src/Pure/ML-Systems/polyml_common.ML

 (*  Title:      Pure/ML-Systems/polyml_common.ML
 
 Compatibility file for Poly/ML -- common part for 5.x.
 *)
+
+fun op before (a, _: unit) = a;
 
 exception Interrupt = SML90.Interrupt;
 
 use "General/exn.ML";