Merge pull request #332 from bovi/printf-not-implemented

Sprintf NotImplementedError

mrblib/print.rb

@@ -48,12 +48,24 @@ module Kernel
     args[0]
   end
 
-  if Kernel.respond_to?(:sprintf)
   ##
   # Invoke method +sprintf+ and pass +*args+ to it.
-    # Pass return value to *print* of STDOUT.
+  # Pass return value to +print+ of STDOUT.
   def printf(*args)
+    if Kernel.respond_to?(:sprintf)
       __printstr__(sprintf(*args))
+    else
+      raise NotImplementedError.new('sprintf not available')
+    end
+  end
+
+  ##
+  # +sprintf+ is defined in +src/sprintf.c+
+  # This stub method is only to inform the user
+  # that +sprintf+ isn't implemented.
+  unless Kernel.respond_to?(:sprintf)
+    def sprintf(*args)
+      raise NotImplementedError.new('sprintf not available')
     end
   end
 end