The subsequent bindings were added by Asumu Takikawa.
Creates a contract that acts like contract but will also accept #f. Intended to describe situations where a failure or default value may be used.
The subsequent bindings were added by Carl Eastlund <firstname.lastname@example.org>.
This contract recognizes Racket truth values, i.e., any value, but with a more informative name and description. Use it in negative positions for arguments that accept arbitrary truth values that may not be booleans.
The subsequent bindings were added by Neil Toronto <email@example.com>.
Identifies values that meet the contract elem-contract, lists of such values, lists of lists, and so on.