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105 lines
3.2 KiB
OCaml
105 lines
3.2 KiB
OCaml
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(*
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copyright (c) 2013, simon cruanes
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all rights reserved.
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redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer. redistributions in binary
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form must reproduce the above copyright notice, this list of conditions and the
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following disclaimer in the documentation and/or other materials provided with
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the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*)
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(** {1 Rational Terms} *)
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module type SYMBOL = sig
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type t
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val compare : t -> t -> int
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val to_string : t -> string
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end
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module type S = sig
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module Symbol : SYMBOL
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type t = private
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| Var of int
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| Ref of int
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| App of Symbol.t * t list
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type term = t
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type 'a env = 'a RAL.t
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(** Structural equality and comparisons. Two terms being different
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for {!eq} may still be equal, but with distinct representations.
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For instance [r:f(f(r))] and [r:f(r)] are the same term but they
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are not equal structurally. *)
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val eq : t -> t -> bool
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val cmp : t -> t -> int
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val eq_set : t -> t -> bool
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(** Proper equality on terms. This returns [true] if the two terms represent
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the same infinite tree, not only if they have the same shape. *)
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val var : unit -> t
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(** free variable, with a fresh name *)
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val mk_ref : int -> t
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(** Back-ref of [n] levels down (see De Bruijn indices) *)
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val app : Symbol.t -> t list -> t
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(** Application of a symbol to a list, possibly with a unique label *)
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val const : Symbol.t -> t
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(** Shortcut for [app s []] *)
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val pp : Buffer.t -> t -> unit
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val fmt : Format.formatter -> t -> unit
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val to_string : t -> string
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val rename : t -> t
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(** Rename all variables and references to fresh ones *)
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module Subst : sig
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type t
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val empty : t
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val bind : t -> int -> term -> t
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val deref : t -> term -> term
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val apply : ?depth:int -> t -> term -> term
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val pp : Buffer.t -> t -> unit
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val fmt : Format.formatter -> t -> unit
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val to_string : t -> string
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end
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val matching : ?subst:Subst.t -> term -> term -> Subst.t option
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val unify : ?subst:Subst.t -> term -> term -> Subst.t option
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end
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module Make(Sym : SYMBOL) : S with module Symbol = Sym
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module Str : SYMBOL with type t = string
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module Default : sig
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include S with module Symbol = Str
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(* TODO
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val of_string : string -> t option
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val of_string_exn : string -> t (** @raise Failure possibly *)
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*)
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end
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