6.8. Class and instances declarations

This section documents GHC’s type-class extensions. There’s lots of background in the paper Type classes: exploring the design space (Simon Peyton Jones, Mark Jones, Erik Meijer).

• 6.8.1. Multi-parameter type classes
• 6.8.2. Undecidable (or recursive) superclasses
• 6.8.3. Constrained class method types
• 6.8.4. Default method signatures
• 6.8.5. Detailed requirements for default type signatures
• 6.8.6. Nullary type classes
• 6.8.7. Functional dependencies
• 6.8.8. Instance declarations and resolution