The article demonstrates a folklore Haskell trick to implement dependent if expressions—branches returning different types—without requiring actual dependent types. Using the RebindableSyntax extension and Church-encoded booleans, the technique redefines if-then-else to infer return types from branch contexts, working in any Hindley-Milner typed language.
Background
Dependent types allow values to influence types, enabling more precise type-level guarantees. This article explores how similar expressiveness can be approximated in languages with simpler type systems like Haskell using type inference tricks.
- Source
- Lobsters
- Published
- Sep 3, 2026 at 01:52 AM
- Score
- 5.0 / 10