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Add `define-record-type*'.

* guix/utils.scm (define-record-type*): New macro.

* tests/utils.scm ("define-record-type*"): New test.
wip-grafts
Ludovic Courtès 10 years ago
parent
commit
72d869634b
  1. 63
      guix/utils.scm
  2. 16
      tests/utils.scm

63
guix/utils.scm

@ -18,6 +18,7 @@
(define-module (guix utils)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-26)
#:use-module (srfi srfi-39)
#:use-module (srfi srfi-60)
@ -27,6 +28,7 @@
#:autoload (ice-9 popen) (open-pipe*)
#:autoload (ice-9 rdelim) (read-line)
#:use-module (ice-9 regex)
#:use-module (ice-9 match)
#:use-module ((chop hash)
#:select (bytevector-hash
hash-method/sha256))
@ -42,6 +44,7 @@
%nixpkgs-directory
nixpkgs-derivation
define-record-type*
memoize
gnu-triplet->nix-system
%current-system))
@ -391,6 +394,66 @@ starting from the right of S."
;;; Miscellaneous.
;;;
(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."
(define (make-syntactic-constructor name ctor fields defaults)
"Make the syntactic constructor NAME that calls CTOR, and expects all
of FIELDS to be initialized. DEFAULTS is the list of FIELD/DEFAULT-VALUE
tuples."
(with-syntax ((name name)
(ctor ctor)
(expected fields)
(defaults defaults))
#'(define-syntax name
(lambda (s)
(syntax-case s expected
((_ (field value) (... ...))
(let ((fields (map syntax->datum #'(field (... ...))))
(inits (map (match-lambda
((f v)
(list (syntax->datum f) v)))
#'((field value) (... ...))))
(dflt (map (match-lambda
((f v)
(list (syntax->datum f) v)))
#'defaults)))
(define (field-value f)
(match (assoc f inits)
((_ v) v)
(#f (car (assoc-ref dflt f)))))
(if (lset= eq? (append fields (map car dflt))
'expected)
#`(ctor #,@(map field-value 'expected))
(error "missing or extraneous field initializers"
(lset-difference eq? fields 'expected))))))))))
(define (field-default-value s)
(syntax-case s (default)
((field (default val) _ ...)
(list #'field #'val))
((field _ options ...)
(field-default-value #'(field options ...)))
(_ #f)))
(syntax-case s ()
((_ type syntactic-ctor ctor pred
(field get options ...) ...)
#`(begin
(define-record-type type
(ctor field ...)
pred
(field get) ...)
#,(make-syntactic-constructor #'syntactic-ctor #'ctor
#'(field ...)
(filter-map field-default-value
#'((field options ...)
...))))))))
(define (memoize proc)
"Return a memoizing version of PROC."
(let ((cache (make-hash-table)))

16
tests/utils.scm

@ -26,7 +26,8 @@
#:use-module (rnrs bytevectors)
#:use-module (rnrs io ports)
#:use-module (ice-9 rdelim)
#:use-module (ice-9 popen))
#:use-module (ice-9 popen)
#:use-module (ice-9 match))
(test-begin "utils")
@ -98,6 +99,19 @@
(equal? nix (gnu-triplet->nix-system gnu)))
gnu nix))))
(test-assert "define-record-type*"
(begin
(define-record-type* <foo> foo make-foo
foo?
(bar foo-bar)
(baz foo-baz (default (+ 40 2))))
(and (match (foo (bar 1) (baz 2))
(($ <foo> 1 2) #t))
(match (foo (baz 2) (bar 1))
(($ <foo> 1 2) #t))
(match (foo (bar 1))
(($ <foo> 1 42) #t)))))
(test-end)

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