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Version: 5.0.2

25 Structs

Ryan Culpepper <ryanc@racket-lang.org>

 (require unstable/struct)

This library is unstable; compatibility will not be maintained. See Unstable for more information.

(make struct-id expr ...)
Creates an instance of struct-id, which must be bound as a struct name. The number of exprs is statically checked against the number of fields associated with struct-id. If they are different, or if the number of fields is not known, an error is raised at compile time.


  > (define-struct triple (a b c))
  > (make triple 3 4 5)


  > (make triple 2 4)

  eval:4:0: make: wrong number of arguments for struct triple

  (expected 3, got 2) in: (make triple 2 4)

(struct->list v [#:on-opaque on-opaque])  (or/c list? #f)
  v : any/c
  on-opaque : (or/c 'error 'return-false 'skip) = 'error
Returns a list containing the struct instance v’s fields. Unlike struct->vector, the struct name itself is not included.

If any fields of v are inaccessible via the current inspector the behavior of struct->list is determined by on-opaque. If on-opaque is 'error (the default), an error is raised. If it is 'return-false, struct->list returns #f. If it is 'skip, the inaccessible fields are omitted from the list.


  > (define-struct open (u v) #:transparent)
  > (struct->list (make-open 'a 'b))

  '(a b)

  > (struct->list #s(pre 1 2 3))

  '(1 2 3)

  > (define-struct (secret open) (x y))
  > (struct->list (make-secret 0 1 17 22))

  struct->list: expected argument of type <non-opaque

  struct>; given (secret 0 1 ...)

  > (struct->list (make-secret 0 1 17 22) #:on-opaque 'return-false)


  > (struct->list (make-secret 0 1 17 22) #:on-opaque 'skip)

  '(0 1)

  > (struct->list 'not-a-struct #:on-opaque 'return-false)


  > (struct->list 'not-a-struct #:on-opaque 'skip)