tasks a-s

Task/Named-parameters/Scheme/named-parameters-1.ss

@@ -0,0 +1,21 @@
+(define (keyarg-parser argdefs args kont)
+  (apply kont
+	 (map (lambda (argdef)
+		(let loop ((args args))
+		  (cond ((null? args)
+			 (cadr argdef))
+			((eq? (car argdef) (car args))
+			 (cadr args))
+			(else
+			 (loop (cdr args))))))
+	      argdefs)))
+
+(define (print-name . args)
+  (keyarg-parser '((first #f)(last "?"))
+		 args
+		 (lambda (first last)
+		   (display last)
+		   (cond (first
+			  (display ", ")
+			  (display first)))
+		   (newline))))

Task/Named-parameters/Scheme/named-parameters-2.ss

@@ -0,0 +1,8 @@
+=> (print-name)
+?
+=> (print-name 'first "John")
+?, John
+=>(print-name 'first "John" 'last "Doe")
+Doe, John
+=>(print-name 'last "Doe")
+Doe