2.8 Struct Descriptors

7.7

2.8 Struct Descriptors

procedure
(struct-descriptor? v) → boolean?
v : any/c

A predicate for structure type descriptors, initialized or uninitialized.

procedure
(initialized-struct-descriptor? v) → boolean?
v : any/c

A predicate for initialized structure type descriptors, as returned by the make-struct-implementation function. Implies struct-descriptor?.

procedure
(uninitialized-struct-descriptor? v) → boolean?
v : any/c

A predicate for uninitialized structure type descriptors, as passed to the prop-maker argument of make-struct-implementation. An uninitialized descriptor’s constructor, predicate, accessor, and mutator functions must not be called until the structure type is created — that is, until the corresponding call to make-struct-implementation returns.

procedure
(struct-descriptor-type descriptor) → struct-type?
descriptor : initialized-struct-descriptor?

Returns the raw struct-type? instance in descriptor, which must be initialized. Uninitialized structure type descriptors do not yet have an associated struct-type? instance.

procedure
(struct-descriptor-super-type descriptor)
→ (or/c struct-info? #f)
  descriptor : struct-descriptor?
procedure
(struct-descriptor-name descriptor) → symbol?
  descriptor : struct-descriptor?
procedure
(struct-descriptor-mutable-fields descriptor) → natural?
  descriptor : struct-descriptor?
procedure
(struct-descriptor-immutable-fields descriptor) → natural?
  descriptor : struct-descriptor?
procedure
(struct-descriptor-auto-fields descriptor) → natural?
  descriptor : struct-descriptor?
procedure
(struct-descriptor-constructor descriptor) → procedure?
  descriptor : struct-descriptor?
procedure
(struct-descriptor-predicate descriptor) → (-> any/c boolean?)
  descriptor : struct-descriptor?
procedure
(struct-descriptor-accessor descriptor)
→ (-> any/c natural? any/c)
  descriptor : struct-descriptor?
procedure
(struct-descriptor-mutator descriptor)
→ (-> any/c natural? any/c void?)
  descriptor : struct-descriptor?

Accessors for the various fields of a structure type descriptor.

procedure
(make-struct-implementation
#:name name
[ #:mutable-fields mutable-fields
#:immutable-fields immutable-fields
#:auto-fields auto-fields
#:auto-field-value auto-value
#:super-type super-type
#:property-maker prop-maker
#:inspector inspector
#:guard guard
#:constructor-name constructor-name])
→ initialized-struct-descriptor?
  name : symbol?
  mutable-fields : natural? = 0
  immutable-fields : natural? = 0
  auto-fields : natural? = 0
  auto-value : any/c = #f
  super-type : (or/c struct-type? #f) = #f
   prop-maker :
(-> uninitialized-struct-descriptor?
    (listof (cons/c struct-type-property? any/c)))
= (λ (_) empty)
  inspector : (or/c inspector? 'prefab #f) = (current-inspector)
  guard : (or/c procedure? #f) = #f
  constructor-name : (or/c symbol? #f) = #f

Like make-struct-type, but with keyword arguments instead of positional arguments and returning a single struct-descriptor? value instead of multiple values. Additional differences include:

Instead of fields defaulting to mutable and specifying a list of indices for immutable fields, this function accepts separate arguments for the number of mutable fields and the number of immutable fields. The created struct type puts all mutable fields before all immutable fields.
Structure type properties are created by the prop-maker function, which is called with the descriptor before it is initialized. This allows property values to refer to the functions associated with the descriptor, without requiring users of make-struct-implementation to create mutually recursive definitions.
The proc-spec argument is not supported directly. This argument is made obsolete by prop:procedure; instead of passing proc-spec callers should include a value for prop:procedure in the result of prop-maker.

Examples:

> (define point-descriptor
(make-struct-implementation #:name 'point #:immutable-fields 2))
> (define point (struct-descriptor-constructor point-descriptor))
> (point 1 2)
#<point>

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2.1	Interfaces Common to All Types
2.2	Record Types
2.3	Tuple Types
2.4	Enum Types
2.5	Singleton Types
2.6	Wrapper Types
2.7	Object Types
2.8	Struct Descriptors