Archived tweet #11899 from the @leastfixedpoint Twitter Archive

@dabeaz @luskwater @fogus Yep! Racket has. And since about 2002 it has had higher-order contracts, which IIRC Eiffel never got. Racket's contracts are also a critical part of a major subfamily of the gradually-typed languages: they are automatically placed to guard typed/untyped boundaries.