error takes just a string

svn: r16071

collects/lang/private/beginner-funs.ss

@@ -464,7 +464,7 @@
     ("Misc"
       (identity (any -> any)
 	"to return the argument unchanged")
-      ((beginner-error error) (symbol string -> void) "to signal an error")
+      ((beginner-error error) (string -> void) "to signal an error")
       ((beginner-struct? struct?) (any -> boolean)
        "to determine whether some value is a structure")
       ((beginner-equal? equal?) (any any -> boolean)

collects/lang/private/teachprims.ss

@@ -184,15 +184,13 @@ namespace.
     (apply append a b x)))
 
 (define-teach beginner error
-  (lambda (sym str)
-    (unless (and (symbol? sym)
-                 (string? str))
+  (lambda (str)
+    (unless  (string? str)
       (raise
        (make-exn:fail:contract
-        (format "error: expected a symbol and a string, got ~e and ~e"
-                sym str)
+        (format "error: expected a string, got ~e and ~e" str)
         (current-continuation-marks))))
-    (error sym "~a" str)))
+    (error str)))
 
 (define-teach beginner struct?
   (lambda (x)