Is Haskell a dependently-typed programming language?
The Glasgow Haskell Compiler (GHC) type-system extensions, such as Generalized Algebraic Datatypes (GADTs), multiparameter type classes and type families, give programmers the ability to encode domain-specific invariants in types. Clever functional programmers have used these features to enhance the reasoning capabilities of static type checking. But really, how far have we come?
In this talk, I will (attempt to) answer the question “Is it Dependent Types Yet?”, through examples, analysis and comparisons with modern full-spectrum dependently-typed languages, such as Agda and Coq. What sorts of dependently-typed programming can be done? What sorts of programming do these languages support that Haskell cannot? What should GHC learn from these languages, and conversely, what lessons can GHC offer in return?