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authorLudovic Courtès <ludo@gnu.org>2015-01-19 23:21:47 +0100
committerLudovic Courtès <ludo@gnu.org>2015-01-19 23:30:42 +0100
commit310b32a2a6136a99d3c48542bf68d0d8b550f42f (patch)
treeb2683034739ef7ef05b15839557ae6c22d894843 /guix/records.scm
parent0db40ed289388d049ec9ecfd9661cc1d74a9ef3e (diff)
records: Add support for delayed fields.
* guix/records.scm (make-syntactic-constructor): Add #:delayed parameter. [delayed-field?]: New procedure. [wrap-field-value]: Use it. (define-record-type*)[delayed-field?, wrapped-field?]: New procedures. [thunked-field-accessor-name]: Rename to... [wrapped-field-accessor-name]: ... this. [field-spec->srfi-9]: Change 'thunked' to 'wrapped'. [delayed-field-accessor-definition]: New procedure. Compute delayed-field accessors and emit them. Pass #:delayed to 'make-syntactic-constructor'. * tests/records.scm ("define-record-type* & delayed", "define-record-type* & delayed & default", "define-record-type* & delayed & inherited"): New tests.
Diffstat (limited to 'guix/records.scm')
-rw-r--r--guix/records.scm63
1 files changed, 52 insertions, 11 deletions
diff --git a/guix/records.scm b/guix/records.scm
index 8a4d6a7bb6..fd17e135e1 100644
--- a/guix/records.scm
+++ b/guix/records.scm
@@ -43,10 +43,12 @@
form))))
(define* (make-syntactic-constructor type name ctor fields
- #:key (thunked '()) (defaults '()))
+ #:key (thunked '()) (defaults '())
+ (delayed '()))
"Make the syntactic constructor NAME for TYPE, that calls CTOR, and expects
all of FIELDS to be initialized. DEFAULTS is the list of FIELD/DEFAULT-VALUE
-tuples, and THUNKED is the list of identifiers of thunked fields."
+tuples, THUNKED is the list of identifiers of thunked fields, and DELAYED is
+the list of identifiers of delayed fields."
(with-syntax ((type type)
(name name)
(ctor ctor)
@@ -81,10 +83,15 @@ tuples, and THUNKED is the list of identifiers of thunked fields."
(define (thunked-field? f)
(memq (syntax->datum f) '#,thunked))
+ (define (delayed-field? f)
+ (memq (syntax->datum f) '#,delayed))
+
(define (wrap-field-value f value)
- (if (thunked-field? f)
- #`(lambda () #,value)
- value))
+ (cond ((thunked-field? f)
+ #`(lambda () #,value))
+ ((delayed-field? f)
+ #`(delay #,value))
+ (else value)))
(define (field-bindings field+value)
;; Return field to value bindings, for use in 'let*' below.
@@ -161,6 +168,9 @@ 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.
+A field can also be marked as \"delayed\" instead of \"thunked\", in which
+case its value is effectively wrapped in a (delay …) form.
+
It is possible to copy an object 'x' created with 'thing' like this:
(thing (inherit x) (name \"bar\"))
@@ -176,6 +186,15 @@ field."
(field-default-value #'(field options ...)))
(_ #f)))
+ (define (delayed-field? s)
+ ;; Return the field name if the field defined by S is delayed.
+ (syntax-case s (delayed)
+ ((field (delayed) _ ...)
+ #'field)
+ ((field _ options ...)
+ (delayed-field? #'(field options ...)))
+ (_ #f)))
+
(define (thunked-field? s)
;; Return the field name if the field defined by S is thunked.
(syntax-case s (thunked)
@@ -185,9 +204,12 @@ field."
(thunked-field? #'(field options ...)))
(_ #f)))
- (define (thunked-field-accessor-name field)
+ (define (wrapped-field? s)
+ (or (thunked-field? s) (delayed-field? s)))
+
+ (define (wrapped-field-accessor-name field)
;; Return the name (an unhygienic syntax object) of the "real"
- ;; getter for field, which is assumed to be a thunked field.
+ ;; getter for field, which is assumed to be a wrapped field.
(syntax-case field ()
((field get options ...)
(let* ((getter (syntax->datum #'get))
@@ -200,8 +222,8 @@ field."
(syntax-case field ()
((name get options ...)
#`(name
- #,(if (thunked-field? field)
- (thunked-field-accessor-name field)
+ #,(if (wrapped-field? field)
+ (wrapped-field-accessor-name field)
#'get)))))
(define (thunked-field-accessor-definition field)
@@ -209,16 +231,27 @@ field."
;; thunked field.
(syntax-case field ()
((name get _ ...)
- (with-syntax ((real-get (thunked-field-accessor-name field)))
+ (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)))))))
+ (define (delayed-field-accessor-definition field)
+ ;; Return the real accessor for FIELD, which is assumed to be a
+ ;; delayed field.
+ (syntax-case field ()
+ ((name get _ ...)
+ (with-syntax ((real-get (wrapped-field-accessor-name field)))
+ #'(define-inlinable (get x)
+ ;; The real value of that field is a promise, so force it.
+ (force (real-get x)))))))
+
(syntax-case s ()
((_ type syntactic-ctor ctor pred
(field get options ...) ...)
(let* ((field-spec #'((field get options ...) ...))
(thunked (filter-map thunked-field? field-spec))
+ (delayed (filter-map delayed-field? field-spec))
(defaults (filter-map field-default-value
#'((field options ...) ...))))
(with-syntax (((field-spec* ...)
@@ -228,16 +261,24 @@ field."
(and (thunked-field? field)
(thunked-field-accessor-definition
field)))
+ field-spec))
+ ((delayed-field-accessor ...)
+ (filter-map (lambda (field)
+ (and (delayed-field? field)
+ (delayed-field-accessor-definition
+ field)))
field-spec)))
#`(begin
(define-record-type type
(ctor field ...)
pred
field-spec* ...)
- (begin thunked-field-accessor ...)
+ (begin thunked-field-accessor ...
+ delayed-field-accessor ...)
#,(make-syntactic-constructor #'type #'syntactic-ctor #'ctor
#'(field ...)
#:thunked thunked
+ #:delayed delayed
#:defaults defaults))))))))
(define* (alist->record alist make keys