Structure Subst

signature Subst =
sig
  eqtype 'a subs

  val id      : 'a subs
  val cons    : 'a subs * 'a -> 'a subs
  val shift   : int * 'a subs -> 'a subs
  val lift    : int * 'a subs -> 'a subs
  val is_id   : 'a subs -> bool
  val exp_rel : 'a subs * int -> int * 'a option
  val comp    : ('a subs * 'a -> 'a) -> 'a subs * 'a subs -> 'a subs

end

HOL 4, Trindemossen-1