Скачать или смотреть Harold Carr- How to use Phantom Types and Existential Types in Production- λC 20 Global Edition

Code Examples: https://github.com/haroldcarr/using-p...

"Phantom types are a way to carry (possibly domain-specific) information in types.
Existential types are a way to hide information from places where those types are used.
This talk will develop a small application that:
parses and validates user input
uses phantom types to
turn validated data into types that carry ""proofs"" of that validation
call functions that require those proofs
uses existential types to
hide the state of pure computations from the IO layer that must pass that state
back into the pure layer later
ensure the app can only make valid state transitions (a.k.a., ""type-aligned sequences"")
By the end of the talk you should understand the often used phrases
""make illegal values unrepresentable"" -- via phantom types
""enforce abstraction boundaries in the type system"" -- via existential types"