV, as an example of animation and accessing a remote API over a network.

    src/teliva chesstv.tlv



Most appreciated.