On Thu, 2009-12-24 at 05:31 -0600, Eduardo Cavazos wrote:
> Something I use heavily in the 'box2d-lite' code is a
> 'define-record-type++' macro:
>
> http://github.com/dharmatech/box2d-lite/blob/master/util/define-record-type.sls
>
> It expands into a call to the full 'define-record-type' along with some
> additional definitions.
>
> However, it's cheesy in that it only supports a subset of the syntax of
> the full 'define-record-type', along with some additional syntax.
>
> Is there a pure R6RS definition of the 'define-record-type' macro
> available somewhere? The definitions I found had implementation specific
> code in them.
>
> I'd rather base my 'define-record-type' deriviative on a full version.
> I.e. start with the full definition and throw in my extensions.
You don't need to go that far. Just extract what you need and pass
everything else through:
(define-syntax define-record-type++
(lambda (stx)
(syntax-case stx ()
((_ name-spec is-type import-type rest ...)
;; Invalid name-spec will be detected by define-record-type.
;; Invalid is-type or import-type should be detected by
;; define-is-type-syntax or define-import-type-syntax.
;; Invalid rest will be detected by define-record-type.
(let loop ((r (syntax (rest ...)))
(f #F)
(m #F)
(a (quote ())))
(if (null? r)
(if (and f m)
(with-syntax (((field-name ...) f)
(methods m)
((DRT-clauses ...) (reverse a))
(type-name (syntax-case (syntax name-spec) ()
((x . _) (syntax x))
(_ (syntax name-spec)))))
(syntax
(begin
(define-record-type name-spec
DRT-clauses ...)
(define-is-type-syntax is-type
type-name
(fields field-name ...)
methods)
(define-import-type-syntax import-type
type-name
(fields field-name ...)
methods))))
(syntax-violation #F "missing fields and/or methods" stx #F))
(syntax-case (car r) (fields methods)
((fields x ...)
;; Multiple fields clauses will be detected by define-record-type.
(loop (cdr r)
(map (lambda (x)
(syntax-case x ()
((_ name . _) (syntax name))
(_ x)))
(syntax (x ...)))
m
(cons (car r) a)))
((methods . _)
;; Invalid methods sub-clauses should be detected by
;; define-is-type-syntax and/or define-import-type-syntax.
(if m
(syntax-violation #F "multiple methods clauses" stx #F)
(loop (cdr r) f (car r) a)))
(_
(loop (cdr r) f m (cons (car r) a))))))))))
I tested that this works:
(define-record-type++ (foo foo-maker is-it-a-foo?)
is-foo import-foo
(fields a (mutable b) (immutable c c-get))
(methods)
(sealed #T))
--
: Derick
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