anchor.diff:  //   ("\/", bool->bool->bool); ("?", (A->bool)->bool); ("!", (A->bool)->bool);
   //   ("==>", bool->bool->bool); ("/\", bool->bool->bool); ("T", bool);
   //   ("=", A->A->bool)]
  +infixes();;
  +//val it : (string * (int * string)) list =
  +//  [("<=>", (2, "right")); ("==>", (4, "right")); ("\/", (6, "right"));
  +//   ("/\", (8, "right")); ("=", (12, "right")); (",", (14, "right"))]
   axioms();;                                                                          // the_axioms database doesn't change
   definitions();;                                                                     // the_definitions doesn't change
   !the_implicit_types;;                                                               // no change
  
positive.code: (*
  
  Copyright 2013 Domenico D. D. Masini
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  
negative.code: //   ("F", bool); ("\/", bool->bool->bool); ("?", (A->bool)->bool);
  //   ("!", (A->bool)->bool); ("==>", bool->bool->bool); ("/\", bool->bool->bool);
  //   ("T", bool); ("=", A->A->bool)]
  axioms();;                                                                          // new axioms: SELECT, ETA
  //  [|- !P x. P x ==> P ((@) P); |- !t. (\x. t x) = t]
  definitions();;                                                                     // new COND definition
  //  [|- COND = (\t t1 t2. @x. ((t <=> T) ==> x = t1) /\ ((t <=> F) ==> x = t2));
  