6.7 Extending the Syntax of Signatures
(define-signature-form sig-form-id expr) (define-signature-form (sig-form-id id) body ...+)
Binds sig-form-id for use within a define-signature
form.
In the first form, the result of expr must be a transformer procedure. In the second form, sig-form-id is bound to a transformer procedure whose argument is id and whose body is the bodys. The result of the transformer must be a list of syntax objects, which are substituted for a use of sig-form-id in a define-signature expansion. (The result is a list so that the transformer can produce multiple declarations; define-signature has no splicing begin form.)
(struct/ctc id ([field contract-expr] ...) struct-option ...)
field = id | [id #:mutable] struct-option = #:mutable | #:omit-constructor | #:omit-define-syntaxes | #:omit-define-values
For use with define-signature. The struct/ctc form works
similarly to struct, but the constructor, predicate, field
accessors, and field mutators are contracted appropriately.