ccwl: Set default value of lambda** n-ary arguments to '().

* ccwl/utils.scm (lambda**): Set default value of lambda** n-ary
arguments to the empty list. Document this in the docstring.
* tests/utils.scm ("default value of lambda** unary argument should be
#f", "default value of lambda** n-ary argument should be the empty
list"): New tests.

2 files changed, 16 insertions, 5 deletions

diff --git a/ccwl/utils.scm b/ccwl/utils.scm
index c018237..14a3c4d 100644
--- a/ccwl/utils.scm
+++ b/ccwl/utils.scm
@@ -138,12 +138,13 @@ for example, be invoked as:
 => (1 2 123 (1 2 3))
 
 lambda** also supports default values for both unary and n-ary keyword
-arguments. For example,
+arguments. Note that the default value for unary arguments is #f,
+while that for n-ary arguments is the empty list. For example,
 
-((lambda** (foo aal #:key vale (pal 9) #:key* naal (irandu 7) (sol 3 2 1))
-     (list foo aal vale pal naal irandu sol))
+((lambda** (foo bar #:key aal vale (pal 9) #:key* naal (irandu 7) (sol 3 2 1) uruthi)
+     (list foo bar aal vale pal naal irandu sol uruthi))
    1 2 #:vale 123 #:naal 321 456)
-=> (1 2 123 9 (321 456) (7) (3 2 1))"
+=> (1 2 #f 123 9 (321 456) (7) (3 2 1) ())"
     (syntax-case x ()
       ((_ (args-spec ...) body ...)
        #`(lambda args
@@ -160,7 +161,7 @@ arguments. For example,
                                                   (syntax-case x ()
                                                     ((arg defaults ...)
                                                      #'(arg (list defaults ...)))
-                                                    (arg #'arg)))
+                                                    (arg #'(arg '()))))
                                                 nary-arguments))
                           body ...)
                         (let ((positionals rest (break keyword? args)))
diff --git a/tests/utils.scm b/tests/utils.scm
index 5c5bfd1..bc9315d 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -70,6 +70,16 @@
      (list foo aal vale pal naal irandu sol))
    1 2 #:vale 123 #:naal 321 456))
 
+(test-equal "default value of lambda** unary argument should be #f"
+  #f
+  ((lambda** (#:key foo)
+     foo)))
+
+(test-equal "default value of lambda** n-ary argument should be the empty list"
+  '()
+  ((lambda** (#:key* foo)
+     foo)))
+
 (test-assert "syntax-lambda**"
   (equal? (list #'1 #'2 #'123 (list #'1 #'2 #'3))
           ((syntax-lambda** (a b #:key foo #:key* bar)