#lang sml
(*
 * (c) Andreas Rossberg 1999-2007
 *
 * Standard ML type variables
 *
 * Definition, Sections 2.4 and 4.1
 *)

signature TYVAR =
sig
    (* Import types *)

    type OverloadingClass = OverloadingClass.OverloadingClass

    (* Type [Sections 2.4 and 4.1]*)

    eqtype TyVar			(* [alpha] or [tyvar] *)

    (* Operations *)

    val invent :		bool -> TyVar
    val fromInt :		bool -> int -> TyVar
    val fromString :		string -> TyVar
    val fromOverloadingClass :	string * OverloadingClass -> TyVar
    val toString :		TyVar -> string

    val admitsEquality :	TyVar -> bool
    val overloadingClass :	TyVar -> OverloadingClass option

    val compare :		TyVar * TyVar -> order
end