(* ========================================================================= *)
(* FIRST ORDER LOGIC SUBSTITUTIONS *)
(* Copyright (c) 2002-2006 Joe Hurd, distributed under the GNU GPL version 2 *)
(* ========================================================================= *)
signature Subst =
sig
(* ------------------------------------------------------------------------- *)
(* A type of first order logic substitutions. *)
(* ------------------------------------------------------------------------- *)
type subst
(* ------------------------------------------------------------------------- *)
(* Basic operations. *)
(* ------------------------------------------------------------------------- *)
val empty : subst
val null : subst -> bool
val size : subst -> int
val peek : subst -> Term.var -> Term.term option
val insert : subst -> Term.var * Term.term -> subst
val singleton : Term.var * Term.term -> subst
val union : subst -> subst -> subst
val toList : subst -> (Term.var * Term.term) list
val fromList : (Term.var * Term.term) list -> subst
val foldl : (Term.var * Term.term * 'a -> 'a) -> 'a -> subst -> 'a
val foldr : (Term.var * Term.term * 'a -> 'a) -> 'a -> subst -> 'a
val pp : subst Parser.pp
val toString : subst -> string
(* ------------------------------------------------------------------------- *)
(* Normalizing removes identity substitutions. *)
(* ------------------------------------------------------------------------- *)
val normalize : subst -> subst
(* ------------------------------------------------------------------------- *)
(* Applying a substitution to a first order logic term. *)
(* ------------------------------------------------------------------------- *)
val subst : subst -> Term.term -> Term.term
(* ------------------------------------------------------------------------- *)
(* Restricting a substitution to a smaller set of variables. *)
(* ------------------------------------------------------------------------- *)
val restrict : subst -> NameSet.set -> subst
val remove : subst -> NameSet.set -> subst
(* ------------------------------------------------------------------------- *)
(* Composing two substitutions so that the following identity holds: *)
(* *)
(* subst (compose sub1 sub2) tm = subst sub2 (subst sub1 tm) *)
(* ------------------------------------------------------------------------- *)
val compose : subst -> subst -> subst
(* ------------------------------------------------------------------------- *)
(* Substitutions can be inverted iff they are renaming substitutions. *)
(* ------------------------------------------------------------------------- *)
val invert : subst -> subst (* raises Error *)
val isRenaming : subst -> bool
(* ------------------------------------------------------------------------- *)
(* Creating a substitution to freshen variables. *)
(* ------------------------------------------------------------------------- *)
val freshVars : NameSet.set -> subst
(* ------------------------------------------------------------------------- *)
(* Matching for first order logic terms. *)
(* ------------------------------------------------------------------------- *)
val match : subst -> Term.term -> Term.term -> subst (* raises Error *)
(* ------------------------------------------------------------------------- *)
(* Unification for first order logic terms. *)
(* ------------------------------------------------------------------------- *)
val unify : subst -> Term.term -> Term.term -> subst (* raises Error *)
end