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records: Move 'make-syntactic-constructor' to the top level. 

* guix/records.scm (make-syntactic-constructor): New procedure, formerly
  nested in 'define-record-type*'.
This commit is contained in:
Ludovic Courtès 2015-01-19 22:30:55 +01:00
parent 9b543456d7
commit cf4efb394f
1 changed files with 89 additions and 93 deletions
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90
guix/records.scm
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@ -42,48 +42,11 @@
(format #f fmt args ...)
form))))
(define-syntax define-record-type*
(lambda (s)
"Define the given record type such that an additional \"syntactic
constructor\" is defined, which allows instances to be constructed with named
field initializers, à la SRFI-35, as well as default values. An example use
may look like this:
(define-record-type* <thing> thing make-thing
thing?
(name thing-name (default \"chbouib\"))
(port thing-port
(default (current-output-port)) (thunked)))
This example defines a macro 'thing' that can be used to instantiate records
of this type:
(thing
(name \"foo\")
(port (current-error-port)))
The value of 'name' or 'port' could as well be omitted, in which case the
default value specified in the 'define-record-type*' form is used:
(thing)
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.
It is possible to copy an object 'x' created with 'thing' like this:
(thing (inherit x) (name \"bar\"))
This expression returns a new object equal to 'x' except for its 'name'
field."
(define* (make-syntactic-constructor type name ctor fields
#:key thunked defaults)
"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."
"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."
(with-syntax ((type type)
(name name)
(ctor ctor)
@ -92,9 +55,8 @@ thunked fields."
#`(define-syntax name
(lambda (s)
(define (record-inheritance orig-record field+value)
;; Produce code that returns a record identical to
;; ORIG-RECORD, except that values for the FIELD+VALUE alist
;; prevail.
;; Produce code that returns a record identical to ORIG-RECORD,
;; except that values for the FIELD+VALUE alist prevail.
(define (field-inherited-value f)
(and=> (find (lambda (x)
(eq? f (car (syntax->datum x))))
@ -102,8 +64,7 @@ thunked fields."
car))
;; Make sure there are no unknown field names.
(let* ((fields (map (compose car syntax->datum)
field+value))
(let* ((fields (map (compose car syntax->datum) field+value))
(unexpected (lset-difference eq? fields 'expected)))
(when (pair? unexpected)
(record-error 'name s "extraneous field initializers ~a"
@ -149,8 +110,7 @@ thunked fields."
#'((field value) (... ...)))
car)
(let ((value
(car (assoc-ref dflt
(syntax->datum f)))))
(car (assoc-ref dflt (syntax->datum f)))))
(if (thunked-field? f)
#`(lambda () #,value)
value))))
@ -171,6 +131,42 @@ thunked fields."
(lset-difference eq? 'expected
fields))))))))))))
(define-syntax define-record-type*
(lambda (s)
"Define the given record type such that an additional \"syntactic
constructor\" is defined, which allows instances to be constructed with named
field initializers, à la SRFI-35, as well as default values. An example use
may look like this:
(define-record-type* <thing> thing make-thing
thing?
(name thing-name (default \"chbouib\"))
(port thing-port
(default (current-output-port)) (thunked)))
This example defines a macro 'thing' that can be used to instantiate records
of this type:
(thing
(name \"foo\")
(port (current-error-port)))
The value of 'name' or 'port' could as well be omitted, in which case the
default value specified in the 'define-record-type*' form is used:
(thing)
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.
It is possible to copy an object 'x' created with 'thing' like this:
(thing (inherit x) (name \"bar\"))
This expression returns a new object equal to 'x' except for its 'name'
field."
(define (field-default-value s)
(syntax-case s (default)
((field (default val) _ ...)