(*
    ||M||  This file is part of HELM, an Hypertextual, Electronic        
    ||A||  Library of Mathematics, developed at the Computer Science     
    ||T||  Department, University of Bologna, Italy.                     
    ||I||                                                                
    ||T||  HELM is free software; you can redistribute it and/or         
    ||A||  modify it under the terms of the GNU General Public License   
    \   /  version 2 or (at your option) any later version.      
     \ /   This software is distributed as is, NO WARRANTY.     
      V_______________________________________________________________ *)

(* $Id: terms.ml 9836 2009-06-05 15:33:35Z denes $ *)

let rec lexicograph f l1 l2 =
  match l1, l2 with
  | [], [] -> 0
  | x::xs, y::ys ->
     let c = f x y in
     if c <> 0 then c else lexicograph f xs ys
  | [],_ -> ~-1
  | _,[] -> 1
;;
  
module Utils (B : Terms.Blob) = struct
  module Subst = FoSubst;; 

  let rec eq_foterm x y =
    x == y ||
    match x, y with
    | Terms.Leaf t1, Terms.Leaf t2 -> B.eq t1 t2
    | Terms.Var i, Terms.Var j -> i = j
    | Terms.Node l1, Terms.Node l2 -> List.for_all2 eq_foterm l1 l2
    | _ -> false
  ;;


  let rec compare_foterm x y =
    match x, y with
    | Terms.Leaf t1, Terms.Leaf t2 -> B.compare t1 t2
    | Terms.Var i, Terms.Var j -> i - j
    | Terms.Node l1, Terms.Node l2 -> lexicograph compare_foterm l1 l2
    | Terms.Leaf _, ( Terms.Node _ | Terms.Var _ ) -> ~-1
    | Terms.Node _, Terms.Leaf _ -> 1
    | Terms.Node _, Terms.Var _ -> ~-1
    | Terms.Var _, _ ->  1
  ;;

  let eq_literal l1 l2 =
    match l1, l2 with
    | Terms.Predicate p1, Terms.Predicate p2 -> eq_foterm p1 p2
    | Terms.Equation (l1,r1,ty1,o1), Terms.Equation (l2,r2,ty2,o2) ->
        o1 = o2 && eq_foterm l1 l2 && eq_foterm r1 r2 && eq_foterm ty1 ty2
    | _ -> false
  ;;

  let compare_literal l1 l2 =
    match l1, l2 with
    | Terms.Predicate p1, Terms.Predicate p2 -> compare_foterm p1 p2
    | Terms.Equation (l1,r1,ty1,o1), Terms.Equation (l2,r2,ty2,o2) ->
        let c = Pervasives.compare o1 o2 in
        if c <> 0 then c else
          let c = compare_foterm l1 l2 in
          if c <> 0 then c else
            let c = compare_foterm r1 r2 in
            if c <> 0 then c else
              compare_foterm ty1 ty2
    | Terms.Predicate _, Terms.Equation _ -> ~-1
    | Terms.Equation _, Terms.Predicate _ -> 1
  ;;

  let relocate maxvar varlist subst =
    List.fold_right
      (fun i (maxvar, varlist, s) -> 
         maxvar+1, maxvar::varlist, Subst.build_subst i (Terms.Var maxvar) s)
      varlist (maxvar+1, [], subst)
  ;;

end