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01/03: guix: records: Add match-record.
From: |
Ludovic Courtès |
Subject: |
01/03: guix: records: Add match-record. |
Date: |
Sun, 5 Nov 2017 09:31:02 -0500 (EST) |
civodul pushed a commit to branch master
in repository guix.
commit 6692d8454a89e542d85d2b6a93adfd373aeec39c
Author: nee <address@hidden>
Date: Wed Oct 25 20:44:54 2017 +0200
guix: records: Add match-record.
* guix/records.scm: New syntax-rule.
Signed-off-by: Ludovic Courtès <address@hidden>
---
guix/records.scm | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/guix/records.scm b/guix/records.scm
index 7de5fcc..1f00e16 100644
--- a/guix/records.scm
+++ b/guix/records.scm
@@ -26,7 +26,8 @@
#:export (define-record-type*
alist->record
object->fields
- recutils->alist))
+ recutils->alist
+ match-record))
;;; Commentary:
;;;
@@ -375,4 +376,19 @@ pairs. Stop upon an empty line (after consuming it) or
EOF."
(else
(error "unmatched line" line))))))))
+(define-syntax match-record
+ (syntax-rules ()
+ "Bind each FIELD of a RECORD of the given TYPE to it's FIELD name.
+The current implementation does not support thunked and delayed fields."
+ ((_ record type (field fields ...) body ...)
+ (if (eq? (struct-vtable record) type)
+ ;; TODO compute indices and report wrong-field-name errors at
+ ;; expansion time
+ ;; TODO support thunked and delayed fields
+ (let ((field ((record-accessor type 'field) record)))
+ (match-record record type (fields ...) body ...))
+ (throw 'wrong-type-arg record)))
+ ((_ record type () body ...)
+ (begin body ...))))
+
;;; records.scm ends here