src/Pure/type.ML

   val subsort: tsig -> sort * sort -> bool
   val of_sort: tsig -> typ * sort -> bool
   val inter_sort: tsig -> sort * sort -> sort
   val cert_class: tsig -> class -> class
   val cert_sort: tsig -> sort -> sort
+  val minimize_sort: tsig -> sort -> sort
   val witness_sorts: tsig -> (typ * sort) list -> sort list -> (typ * sort) list
   type mode
   val mode_default: mode
   val mode_syntax: mode
   val mode_abbrev: mode

 fun of_sort (TSig {classes, ...}) = Sorts.of_sort (#2 classes);
 fun inter_sort (TSig {classes, ...}) = Sorts.inter_sort (#2 classes);
 
 fun cert_class (TSig {classes, ...}) = Sorts.certify_class (#2 classes);
 fun cert_sort (TSig {classes, ...}) = Sorts.certify_sort (#2 classes);
+fun minimize_sort (TSig {classes, ...}) = Sorts.minimize_sort (#2 classes);
 
 fun witness_sorts (TSig {classes, log_types, ...}) =
   Sorts.witness_sorts (#2 classes) log_types;