* Pure/library.ML: several combinators for linear functional transformations;
* Pure/library.ML: canonical list combinators fold, fold_rev, and fold_yield;
* Pure/term.ML: combinators fold_atyps, fold_aterms, fold_term_types, fold_types;
use "../settings.ML";
use_thy "Even";
use_thy "Mutual";
use_thy "Star";
use_thy "AB";
use_thy "Advanced";