Example bots for context-free languages

@infinite_scream Screams endlessly into the void.
- high-level description: This is the language of screams.
- formal description: Over the alphabet Σ = {A, H}, the language matches regular expression A⁺H⁺. Since it is regular and regular languages are a subset of context-free languages, it is context-free.
@not_regularLang
- high-level description: This is our canonical not-regular language, plus some frills to make it tweet in complete sentences.
- formal description: The alphabet is Σ = {0, 1}. The only rules are S → 0S1|ε.
- Tracery source code: here. Note that the rules have been expanded and some appear several times, to tweak the probability of following them, since Tracery picks one right-hand-side uniformly at random. Also, the basic grammar has been wrapped in a different starting rule, so that the bot produces tweets of the form: “String x is in some regular languages. It’s also in me!” where x = 0ⁿ1ⁿ for some n.
@autoflâneur Directions for getting lost.
- high-level description: Gives directions once an hour. If you follow these directions, you’ll definitely get lost.
- formal description: …? (think about it)
- Tracery source code: here
@SwarthmoreCS46
- high-level description: Automatically generates poll questions for CS46. (They are mostly answerable.)
- formal description: …?
- Tracery source code: (Secret. But I know that there is a problem with the un-escaped open-curly-bracket, and I don’t know how to fix it to display properly.)

You are free to use unicode characters or produce a language of strings that are something unusual. (Your language does not have to be words; see for example @EmojiAquarium and @softlandscapes below.) I encourage you to think creatively.

Here are some example bots for regular languages:

@foleyArtists Unconventional explanations for sound-effect production. (source)
@EmojiAquarium Emoji aquarium. (Similar to @tinylittlehomes and @thetinygallery.)
@lotsofeyes Lots of eyes. (source)
@HouseBudgets Automatically-generated plots for a house-hunting TV show.
@NerdGarbageBot Elevator pitches.
@trainsbotting Landscapes with trains driving through them.

Here are some example bots for context-free languages:

@thinkpiecebot Want to write a thinkpiece? Here’s a title.
@one_small_bot Fresh takes on Neil Armstrong’s famous quote.
@spacetravelbot Narrates your space adventure.
@contingencymsgs “Dictating to you Procedures to follow when Events occur.”
@softlandscapes Generates images of landscapes. (source – uses SVG syntax cleverly)
@midsomerplots Generates plots to a hypothetical, stereotypical British mystery TV show.

The Swarthmore students in Theory of Computation for spring 2019 came up with some cool ideas too:

The Lang Center for Bot “Wow! So much new construction on campus these days!”
@PokerMisery A bot that automates misery poker.
GoT Season 8 Spoilers for GoT season 8, only slightly accurate (this bot came out before GoT season 8 aired).
@NBA_HotTakesBot Hot and frankly bizarre takes on NBA news.
OracleBot1 Makes predictions for upcoming events. Sometimes far distant future ones.
Terrible Folktale Openings This bot can help with writer’s block for fairytales. But only at the beginning.
@upNextOnSwat Tells you one calendar update for Swarthmore. Not linked to reality AT ALL.
Meal Plan Gives a possible menu for the day’s meals. Not nutritionist-approved.