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Documented the new argument order accepted by define-generics.

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This commit is contained in:
Carl Eastlund 2013-07-08 01:32:48 -04:00
parent 065622d64b
commit b9f2e4d541
1 changed files with 16 additions and 12 deletions
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28
pkgs/racket-pkgs/racket-doc/scribblings/reference/generic.scrbl
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@ -16,21 +16,20 @@ using a @racket[define-generics] form. Method implementations for
a structure type are defined using the @racket[#:methods] keyword a structure type are defined using the @racket[#:methods] keyword
(see @secref["define-struct"]). (see @secref["define-struct"]).
@defform/subs[(define-generics id [#:defined-table defined-table-id] @defform/subs[(define-generics id
[method-id . kw-formals*] generics-opt ...
... [method-id . kw-formals*] ...
maybe-defaults) generics-opt ...)
([kw-formals* (arg* ...) ([generics-opt
(code:line #:defined-table defined-table-id)
(code:line #:defaults ([pred? method-impl ...] ...))]
[kw-formals* (arg* ...)
(arg* ...+ . rest-id) (arg* ...+ . rest-id)
rest-id] rest-id]
[arg* arg-id [arg* arg-id
[arg-id] [arg-id]
(code:line keyword arg-id) (code:line keyword arg-id)
(code:line keyword [arg-id])] (code:line keyword [arg-id])])]{
[maybe-defaults (code:line)
(code:line #:defaults ([pred?
method-impl ...]
...))])]{
Defines Defines
@ -59,7 +58,11 @@ by-position argument that is @racket[free-identifier=?] to
@racket[id]. That argument is used in the generic definition to @racket[id]. That argument is used in the generic definition to
locate the specialization. locate the specialization.
When @racket[defined-table-id] is provided, it is defined as a Keyword options to @racket[define-generics] may be provided both before and
after the list of methods, but not in the middle.
The @racket[#:defined-table] option may be provided at most once.
When it is provided, @racket[defined-table-id] is defined as a
procedure that takes an instance of the generics and returns an procedure that takes an instance of the generics and returns an
immutable @tech{hash table} that maps symbols corresponding to method immutable @tech{hash table} that maps symbols corresponding to method
names to booleans representing whether or not that method is names to booleans representing whether or not that method is
@ -67,7 +70,8 @@ implemented by the instance. This table is intended for use by
higher-level APIs to adapt their behavior depending on method higher-level APIs to adapt their behavior depending on method
availability. availability.
When @racket[maybe-defaults] is provided, each generic function The @racket[#:defaults] option may be provided at most once.
When it is provided, each generic function
uses @racket[pred?]s to dispatch to the given default implementations, uses @racket[pred?]s to dispatch to the given default implementations,
@racket[method-impl]s, if dispatching to the generic method table fails. @racket[method-impl]s, if dispatching to the generic method table fails.
The syntax of the @racket[method-impl]s is the same as the methods The syntax of the @racket[method-impl]s is the same as the methods