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Learning Haskell from Scratch

A Brief Intro​

This is my attempt to organize my thoughts on Haskell as I learn it. But as someone who suffers from TL;DR syndrome, these docs are written with my own considerations in mind. A LOT can be skipped; most of the normal block text is just my own rationalization of how something works.

How to Use​

tip

If you're here to learn quickly or because you have ADHD as bad as mine, feel free to skip most of the fluff writing. The juicy parts are in callouts like this one, in the larger code blocks, lozenge tags that look like this: Rule and sometimes in the quotation blocks.

I'll hit on most topics in Haskell eventually (as I learn them and as they make sense to me), but not in the order of most typical programming courses/lessons.

I will also assume you know the basics of programming and are familiar with tools like REPLs and high-level concepts like "types" and "classes" (the latter of which, to be clear, isn't the same as a class in Java or JavaScript, but more like trait/impl in Rust or interfaces in Go and TypeScript)

warning

Remember, I'm new to Haskell, so not everything will be addressed adequately, if at all. I don't know squat at the moment.

Legend of Symbols​

Lozenge Tags​

The lozenges highlight specific moments in the text that I like to keep in mind.

Primary Tags​

  • Rule — A definition of how something works in Haskell.
  • Law — Same as a rule, but declared more forcefully, usually by multiple sources.
  • Maxim — A pithy reminder of a key point.
  • Note — A short elaboration or highlight of recent text.
  • Advanced — An advanced topic that is interesting, but won't be expanded upon, a.k.a, "an exercise left to the reader to figure out."

Admin Tags​

For my own use; if they show up on the site it's because I still haven't gotten to making the adjustment yet.

  • WIP — Something that is incomplete or needs confirmation regarding correctness.
  • Todo — Something I will follow up on later, in greater depth.

Command Line​

Some place in code blocks, I'll use λ to represent the REPL.

  • >λ    — the REPL prompt itself. Text that follows on the next is the explicit reply.
  • --λ  — a response from the REPL.

Which gets used depends on context and what is in focus for the lesson:

λ> 1 + 1
2

2 + 2
--λ  4