eopl

Essentials of Programming Languages in Haskell

This repository shows my long-term learning of Haskell and interpreters of programming languages, wish I can finish the whole book!

My likes & dislikes

Likes

1. Reader Monad: elegant, safe to use

Dislikes

1. State Monad: ugly, prone to memory leak, and if you need to mimic mutable by State, perhaps you need to just use mutable references.

Formatting

To check if files are already formatted (useful on CI):

$ fourmolu --mode check .

Find all the source files in a project with git ls-files and then use fourmulu to format those files:

$ fourmolu --mode inplace $(git ls-files '*.hs')
# Or to avoid hitting command line length limits and enable parallelism (12-way here):
$ git ls-files -z '*.hs' | xargs -P 12 -0 fourmolu --mode inplace

Acknowledgements

• Thanks That One Cool Reader Trick, which teaches me the cool trick!

• Thanks About that Reader trick, which teaches me the disadvantage of the Reader.

• Thanks Lecture_EOPL, which reminds me to get started on my project and as my reference.