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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*'.
master
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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182
guix/records.scm
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@ -42,6 +42,95 @@
(format #f fmt args ...)
form))))
(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."
(with-syntax ((type type)
(name name)
(ctor ctor)
(expected fields)
(defaults defaults))
#`(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.
(define (field-inherited-value f)
(and=> (find (lambda (x)
(eq? f (car (syntax->datum x))))
field+value)
car))
;; Make sure there are no unknown field names.
(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"
unexpected)))
#`(make-struct type 0
#,@(map (lambda (field index)
(or (field-inherited-value field)
#`(struct-ref #,orig-record
#,index)))
'expected
(iota (length 'expected)))))
(define (thunked-field? f)
(memq (syntax->datum f) '#,thunked))
(define (field-bindings field+value)
;; Return field to value bindings, for use in 'let*' below.
(map (lambda (field+value)
(syntax-case field+value ()
((field value)
#`(field
#,(if (thunked-field? #'field)
#'(lambda () value)
#'value)))))
field+value))
(syntax-case s (inherit #,@fields)
((_ (inherit orig-record) (field value) (... ...))
#`(let* #,(field-bindings #'((field value) (... ...)))
#,(record-inheritance #'orig-record
#'((field value) (... ...)))))
((_ (field value) (... ...))
(let ((fields (map syntax->datum #'(field (... ...))))
(dflt (map (match-lambda
((f v)
(list (syntax->datum f) v)))
#'defaults)))
(define (field-value f)
(or (and=> (find (lambda (x)
(eq? f (car (syntax->datum x))))
#'((field value) (... ...)))
car)
(let ((value
(car (assoc-ref dflt (syntax->datum f)))))
(if (thunked-field? f)
#`(lambda () #,value)
value))))
(let ((fields (append fields (map car dflt))))
(cond ((lset= eq? fields 'expected)
#`(let* #,(field-bindings
#'((field value) (... ...)))
(ctor #,@(map field-value 'expected))))
((pair? (lset-difference eq? fields 'expected))
(record-error 'name s
"extraneous field initializers ~a"
(lset-difference eq? fields
'expected)))
(else
(record-error 'name s
"missing field initializers ~a"
(lset-difference eq? 'expected
fields))))))))))))
(define-syntax define-record-type*
(lambda (s)
"Define the given record type such that an additional \"syntactic
@ -78,99 +167,6 @@ It is possible to copy an object 'x' created with 'thing' like this:
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."
(with-syntax ((type type)
(name name)
(ctor ctor)
(expected fields)
(defaults defaults))
#`(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.
(define (field-inherited-value f)
(and=> (find (lambda (x)
(eq? f (car (syntax->datum x))))
field+value)
car))
;; Make sure there are no unknown field names.
(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"
unexpected)))
#`(make-struct type 0
#,@(map (lambda (field index)
(or (field-inherited-value field)
#`(struct-ref #,orig-record
#,index)))
'expected
(iota (length 'expected)))))
(define (thunked-field? f)
(memq (syntax->datum f) '#,thunked))
(define (field-bindings field+value)
;; Return field to value bindings, for use in 'let*' below.
(map (lambda (field+value)
(syntax-case field+value ()
((field value)
#`(field
#,(if (thunked-field? #'field)
#'(lambda () value)
#'value)))))
field+value))
(syntax-case s (inherit #,@fields)
((_ (inherit orig-record) (field value) (... ...))
#`(let* #,(field-bindings #'((field value) (... ...)))
#,(record-inheritance #'orig-record
#'((field value) (... ...)))))
((_ (field value) (... ...))
(let ((fields (map syntax->datum #'(field (... ...))))
(dflt (map (match-lambda
((f v)
(list (syntax->datum f) v)))
#'defaults)))
(define (field-value f)
(or (and=> (find (lambda (x)
(eq? f (car (syntax->datum x))))
#'((field value) (... ...)))
car)
(let ((value
(car (assoc-ref dflt
(syntax->datum f)))))
(if (thunked-field? f)
#`(lambda () #,value)
value))))
(let ((fields (append fields (map car dflt))))
(cond ((lset= eq? fields 'expected)
#`(let* #,(field-bindings
#'((field value) (... ...)))
(ctor #,@(map field-value 'expected))))
((pair? (lset-difference eq? fields 'expected))
(record-error 'name s
"extraneous field initializers ~a"
(lset-difference eq? fields
'expected)))
(else
(record-error 'name s
"missing field initializers ~a"
(lset-difference eq? 'expected
fields))))))))))))
(define (field-default-value s)
(syntax-case s (default)
((field (default val) _ ...)