Parameterize over error message in make-simple-default-setter

scheme/httpd/surflets/surflet-input-fields.scm

@@ -39,13 +39,13 @@
 		 ,(field-attributes-default attributes)
 		 ,(field-attributes-others attributes))))))
 
-(define (make-simple-default-setter default-pred?)
+(define (make-simple-default-setter default-pred? error-msg-types)
   (lambda (input-field value)
     (if (default-pred? value)
 	(set-field-attributes-default! 
 	 (input-field-attributes input-field) 
 	 `(value ,value))
-	(error "Default value must be a number or a string or a symbol." 
+	(error (format #f "Default value must be ~a." error-msg-types) 
 	       value))
     (touch-input-field! input-field)))
 
@@ -54,7 +54,7 @@
 (define simple-default? string-or-symbol?)
 
 (define set-simple-field-default! 
-  (make-simple-default-setter simple-default?))
+  (make-simple-default-setter simple-default? "a string or a symbol"))
 
 (define (second-arg first second) second)
 
@@ -76,7 +76,8 @@
   (simple-field-maker "text" "number" 
 		      number-field-default? number-field-transformer))
 (define set-number-field-value!
-  (make-simple-default-setter number-field-default?))
+  (make-simple-default-setter number-field-default? 
+			      "a number a string or a symbol"))
 
 ;;;;;;;;;;;;;;;;;;;;;;
 ;;; hidden input-field