haskell-relude

Relude Conventions

Setup

Use cabal mixins for project-wide adoption (preferred over NoImplicitPrelude):

build-depends:    base >= 4.14 && < 5, relude >= 1.2 && < 1.3
mixins:           base hiding (Prelude)
                , relude (Relude as Prelude)
                , relude

Key Rules

• Text everywhere -- never use String except for legacy interop
• NonEmpty for non-empty collections -- use viaNonEmpty to safely bridge from lists
• readMaybe/readEither -- never read
• ordNub/hashNub -- never nub (O(n^2))
• Set.member/HashMap.member -- never elem on Set/HashSet (compile error in relude)
• whenM/unlessM -- for monadic conditionals
• one -- for singleton container construction
• Lifted IO -- use relude's lifted newIORef, readIORef, etc. directly (no liftIO wrapper needed)

Common Conversions

• encodeUtf8 / decodeUtf8 -- Text <-> ByteString
• toText / toLText / toString -- between string types
• toStrict / toLazy -- strict <-> lazy Text

Anti-patterns

• Using String when Text is available
• Using head/tail on [a] instead of NonEmpty or viaNonEmpty
• Using liftIO . readIORef instead of lifted readIORef
• Importing Prelude alongside Relude
• Leaving trace calls in production code

Reference

For migration guide and complete examples:

• references/relude-migration.md