src/Pure/sign.ML

Initial revision

(*  Title: 	sign
    ID:         $Id$
    Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
    Copyright   1992  University of Cambridge

  the abstract types "sg" (signatures)
  and "cterm" (certified terms under a signature)
*)

signature SIGN = 
sig
  structure Type: TYPE
  structure Symtab: SYMTAB
  structure Syntax: SYNTAX
  sharing Symtab=Type.Symtab
  type sg
  type cterm
  type ctyp
  val cfun: (term -> term) -> (cterm -> cterm)
  val cterm_of: sg -> term -> cterm
  val ctyp_of: sg -> typ -> ctyp
  val extend: sg -> string ->
	(class * class list) list * class list *
	(string list * int) list *
	(string list * (sort list * class)) list *
	(string list * string)list * Syntax.sext option -> sg
  val merge: sg * sg -> sg
  val pure: sg
  val read_cterm: sg -> string * typ -> cterm
  val read_ctyp: sg -> string -> ctyp
  val read_insts: sg -> (indexname -> typ option) * (indexname -> sort option)
	          -> (indexname -> typ option) * (indexname -> sort option)
		  -> (string*string)list
		  -> (indexname*ctyp)list * (cterm*cterm)list
  val read_typ: sg * (indexname -> sort option) -> string -> typ
  val rep_cterm: cterm -> {T: typ, t: term, sign: sg, maxidx: int}
  val rep_ctyp: ctyp -> {T: typ, sign: sg}
  val rep_sg: sg -> {tsig: Type.type_sig,
		     const_tab: typ Symtab.table,
		     syn: Syntax.syntax,
		     stamps: string ref list}
  val string_of_cterm: cterm -> string
  val string_of_ctyp: ctyp -> string
  val pprint_cterm: cterm -> pprint_args -> unit
  val pprint_ctyp: ctyp -> pprint_args -> unit
  val string_of_term: sg -> term -> string
  val string_of_typ: sg -> typ -> string
  val pprint_term: sg -> term -> pprint_args -> unit
  val pprint_typ: sg -> typ -> pprint_args -> unit
  val term_of: cterm -> term
  val typ_of: ctyp -> typ
  val pretty_term: sg -> term -> Syntax.Pretty.T
end;


functor SignFun (structure Type:TYPE and Syntax:SYNTAX) : SIGN = 
struct
structure Type = Type;
structure Symtab = Type.Symtab;
structure Syntax = Syntax;
structure Pretty = Syntax.Pretty

(*Signatures of theories. *)
datatype sg = 
  Sg of {tsig: Type.type_sig,		(* order-sorted signature of types *)
	 const_tab: typ Symtab.table,	(*types of constants*)
	 syn: Syntax.syntax,		(*Parsing and printing operations*)
	 stamps: string ref list	(*unique theory indentifier*)  };


fun rep_sg (Sg args) = args;

fun string_of_typ(Sg{tsig,syn,...}) = Syntax.string_of_typ syn;

fun pprint_typ(Sg{syn,...}) = Pretty.pprint o Pretty.quote o (Syntax.pretty_typ syn);

(*Is constant present in table with more generic type?*)
fun valid_const tsig ctab (a,T) = case Symtab.lookup(ctab, a) of
	Some U => Type.typ_instance(tsig,T,U) | _ => false;


(*Check a term for errors.  Are all constants and types valid in signature?
  Does not check that term is well-typed!*)
fun term_errors (sign as Sg{tsig,const_tab,...}) = 
let val showtyp = string_of_typ sign;
    fun terrs (Const (a,T), errs) =
	if valid_const tsig const_tab (a,T)
	then Type.type_errors (tsig,showtyp) (T,errs)
	else ("Illegal type for constant: " ^ a ^ ": " ^ showtyp T) :: errs
      | terrs (Free (_,T), errs) = Type.type_errors (tsig,showtyp) (T,errs)
      | terrs (Var  ((a,i),T), errs) =
	if  i>=0  then  Type.type_errors (tsig,showtyp) (T,errs)
	else  ("Negative index for Var: " ^ a) :: errs
      | terrs (Bound _, errs) = errs (*loose bvars detected by type_of*)
      | terrs (Abs (_,T,t), errs) = 
	    Type.type_errors(tsig,showtyp)(T,terrs(t,errs))
      | terrs (f$t, errs) = terrs(f, terrs (t,errs))
in  terrs  end;


(** The Extend operation **)


(*Reset TVar indices to zero, renaming to preserve distinctness*)
fun zero_tvar_indices tsig T = 
  let val inxSs = typ_tvars T;
      val nms' = variantlist(map (#1 o #1) inxSs,[]);
      val tye = map (fn ((v,S),a) => (v, TVar((a,0),S))) (inxSs ~~ nms')
  in typ_subst_TVars tye T end

(*Check that all types mentioned in the list of declarations are valid.
  If errors found then raise exception.
  Zero type var indices because type inference requires it.
*)
fun read_consts(tsig,syn) =
let val showtyp = Syntax.string_of_typ syn;
    fun read [] = []
      | read((cs,s)::pairs) =
	let val t = Syntax.read syn Syntax.typeT s handle ERROR =>
	            error("The error above occurred in type " ^ s);
	    val S = Type.defaultS tsig;
	    val T = Type.varifyT(Syntax.typ_of_term (K S) t)
	    val T0 = zero_tvar_indices tsig T;
	in (case Type.type_errors (tsig,showtyp) (T0,[]) of
		[] => (cs,T0) :: read pairs
	    | errs => error (cat_lines
 	   (("Error in type of constants " ^ space_implode " " cs) :: errs)))
	end
in read end;


(*Extend a signature: may add classes, types and constants.
  Replaces syntax with "syn".
  The "ref" in stamps ensures that no two signatures are identical --
  it is impossible to forge a signature.  *)
fun extend (Sg{tsig, const_tab, syn, stamps, ...}) signame
	   (newclasses, newdefault, otypes, newtypes, const_decs, osext) : sg =
let val tsig' = Type.extend(tsig,newclasses,newdefault,otypes,newtypes);
    val S = Type.defaultS tsig';
    val roots = filter (Type.logical_type tsig')
		       (distinct(flat(map #1 newtypes)))
    val xconsts = map #1 newclasses @ flat (map #1 otypes) @ flat (map #1 const_decs);
    val syn' =
      case osext of
        Some sext => Syntax.extend (syn, K S) (roots, xconsts, sext)
      | None => if null roots andalso null xconsts then syn
                else Syntax.extend (syn, K S) (roots, xconsts, Syntax.empty_sext);
    val sconsts = case osext of
		    Some(sext) => Syntax.constants sext
		  | None => [];
    val const_decs' = read_consts(tsig',syn') (sconsts @ const_decs)
in Sg{tsig= tsig',
      const_tab= Symtab.st_of_declist (const_decs', const_tab)
		 handle Symtab.DUPLICATE(a) =>
		 error("Constant '" ^ a ^ "' declared twice"), 
      syn=syn', stamps= ref signame :: stamps}
end;


(* The empty signature *)
val sg0 = Sg{tsig= Type.tsig0, const_tab= Symtab.null,
	     syn=Syntax.type_syn,  stamps= []};

(*The pure signature*)
val pure : sg = extend sg0 "Pure"
([("logic", [])],
 ["logic"],
 [(["fun"],2),
  (["prop"],0),
  (Syntax.syntax_types,0)],
 [(["fun"],  ([["logic"], ["logic"]], "logic")),
  (["prop"], ([], "logic"))],
 [(["*NORMALIZED*"], "'a::{} => 'a"),
  ([Syntax.constrainC], "'a::logic => 'a")],
 Some(Syntax.pure_sext)
);


(** The Merge operation **)

(*Update table with (a,x) providing any existing asgt to "a" equals x. *)
fun update_eq ((a,x),tab) =
    case Symtab.lookup(tab,a) of
	None => Symtab.update((a,x), tab)
      | Some y => if x=y then tab 
	    else  raise TERM ("Incompatible types for constant: "^a, []);

(*Combine tables, updating tab2 by tab1 and checking.*)
fun merge_tabs (tab1,tab2) = 
    Symtab.balance (foldr update_eq (Symtab.alist_of tab1, tab2));

(*Combine tables, overwriting tab2 with tab1.*)
fun smash_tabs (tab1,tab2) = 
    Symtab.balance (foldr Symtab.update (Symtab.alist_of tab1, tab2));

(*Combine stamps, checking that theory names are disjoint. *)
fun merge_stamps (stamps1,stamps2) = 
  let val stamps = stamps1 union stamps2 in
  case findrep (map ! stamps) of
     a::_ => error ("Attempt to merge different versions of theory: " ^ a)
   | [] => stamps
  end;

(*Merge two signatures.  Forms unions of tables.  Prefers sign1. *)
fun merge (sign1 as Sg{tsig=tsig1,const_tab=ctab1,stamps=stamps1,syn=syn1},
	   sign2 as Sg{tsig=tsig2,const_tab=ctab2,stamps=stamps2,syn=syn2}) =
    if stamps2 subset stamps1 then sign1
    else if stamps1 subset stamps2 then sign2
    else  (*neither is union already;  must form union*)
	   Sg{tsig= Type.merge(tsig1,tsig2),
	      const_tab= merge_tabs (ctab1, ctab2),
	      stamps= merge_stamps (stamps1,stamps2),
	      syn = Syntax.merge(syn1,syn2)};


(**** CERTIFIED TYPES ****)


(*Certified typs under a signature*)
datatype ctyp = Ctyp of {sign: sg,  T: typ};

fun rep_ctyp(Ctyp ctyp) = ctyp;

fun typ_of (Ctyp{sign,T}) = T;

fun ctyp_of (sign as Sg{tsig,...}) T =
	case Type.type_errors (tsig,string_of_typ sign) (T,[]) of
	  [] => Ctyp{sign= sign,T= T}
	| errs =>  error (cat_lines ("Error in type:" :: errs));

(*The only use is a horrible hack in the simplifier!*)
fun read_typ(Sg{tsig,syn,...}, defS) s =
    let val term = Syntax.read syn Syntax.typeT s;
	val S0 = Type.defaultS tsig;
	fun defS0 s = case defS s of Some S => S | None => S0;
    in Syntax.typ_of_term defS0 term end;

fun read_ctyp sign = ctyp_of sign o read_typ(sign, K None);

fun string_of_ctyp (Ctyp{sign,T}) = string_of_typ sign T;

fun pprint_ctyp (Ctyp{sign,T}) = pprint_typ sign T;


(**** CERTIFIED TERMS ****)

(*Certified terms under a signature, with checked typ and maxidx of Vars*)
datatype cterm = Cterm of {sign: sg,  t: term,  T: typ,  maxidx: int};

fun rep_cterm (Cterm args) = args;

(*Return the underlying term*)
fun term_of (Cterm{sign,t,T,maxidx}) = t;

(** pretty printing of terms **)

fun pretty_term (Sg{tsig,syn,...}) = Syntax.pretty_term syn;

fun string_of_term sign t = Pretty.string_of (pretty_term sign t);

fun pprint_term sign = Pretty.pprint o Pretty.quote o (pretty_term sign);

fun string_of_cterm (Cterm{sign,t,...}) = string_of_term sign t;

fun pprint_cterm (Cterm{sign,t,...}) = pprint_term sign t;

(*Create a cterm by checking a "raw" term with respect to a signature*)
fun cterm_of sign t =
  case  term_errors sign (t,[])  of
      [] => Cterm{sign=sign, t=t, T= type_of t, maxidx= maxidx_of_term t}
    | errs => raise TERM(cat_lines("Term not in signature"::errs), [t]);

fun cfun f = fn Cterm{sign,t,...} => cterm_of sign (f t);

(*Lexing, parsing, polymorphic typechecking of a term.*)
fun read_def_cterm (sign as Sg{tsig, const_tab, syn,...}, types, sorts)
		   (a,T) =
  let val showtyp = string_of_typ sign
      and showterm = string_of_term sign
      fun termerr [] = ""
	| termerr [t] = "\nInvolving this term:\n" ^ showterm t ^ "\n"
	| termerr ts = "\nInvolving these terms:\n" ^
		       cat_lines (map showterm ts)
      val t = Syntax.read syn T a;
      val (t',tye) = Type.infer_types (tsig, const_tab, types,
				       sorts, showtyp, T, t)
		  handle TYPE (msg, Ts, ts) =>
	  error ("Type checking error: " ^ msg ^ "\n" ^
		  cat_lines (map showtyp Ts) ^ termerr ts)
  in (cterm_of sign t', tye)
  end
  handle TERM (msg, _) => error ("Error: " ^  msg);


fun read_cterm sign = #1 o (read_def_cterm (sign, K None, K None));

(** reading of instantiations **)

fun indexname cs = case Syntax.scan_varname cs of (v,[]) => v
	| _ => error("Lexical error in variable name: " ^ implode cs);

fun absent ixn =
  error("No such variable in term: " ^ Syntax.string_of_vname ixn);

fun inst_failure ixn =
  error("Instantiation of " ^ Syntax.string_of_vname ixn ^ " fails");

fun read_insts (sign as Sg{tsig,...}) (rtypes,rsorts) (types,sorts) insts =
let fun split([],tvs,vs) = (tvs,vs)
      | split((sv,st)::l,tvs,vs) = (case explode sv of
		  "'"::cs => split(l,(indexname cs,st)::tvs,vs)
		| cs => split(l,tvs,(indexname cs,st)::vs));
    val (tvs,vs) = split(insts,[],[]);
    fun readT((a,i),st) =
	let val ixn = ("'" ^ a,i);
	    val S = case rsorts ixn of Some S => S | None => absent ixn;
	    val T = read_typ (sign,sorts) st;
	in if Type.typ_instance(tsig,T,TVar(ixn,S)) then (ixn,T)
	   else inst_failure ixn
	end
    val tye = map readT tvs;
    fun add_cterm ((cts,tye), (ixn,st)) =
	let val T = case rtypes ixn of
		      Some T => typ_subst_TVars tye T
		    | None => absent ixn;
	    val (ct,tye2) = read_def_cterm (sign,types,sorts) (st,T);
	    val cv = cterm_of sign (Var(ixn,typ_subst_TVars tye2 T))
 	in ((cv,ct)::cts,tye2 @ tye) end
    val (cterms,tye') = foldl add_cterm (([],tye), vs);
in (map (fn (ixn,T) => (ixn,ctyp_of sign T)) tye', cterms) end;

end;