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authorEric Bavier <bavier@member.fsf.org>2016-09-20 15:41:31 -0500
committerEric Bavier <bavier@member.fsf.org>2016-10-07 07:42:05 -0500
commitb8b129ebd8d017c957094f3d977a1c452d7d450f (patch)
tree5fa5860e6e7725c1cffae5da6b282ef82bb09e07 /guix
parent347df60158a11abbc9b84ac36cd113362d7e09e0 (diff)
utils: Support defaults in substitute-keyword-arguments.
* guix/utils.scm (collect-default-args, expand-default-args): New syntax. (substitute-keyword-arguments): Allow default value declarations. * tests/utils.scm (substitute-keyword-arguments): New test.
Diffstat (limited to 'guix')
-rw-r--r--guix/utils.scm19
1 files changed, 15 insertions, 4 deletions
diff --git a/guix/utils.scm b/guix/utils.scm
index ded31142aa..decadf64a6 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -375,13 +375,24 @@ keywords not already present in ARGS."
(()
args))))
+(define-syntax collect-default-args
+ (syntax-rules ()
+ ((_)
+ '())
+ ((_ (_ _) rest ...)
+ (collect-default-args rest ...))
+ ((_ (kw _ dflt) rest ...)
+ (cons* kw dflt (collect-default-args rest ...)))))
+
(define-syntax substitute-keyword-arguments
(syntax-rules ()
"Return a new list of arguments where the value for keyword arg KW is
-replaced by EXP. EXP is evaluated in a context where VAR is boud to the
-previous value of the keyword argument."
- ((_ original-args ((kw var) exp) ...)
- (let loop ((args original-args)
+replaced by EXP. EXP is evaluated in a context where VAR is bound to the
+previous value of the keyword argument, or DFLT if given."
+ ((_ original-args ((kw var dflt ...) exp) ...)
+ (let loop ((args (default-keyword-arguments
+ original-args
+ (collect-default-args (kw var dflt ...) ...)))
(before '()))
(match args
((kw var rest (... ...))