Haskell Development

# Haskell Project

This is a Haskell project using GHC and Cabal/Stack.

## Project Structure
- `app/Main.hs` - Application entry point
- `src/` - Library source modules
- `test/` - Test suites
- `bench/` - Benchmarks
- `*.cabal` or `package.yaml` - Package definition

## Code Style
- Follow the Haskell Style Guide
- Use explicit export lists for all modules
- Prefer qualified imports for clarity
- Use hlint suggestions unless they reduce readability
- Keep functions small and composable
- Write type signatures for all top-level definitions

## Type System
- Leverage the type system to eliminate invalid states
- Use newtypes for domain types instead of raw primitives
- Prefer sum types (ADTs) for modeling alternatives
- Use phantom types or GADTs when extra type safety is needed
- Avoid partial functions (head, tail, fromJust) — use safe alternatives

## Error Handling
- Use Either for recoverable errors with typed error values
- Use ExceptT for monadic error handling
- Avoid exceptions for control flow — reserve for truly exceptional cases
- Provide descriptive error types, not just strings

## Performance
- Use strict fields in data types where appropriate
- Profile before optimizing — use +RTS -p
- Prefer Text over String for text processing
- Use ByteString for binary data
- Be mindful of lazy evaluation and space leaks

## Testing
- Use Hspec for unit and integration tests
- Use QuickCheck for property-based testing
- Test pure functions exhaustively — they're easy to test
- Use tasty as the test framework runner

## Commands
- `cabal build` - Build the project
- `cabal run` - Run the application
- `cabal test` - Run all tests
- `cabal repl` - Start interactive REPL
- `hlint src/` - Run linter
- `fourmolu -i src/` - Format source code
- `ghcid` - Fast type-checking on file changes