src/Pure/Isar/ROOT.ML

     Author:     Markus Wenzel, TU Muenchen
 
 Isar -- Intelligible Semi-Automated Reasoning for Isabelle.
 *)
 
-(*proof engine*)
+(*basic proof engine*)
 use "auto_bind.ML";
 use "proof_context.ML";
 use "proof.ML";
 use "proof_data.ML";
 use "proof_history.ML";
 use "args.ML";
 use "attrib.ML";
 use "method.ML";
+
+(*derived proof elements*)
 use "calculation.ML";
+use "skip_proof.ML";
 
 (*outer syntax*)
 use "comment.ML";
 use "outer_lex.ML";
 use "outer_parse.ML";