diff options
Diffstat (limited to 'guix/records.scm')
| -rw-r--r-- | guix/records.scm | 54 |
1 files changed, 50 insertions, 4 deletions
diff --git a/guix/records.scm b/guix/records.scm index 0649c90ea3..99507dc384 100644 --- a/guix/records.scm +++ b/guix/records.scm @@ -25,6 +25,8 @@ #:use-module (ice-9 regex) #:use-module (ice-9 rdelim) #:export (define-record-type* + this-record + alist->record object->fields recutils->alist @@ -93,6 +95,17 @@ interface\" (ABI) for TYPE is equal to COOKIE." (() #t))))))) +(define-syntax-parameter this-record + (lambda (s) + "Return the record being defined. This macro may only be used in the +context of the definition of a thunked field." + (syntax-case s () + (id + (identifier? #'id) + (syntax-violation 'this-record + "cannot be used outside of a record instantiation" + #'id))))) + (define-syntax make-syntactic-constructor (syntax-rules () "Make the syntactic constructor NAME for TYPE, that calls CTOR, and @@ -105,6 +118,7 @@ of TYPE matches the expansion-time ABI." ((_ type name ctor (expected ...) #:abi-cookie abi-cookie #:thunked thunked + #:this-identifier this-identifier #:delayed delayed #:innate innate #:defaults defaults) @@ -148,7 +162,14 @@ of TYPE matches the expansion-time ABI." (define (wrap-field-value f value) (cond ((thunked-field? f) - #`(lambda () #,value)) + #`(lambda (x) + (syntax-parameterize ((#,this-identifier + (lambda (s) + (syntax-case s () + (id + (identifier? #'id) + #'x))))) + #,value))) ((delayed-field? f) #`(delay #,value)) (else value))) @@ -234,6 +255,7 @@ may look like this: (define-record-type* <thing> thing make-thing thing? + this-thing (name thing-name (default \"chbouib\")) (port thing-port (default (current-output-port)) (thunked)) @@ -253,7 +275,8 @@ default value specified in the 'define-record-type*' form is used: The 'port' field is \"thunked\", meaning that calls like '(thing-port x)' will actually compute the field's value in the current dynamic extent, which is -useful when referring to fluids in a field's value. +useful when referring to fluids in a field's value. Furthermore, that thunk +can access the record it belongs to via the 'this-thing' identifier. A field can also be marked as \"delayed\" instead of \"thunked\", in which case its value is effectively wrapped in a (delay …) form. @@ -308,7 +331,7 @@ inherited." (with-syntax ((real-get (wrapped-field-accessor-name field))) #'(define-inlinable (get x) ;; The real value of that field is a thunk, so call it. - ((real-get x))))))) + ((real-get x) x)))))) (define (delayed-field-accessor-definition field) ;; Return the real accessor for FIELD, which is assumed to be a @@ -332,7 +355,9 @@ inherited." (syntax-case s () ((_ type syntactic-ctor ctor pred + this-identifier (field get properties ...) ...) + (identifier? #'this-identifier) (let* ((field-spec #'((field get properties ...) ...)) (thunked (filter-map thunked-field? field-spec)) (delayed (filter-map delayed-field? field-spec)) @@ -361,15 +386,36 @@ inherited." field-spec* ...) (define #,(current-abi-identifier #'type) #,cookie) + + #,@(if (free-identifier=? #'this-identifier #'this-record) + #'() + #'((define-syntax-parameter this-identifier + (lambda (s) + "Return the record being defined. This macro may +only be used in the context of the definition of a thunked field." + (syntax-case s () + (id + (identifier? #'id) + (syntax-violation 'this-identifier + "cannot be used outside \ +of a record instantiation" + #'id))))))) thunked-field-accessor ... delayed-field-accessor ... (make-syntactic-constructor type syntactic-ctor ctor (field ...) #:abi-cookie #,cookie #:thunked #,thunked + #:this-identifier #'this-identifier #:delayed #,delayed #:innate #,innate - #:defaults #,defaults)))))))) + #:defaults #,defaults))))) + ((_ type syntactic-ctor ctor pred + (field get properties ...) ...) + ;; When no 'this' identifier was specified, use 'this-record'. + #'(define-record-type* type syntactic-ctor ctor pred + this-record + (field get properties ...) ...))))) (define* (alist->record alist make keys #:optional (multiple-value-keys '())) |