Plurrrr

Every day, around 40,000 thunderstorms crackle around the world, collectively turning Earth’s atmosphere into a giant electrical circuit. The upper reaches of the atmosphere have a positive charge, and the planet’s surface has a negative one. Even on sunny days with cloudless skies, the air carries a voltage of around 100 volts for every meter above the ground. In foggy or stormy conditions, that gradient might increase to tens of thousands of volts per meter.

Ballooning spiders operate within this planetary electric field. When their silk leaves their bodies, it typically picks up a negative charge. This repels the similar negative charges on the surfaces on which the spiders sit, creating enough force to lift them into the air. And spiders can increase those forces by climbing onto twigs, leaves, or blades of grass. Plants, being earthed, have the same negative charge as the ground that they grow upon, but they protrude into the positively charged air. This creates substantial electric fields between the air around them and the tips of their leaves and branches—and the spiders ballooning from those tips.

Today, I want to explore Parsec, and most specifically how Parsec works. Parsing is ubiquitous, and most Haskell programs will use Parsec or one of its variants (megaparsec or attoparsec). While it’s possible to use those libraries without caring about how they work, I think it’s fascinating to develop a mental model for their inner design; namely, monadic parser combinators, as it is a simple and elegant technique that is useful beyond the use case of parsing raw text. At Hasura, we have recently used this technique to rewrite the code that generates a GraphQL schema and checks an incoming GraphQL query against it.

It was only when I recently heard someone else say, “git stash is scary” that I realized it was top of my list of fears too. It just usually feels like there’s a chance I’ll just lose all of my in progress work to the depths of stashes and never be able to get the right incantation of git commands to reincarnate my code.