src/ZF/Tools/induct_tacs.ML

 (**** declare non-datatype as datatype ****)
 
 fun rep_datatype_i elim induct case_eqns recursor_eqns thy =
   let
     (*analyze the LHS of a case equation to get a constructor*)
-    fun const_of (Const("op =", _) $ (_ $ c) $ _) = c
+    fun const_of (Const(@{const_name "op ="}, _) $ (_ $ c) $ _) = c
       | const_of eqn = error ("Ill-formed case equation: " ^
                               Syntax.string_of_term_global thy eqn);
 
     val constructors =
         map (head_of o const_of o FOLogic.dest_Trueprop o