ccwl: Document default default value of syntax-lambda**.

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

2 files changed, 12 insertions, 1 deletions

diff --git a/ccwl/utils.scm b/ccwl/utils.scm
index db74c7f..04938b1 100644
--- a/ccwl/utils.scm
+++ b/ccwl/utils.scm
@@ -252,7 +252,8 @@ number of positional arguments is passed, a
 => (#'1 #'2 #'123 (#'1 #'2 #'3))
 
 Like lambda**, syntax-lambda** supports default values for
-arguments. For example,
+arguments. The default default value for unary arguments is #f, while
+that for n-ary arguments is the empty list. For example,
 
 ((syntax-lambda** (foo aal #:key vale (pal 9) #:key* naal (irandu 7) (sol 3 2 1))
    (list foo aal vale pal naal irandu sol))
diff --git a/tests/utils.scm b/tests/utils.scm
index 6b14f29..3970a5c 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -132,6 +132,16 @@
              (list foo aal vale pal naal irandu sol))
            #'1 #'2 #'#:vale #'123 #'#:naal #'321 #'456)))
 
+(test-equal "default default value of syntax-lambda** unary argument should be #f"
+  #f
+  ((syntax-lambda** (#:key foo)
+     foo)))
+
+(test-equal "default default value of syntax-lambda** n-ary argument should be the empty list"
+  '()
+  ((syntax-lambda** (#:key* foo)
+     foo)))
+
 ;; We cannot use test-equal to compare syntax objects, since
 ;; test-equal does not preserve the lexical contexts of the test
 ;; expressions.