-- This is the file EXPr.ADB 7:38AM  10/11/95
-- It contains the body of packageexpr, which defines Exp, a type to 
-- implement SymbolicExpressions and all the subtypes needed for 
-- expressions. Constructors, Selectors and
-- Testers are provided. The package expr.io defines put and get
-- on these types. The package eval defines evaluation of expressions.

package body expr is

function MkConst(I : Integer) return Exp is
begin
return new ExpRec'(const, I);
end MkConst;

function MkVar(Name : Symbol) return Exp is
begin
  return new ExpRec'(var, Name);
end MkVar;

function MkDef(Name : Symbol; E : Exp) return Exp is
begin
return new ExpRec'(def, Name, E);
end MkDef;

function MkSet(Name : Symbol; E : Exp) return Exp is
begin
  return new ExpRec'(set, Name, E);
end MkSet;

function MkFcn(FnTyp : FcnType; Name : Symbol; 
		Namelist : SymbolList; FcnBody : Exp) return Exp is
begin
  return new ExpRec'(fcn, FnTyp, Name, NameList, FcnBody);
end MkFcn;

function MkSeq(EL : ExpList) return Exp is
begin
  return new ExpRec'(seq, EL);
end MkSeq;

function MkApp(Op : Exp; ArgList : ExpList) return Exp is
begin
  return new ExpRec'(app, Op, ArgList);
end MkApp;

function MkDummy(Msg : Symbol) return Exp is
  E : Exp;
begin
  return new ExpRec'(done,Msg);
end MkDummy;

function MkEndparen(Msg : Symbol) return Exp is
begin
  return new ExpRec'(endparen, Msg);
end MkEndparen;

-- selector functions

function TypeOfExp(E: Exp) return ExpType is
begin
  return E.etype;
end TypeOfExp;

function TypeOfFcn(E: Exp) return FcnType is
begin
  return E.funtype;
end TypeOfFcn;

function ConstVal(C : Exp) return Integer is
begin
  return C.value;
end ConstVal;

function VarName(Var : Exp) return Symbol is
begin
  return Var.vname;
end VarName;

function DefName(Defn : Exp) return Symbol is
begin
  return Defn.name;
end DefName;

function DefBody(Defn : Exp) return Exp is
begin
  return Defn.expr;
end DefBody;

function SetName(SetExp : Exp) return Symbol is
begin
  return SetExp.name;
end SetName;

function SetBody(SetExp : Exp) return Exp is
begin
  return SetExp.expr;
end SetBody;

function FcnName(Fcn : Exp) return Symbol is
begin
  return Fcn.fname;
end FcnName;

function FcnParams(Fcn : Exp) return SymbolList is
begin
  return Fcn.params;
end FcnParams;

function FcnBody(Fcn : Exp) return Exp is
begin
  return Fcn.fnbody;
end FcnBody;

function Seq(SeqExp : Exp) return ExpList is
begin
return SeqExp.list;
end Seq;

function AppOp(FunApp : Exp) return Exp is
begin
  return FunApp.op;
end AppOp;

function AppArgs(FunApp : Exp) return ExpList is
begin
 return FunApp.arglist;
end AppArgs;


-- tester functions

function IsConst(E : Exp) return Boolean is
begin
 return (E.etype = const);
end IsConst;

function IsVar(E : Exp) return Boolean is
begin
 return (E.etype = var);
end IsVar;

function IsDef(E : Exp) return Boolean is
begin
 return (E.etype = def);
end IsDef;

function IsSet(E : Exp) return Boolean is
begin
 return (E.etype = set);
end IsSet;

function IsFcn(E : Exp) return Boolean is
begin
 return (E.etype = fcn);
end IsFcn;

function IsSeq(E : Exp) return Boolean is
begin
 return (E.etype = seq);
end IsSeq;

function IsApp(E : Exp) return Boolean is
begin
 return (E.etype = app);
end IsApp;

function IsDummy(E : Exp) return Boolean is
begin
 return (E.etype = done);
end IsDummy;

function IsEndparen(E : Exp) return Boolean is
begin
 return (E.etype = endparen);
end IsEndparen;

end expr;