Validus

Validators can be combined using ValidatorGroup or infix operators (<+>, >=>), enabling complex rules from simple parts, as shown in the email validator example.

Includes ready-to-use validators for strings, integers, dates, and collections with standard error messages, reducing boilerplate for common cases.

The applicative computation expression (validate { }) accumulates all validation errors across fields, not just the first, improving user feedback.

Facilitates creating domain-specific types like Email and E164 with private constructors and smart validators, enforcing invariants directly in the type system.