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 id (field ...) option ...)

field   =   id     |   [id #:mutable]           option   =   #:mutable     |   #:omit-constructor     |   #:omit-define-syntaxes     |   #:omit-define-values

For use with define-signature. The expansion of a struct signature form includes all of the identifiers that would be bound by (define-struct id (field ...) option ...), where the extra option #:omit-constructor omits the make-id identifier.

(struct/ctc id ([field contract-expr] ...) option ...)

field   =   id     |   [id #:mutable]           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.