My favorite is the Hindley-Milner type system algorithm: https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_system#Towards_an_algorithm https://en.wikipe

My favorite is the Hindley-Milner type system algorithm: https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_system#Towards_an_algorithm https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_sy... It is what is used in ML based languages to infer type and apparently Haskell uses it a bit too