public virtual void Visit(SeqDisplayExpr sequenceDisplayExpression)
 {
     foreach (var element in sequenceDisplayExpression.Elements)
     {
         Visit(element);
     }
 }
        public string GenerateConditionString(SeqDisplayExpr expression, IDictionary <string, string> rename)
        {
            var bob = new StringBuilder();

            bob.Append("[");
            foreach (Expression element in expression.Elements)
            {
                bob.Append(GenerateConditionString(element, rename));
                bob.Append(", ");
            }

            if (expression.Elements.Count > 0)
            {
                bob.Remove(bob.Length - 2, 2);
            }
            bob.Append("]");
            return(bob.ToString());
        }
        public string GenerateString(SeqDisplayExpr expression)
        {
            var bob = new StringBuilder();

            bob.Append("[");
            foreach (Expression element in expression.Elements)
            {
                bob.Append(GenerateString(element));
                bob.Append(", ");
            }

            if (expression.Elements.Count > 0)
            {
                bob.Remove(bob.Length - 2, 2);
            }
            bob.Append("]");
            return(bob.ToString());
        }
Пример #4
0
        public override Expression GetStoreBufferLocation()
        {
            if (!AH.IsPrimitiveType(type))
            {
                return(null);
            }

            var fields = new List <Expression>();
            var v      = GetStoreBufferLocationInfo(ref fields);

            if (v == null)
            {
                return(null);
            }

            var fields_seq = new SeqDisplayExpr(Token.NoToken, fields);

            return(AH.MakeApply2("Armada_StoreBufferLocation_Unaddressable", v, fields_seq, "Armada_StoreBufferLocation"));
        }
Пример #5
0
 private static bool ShallowEq(SeqDisplayExpr expr1, SeqDisplayExpr expr2)
 {
     return(true);
 }
Пример #6
0
        void Suffix(ref Expression e)
        {
            Contract.Requires(e != null); Contract.Ensures(e!=null);
            IToken id, x;
            Expression e0 = null;  Expression e1 = null;  Expression ee;  bool anyDots = false;
            List<Expression> multipleLengths = null; bool takeRest = false; // takeRest is relevant only if multipleLengths is non-null
            List<Expression> multipleIndices = null;

            if (la.kind == 27) {
            DotSuffix(out id, out x);
            if (x != null) {
             // process id as a Suffix in its own right
             e = new ExprDotName(id, e, id.val, null);
             id = x;  // move to the next Suffix
            }
            IToken openParen = null;  List<Type> typeArgs = null;  List<Expression> args = null;

            if (IsGenericInstantiation()) {
                typeArgs = new List<Type>();
                GenericInstantiation(typeArgs);
            } else if (la.kind == 106) {
                HashCall(id, out openParen, out typeArgs, out args);
            } else if (StartOf(30)) {
            } else SynErr(225);
            e = new ExprDotName(id, e, id.val, typeArgs);
            if (openParen != null) {
             e = new ApplySuffix(openParen, e, args);
            }

            } else if (la.kind == 48) {
            Get();
            x = t;
            if (StartOf(7)) {
                Expression(out ee, true, true);
                e0 = ee;
                if (la.kind == 137) {
                    Get();
                    anyDots = true;
                    if (StartOf(7)) {
                        Expression(out ee, true, true);
                        e1 = ee;
                    }
                } else if (la.kind == 95) {
                    Get();
                    Expression(out ee, true, true);
                    e1 = ee;
                } else if (la.kind == 21) {
                    Get();
                    multipleLengths = new List<Expression>();
                    multipleLengths.Add(e0);  // account for the Expression read before the colon
                    takeRest = true;

                    if (StartOf(7)) {
                        Expression(out ee, true, true);
                        multipleLengths.Add(ee); takeRest = false;
                        while (IsNonFinalColon()) {
                            Expect(21);
                            Expression(out ee, true, true);
                            multipleLengths.Add(ee);
                        }
                        if (la.kind == 21) {
                            Get();
                            takeRest = true;
                        }
                    }
                } else if (la.kind == 22 || la.kind == 49) {
                    while (la.kind == 22) {
                        Get();
                        Expression(out ee, true, true);
                        if (multipleIndices == null) {
                         multipleIndices = new List<Expression>();
                         multipleIndices.Add(e0);
                        }
                        multipleIndices.Add(ee);

                    }
                } else SynErr(226);
            } else if (la.kind == 137) {
                Get();
                anyDots = true;
                if (StartOf(7)) {
                    Expression(out ee, true, true);
                    e1 = ee;
                }
            } else SynErr(227);
            if (multipleIndices != null) {
             e = new MultiSelectExpr(x, e, multipleIndices);
             // make sure an array class with this dimensionality exists
             var tmp = theBuiltIns.ArrayType(multipleIndices.Count, new IntType(), true);
            } else {
             if (!anyDots && e0 == null) {
               /* a parsing error occurred */
               e0 = dummyExpr;
             }
             Contract.Assert(anyDots || e0 != null);
             if (anyDots) {
               //Contract.Assert(e0 != null || e1 != null);
               e = new SeqSelectExpr(x, false, e, e0, e1);
             } else if (multipleLengths != null) {
               Expression prev = null;
               List<Expression> seqs = new List<Expression>();
                foreach (var len in multipleLengths) {
                  var end = prev == null ? len : new BinaryExpr(x, BinaryExpr.Opcode.Add, prev, len);
                  seqs.Add(new SeqSelectExpr(x, false, e, prev, end));
                  prev = end;
                }
               if (takeRest) {
                 seqs.Add(new SeqSelectExpr(x, false, e, prev, null));
               }
               e = new SeqDisplayExpr(x, seqs);
             } else if (e1 == null) {
               Contract.Assert(e0 != null);
               e = new SeqSelectExpr(x, true, e, e0, null);
             } else {
               Contract.Assert(e0 != null);
               e = new SeqUpdateExpr(x, e, e0, e1);
             }
            }

            Expect(49);
            } else if (la.kind == 50) {
            Get();
            IToken openParen = t; var args = new List<Expression>();
            if (StartOf(7)) {
                Expressions(args);
            }
            Expect(51);
            e = new ApplySuffix(openParen, e, args);
            } else SynErr(228);
        }
Пример #7
0
        void DisplayExpr(out Expression e)
        {
            Contract.Ensures(Contract.ValueAtReturn(out e) != null);
            IToken x;  List<Expression> elements;
            e = dummyExpr;

            if (la.kind == 46) {
            Get();
            x = t;  elements = new List<Expression/*!*/>();
            if (StartOf(7)) {
                Expressions(elements);
            }
            e = new SetDisplayExpr(x, true, elements);
            Expect(47);
            } else if (la.kind == 48) {
            Get();
            x = t;  elements = new List<Expression/*!*/>();
            if (StartOf(7)) {
                Expressions(elements);
            }
            e = new SeqDisplayExpr(x, elements);
            Expect(49);
            } else SynErr(232);
        }
Пример #8
0
        List <Expression> GenerateAutoReqs(Expression expr, Function parent)
        {
            List <Expression> reqs = new List <Expression>();
            Func <Expression, List <Expression> > generateAutoReqs = e => GenerateAutoReqs(e, parent);

            if (expr is LiteralExpr)
            {
            }
            else if (expr is ThisExpr)
            {
            }
            else if (expr is IdentifierExpr)
            {
            }
            else if (expr is SeqDisplayExpr)
            {
                SeqDisplayExpr e = (SeqDisplayExpr)expr;
                foreach (var elt in e.Elements)
                {
                    reqs.AddRange(generateAutoReqs(elt));
                }
            }
            else if (expr is FieldSelectExpr)
            {
                FieldSelectExpr e = (FieldSelectExpr)expr;
                reqs.AddRange(generateAutoReqs(e.Obj));
            }
            else if (expr is SeqSelectExpr)
            {
                SeqSelectExpr e = (SeqSelectExpr)expr;
                reqs.AddRange(generateAutoReqs(e.Seq));
                if (e.E0 != null)
                {
                    reqs.AddRange(generateAutoReqs(e.E0));
                }
                if (e.E1 != null)
                {
                    reqs.AddRange(generateAutoReqs(e.E1));
                }
            }
            else if (expr is SeqUpdateExpr)
            {
                SeqUpdateExpr e = (SeqUpdateExpr)expr;
                reqs.AddRange(generateAutoReqs(e.Seq));
                reqs.AddRange(generateAutoReqs(e.Index));
                reqs.AddRange(generateAutoReqs(e.Value));
            }
            else if (expr is FunctionCallExpr)
            {
                FunctionCallExpr e = (FunctionCallExpr)expr;
                foreach (var arg in e.Args)
                {
                    reqs.AddRange(generateAutoReqs(arg));
                }
                if (parent == null || parent.Name != e.name)
                {
                    ReqFunction(e.Function);
                    reqs.AddRange(GatherReqs(e.Function, e.Args));
                }
            }
            else if (expr is DatatypeValue)
            {
                DatatypeValue dtv = (DatatypeValue)expr;
                for (int i = 0; i < dtv.Arguments.Count; i++)
                {
                    Expression arg = dtv.Arguments[i];
                    reqs.AddRange(generateAutoReqs(arg));
                }
            }
            else if (expr is OldExpr)
            {
            }
            else if (expr is MatchExpr)
            {
                MatchExpr e = (MatchExpr)expr;
                reqs.AddRange(generateAutoReqs(e.Source));
                List <MatchCaseExpr> newMatches = new List <MatchCaseExpr>();
                foreach (MatchCaseExpr caseExpr in e.Cases)
                {
                    MatchCaseExpr c = new MatchCaseExpr(caseExpr.name, caseExpr.Arguments, Andify(generateAutoReqs(caseExpr.Body)));
                    newMatches.Add(c);
                }
                reqs.Add(new MatchExpr(e.Source, newMatches));
            }
            else if (expr is FreshExpr)
            {
            }
            else if (expr is UnaryExpr)
            {
                UnaryExpr  e   = (UnaryExpr)expr;
                Expression arg = e.E;
                reqs.AddRange(generateAutoReqs(arg));
            }
            else if (expr is BinaryExpr)
            {
                BinaryExpr e = (BinaryExpr)expr;
                switch (e.Op)
                {
                case BinaryExpr.Opcode.Imp:
                case BinaryExpr.Opcode.And:
                    reqs.AddRange(generateAutoReqs(e.E0));
                    foreach (var req in generateAutoReqs(e.E1))
                    {
                        reqs.Add(new BinaryExpr(Token.NoToken, BinaryExpr.Opcode.Imp, e.E0, req));
                    }
                    break;

                case BinaryExpr.Opcode.Or:
                    reqs.AddRange(generateAutoReqs(e.E0));
                    foreach (var req in generateAutoReqs(e.E1))
                    {
                        reqs.Add(new BinaryExpr(Token.NoToken, BinaryExpr.Opcode.Imp,
                                                new UnaryExpr(Token.NoToken, UnaryExpr.Opcode.Not, e.E0), req));
                    }
                    break;

                default:
                    reqs.AddRange(generateAutoReqs(e.E0));
                    reqs.AddRange(generateAutoReqs(e.E1));
                    break;
                }
            }
            else if (expr is LetExpr)
            {
                var e = (LetExpr)expr;
                if (e.Exact)
                {
                    foreach (var rhs in e.RHSs)
                    {
                        reqs.AddRange(generateAutoReqs(rhs));
                    }
                    var new_reqs = generateAutoReqs(e.Body);
                    if (new_reqs.Count > 0)
                    {
                        reqs.Add(new LetExpr(e.Exact, e.LHSs, e.RHSs, Andify(new_reqs)));
                    }
                }
            }
            else if (expr is QuantifierExpr)
            {
                QuantifierExpr e         = (QuantifierExpr)expr;
                var            auto_reqs = generateAutoReqs(e.Term);
                if (auto_reqs.Count > 0)
                {
                    Expression allReqsSatisfied        = Andify(auto_reqs);
                    Expression allReqsSatisfiedAndTerm = new BinaryExpr(Token.NoToken, BinaryExpr.Opcode.And, allReqsSatisfied, e.Term);
                    e.Term = allReqsSatisfiedAndTerm;
                }
            }
            else if (expr is StmtExpr)
            {
                var e = (StmtExpr)expr;
                reqs.AddRange(generateAutoReqs(e.E));
            }
            else if (expr is ITEExpr)
            {
                ITEExpr e = (ITEExpr)expr;
                reqs.AddRange(generateAutoReqs(e.Test));
                reqs.Add(new ITEExpr(e.Test, Andify(generateAutoReqs(e.Thn)), Andify(generateAutoReqs(e.Els))));
            }
            return(reqs);
        }
Пример #9
0
    public RtlExp GhostExpressionRec(Expression exp, bool inRecSpec = false, bool inRequiresOrOld = false)
    {
        Util.Assert(!isPrinting);
        exp = GetExp(exp);
        StmtExpr         stmtExpr    = exp as StmtExpr;
        IdentifierExpr   idExp       = exp as IdentifierExpr;
        LiteralExpr      literal     = exp as LiteralExpr;
        BinaryExpr       binary      = exp as BinaryExpr;
        UnaryExpr        unary       = exp as UnaryExpr;
        ITEExpr          ite         = exp as ITEExpr;
        ExistsExpr       existsExp   = exp as ExistsExpr;
        ForallExpr       forallExp   = exp as ForallExpr;
        LetExpr          letExp      = exp as LetExpr;
        MatchExpr        matchExp    = exp as MatchExpr;
        OldExpr          oldExp      = exp as OldExpr;
        FreshExpr        freshExp    = exp as FreshExpr;
        FunctionCallExpr funCall     = exp as FunctionCallExpr;
        DatatypeValue    dataVal     = exp as DatatypeValue;
        FieldSelectExpr  fieldSelect = exp as FieldSelectExpr;
        SeqSelectExpr    seqSelect   = exp as SeqSelectExpr;
        SeqUpdateExpr    seqUpdate   = exp as SeqUpdateExpr;
        SeqDisplayExpr   seqDisplay  = exp as SeqDisplayExpr;

        Func <Expression, RtlExp> G = e => GhostExpression(e, inRecSpec, inRequiresOrOld);

        if (stmtExpr != null)
        {
            if (stmtExprEnabled)
            {
                if (ignoreStmtExpr == 0)
                {
                    AddGhostStatement(stmtExpr.S);
                }
                return(G(stmtExpr.E));
            }
            else
            {
                throw new Exception("not implemented: cannot handle statement expression here");
            }
        }
        else if (idExp != null)
        {
            return(AsVar(idExp));
        }
        else if (literal != null && literal.Value is BigInteger)
        {
            return(new RtlInt((BigInteger)(literal.Value)));
        }
        else if (literal != null && literal.Value is bool)
        {
            return(new RtlLiteral((bool)(literal.Value) ? "true" : "false"));
        }
        else if (literal != null && literal.Value == null)
        {
            return(new RtlLiteral("ArrayOfInt(0 - 1, NO_ABS)"));
        }
        else if (literal != null && literal.Value is Microsoft.Basetypes.BigDec)
        {
            return(new RtlLiteral(((Microsoft.Basetypes.BigDec)literal.Value).ToDecimalString()));
        }
        else if (binary != null)
        {
            string          op              = null;
            string          internalOp      = null;
            CompileFunction compileFunction = this as CompileFunction;
            string          thisFuncName    = (compileFunction == null) ? null : compileFunction.function.Name;
            switch (binary.ResolvedOp)
            {
            case BinaryExpr.ResolvedOpcode.SeqEq:
                return(new RtlApply(dafnySpec.GetSeqOperationName(AppType(binary.E0.Type), "Seq_Equal"),
                                    new RtlExp[] { G(binary.E0), G(binary.E1) }));

            case BinaryExpr.ResolvedOpcode.SeqNeq:
                return(new RtlLiteral("(!" +
                                      new RtlApply(dafnySpec.GetSeqOperationName(AppType(binary.E0.Type), "Seq_Equal"),
                                                   new RtlExp[] { G(binary.E0), G(binary.E1) }) + ")"));

            case BinaryExpr.ResolvedOpcode.Concat:
                return(new RtlApply(dafnySpec.GetSeqOperationName(AppType(binary.Type), "Seq_Append"),
                                    new RtlExp[] { G(binary.E0), G(binary.E1) }));
            }
            if (binary.Op == BinaryExpr.Opcode.Exp)
            {
                binary = new BinaryExpr(binary.tok, BinaryExpr.Opcode.Imp, binary.E0, binary.E1);
            }
            switch (binary.Op)
            {
            case BinaryExpr.Opcode.Disjoint:
            case BinaryExpr.Opcode.In:
            case BinaryExpr.Opcode.NotIn:
                throw new Exception("not implemented: binary operator '" + BinaryExpr.OpcodeString(binary.Op) + "'");
            }
            if (AppType(binary.E0.Type) is IntType && AppType(binary.E1.Type) is IntType)
            {
                switch (binary.Op)
                {
                case BinaryExpr.Opcode.Le: internalOp = "INTERNAL_le_boogie"; break;

                case BinaryExpr.Opcode.Lt: internalOp = "INTERNAL_lt_boogie"; break;

                case BinaryExpr.Opcode.Ge: internalOp = "INTERNAL_ge_boogie"; break;

                case BinaryExpr.Opcode.Gt: internalOp = "INTERNAL_gt_boogie"; break;

                case BinaryExpr.Opcode.Add: internalOp = "INTERNAL_add_boogie"; break;

                case BinaryExpr.Opcode.Sub: internalOp = "INTERNAL_sub_boogie"; break;

                case BinaryExpr.Opcode.Mul:
                    op = "*";
                    if (thisFuncName != "INTERNAL_mul")
                    {
                        internalOp = FunName("INTERNAL__mul");
                    }
                    break;

                case BinaryExpr.Opcode.Div:
                    op = "div";
                    if (thisFuncName != "INTERNAL_div")
                    {
                        internalOp = FunName("INTERNAL__div");
                    }
                    break;

                case BinaryExpr.Opcode.Mod:
                    op = "mod";
                    if (thisFuncName != "INTERNAL_mod")
                    {
                        internalOp = FunName("INTERNAL__mod");
                    }
                    break;

                default:
                    op = BinaryExpr.OpcodeString(binary.Op);
                    break;
                }
            }
            else
            {
                op = BinaryExpr.OpcodeString(binary.Op);
            }
            if (internalOp == null)
            {
                return(new RtlBinary(op, G(binary.E0), G(binary.E1)));
            }
            else
            {
                return(new RtlApply(internalOp, new RtlExp[]
                                    { G(binary.E0), G(binary.E1) }));
            }
        }
        else if (unary != null && unary.Op == UnaryExpr.Opcode.Not)
        {
            return(new RtlLiteral("(!(" + G(unary.E) + "))"));
        }
        else if (unary != null && unary.Op == UnaryExpr.Opcode.SeqLength)
        {
            return(new RtlApply(dafnySpec.GetSeqOperationName(AppType(unary.E.Type), "Seq_Length"),
                                new RtlExp[] { G(unary.E) }));
        }
        else if (ite != null)
        {
            return(GhostIfThenElse(G(ite.Test), () => G(ite.Thn), () => G(ite.Els)));
        }
        else if (funCall != null)
        {
            switch (funCall.Function.Name)
            {
            case "left":
            case "right":
            case "relation":
            case "public":
                Util.Assert(funCall.Args.Count == 1);
                return(new RtlApply(funCall.Function.Name, new RtlExp[] { G(funCall.Args[0]) }));

            case "sizeof":
                Util.Assert(funCall.Args.Count == 1);
                return(new RtlApply(funCall.Function.Name + "##" + TypeString(AppType(funCall.Args[0].Type)),
                                    new RtlExp[] { G(funCall.Args[0]) }));

            case "INTERNAL_add_raw":
                Util.Assert(funCall.Args.Count == 2);
                return(new RtlBinary("+", G(funCall.Args[0]), G(funCall.Args[1])));

            case "INTERNAL_sub_raw":
                Util.Assert(funCall.Args.Count == 2);
                return(new RtlBinary("-", G(funCall.Args[0]), G(funCall.Args[1])));

            case "IntToReal":
                Util.Assert(funCall.Args.Count == 1);
                return(new RtlApply("real", new RtlExp[] { G(funCall.Args[0]) }));

            case "RealToInt":
                Util.Assert(funCall.Args.Count == 1);
                return(new RtlApply("int", new RtlExp[] { G(funCall.Args[0]) }));
            }
            TypeApply app = dafnySpec.Compile_Function(funCall.Function,
                                                       funCall.TypeArgumentSubstitutions.ToDictionary(p => p.Key, p => AppType(p.Value)));
            string        name     = FunName(SimpleName(app.AppName()));
            string        fullName = FunName(SimpleName(app.AppFullName()));
            List <RtlExp> rtlArgs  = funCall.Args.Select(G).ToList();
            List <RtlExp> rtlReads = funCall.Function.Reads.Where(e => e.Field != null).ToList()
                                     .ConvertAll(e => (RtlExp) new RtlVar(
                                                     GhostVar(e.FieldName), e.Field.IsGhost, AppType(e.Field.Type)));
            rtlArgs = rtlReads.Concat(rtlArgs).ToList();
            if (name.EndsWith("__INTERNAL__HEAP"))
            {
                name = name.Substring(0, name.Length - "__INTERNAL__HEAP".Length);
            }
            else if (DafnySpec.IsHeapFunction(funCall.Function))
            {
                rtlArgs.Insert(0, new RtlLiteral(inRequiresOrOld ? "$absMem_old" : "$absMem"));
            }
            if (Attributes.Contains(funCall.Function.Attributes, "opaque") &&
                funCall.Function.Formals.Count + rtlReads.Count == 0)
            {
                rtlArgs.Insert(0, new RtlLiteral("true"));
            }
            if (fullName == recFunName)
            {
                name = fullName;
            }
            if (name == recFunName)
            {
                recCalls.Add(new List <RtlExp>(rtlArgs));
                rtlArgs.Insert(0, new RtlApply("decreases_" + name, new List <RtlExp>(rtlArgs)));
                rtlArgs.Insert(1, new RtlLiteral(inRecSpec ? "__unroll" : "__unroll + 1"));
                name = "rec_" + name;
            }
            return(new RtlApply(name, rtlArgs));
        }
        else if (dataVal != null)
        {
            bool isSeq = dataVal.Type.TypeName(null).StartsWith("Seq<");
            return(new RtlApply((isSeq ? "_" : "") + dafnySpec.Compile_Constructor(
                                    dataVal.Type, dataVal.Ctor.Name, dataVal.InferredTypeArgs, typeApply.typeArgs).AppName(),
                                dataVal.Arguments.Select(G)));
        }
        else if (existsExp != null || forallExp != null)
        {
            QuantifierExpr qExp               = (QuantifierExpr)exp;
            bool           isForall           = forallExp != null;
            var            varTuples          = qExp.BoundVars.Select(v => Tuple.Create(GhostVar(v.Name), v.IsGhost, v.Type));
            var            oldRenamer         = PushRename(qExp.BoundVars.Select(v => v.Name));
            var            oldStmtExprEnabled = stmtExprEnabled;
            stmtExprEnabled = false;
            RtlExp rExp = new RtlLiteral((isForall ? "(forall " : "(exists ")
                                         + string.Join(", ", qExp.BoundVars.Select(v => GhostVar(v.Name) + ":" + TypeString(AppType(v.Type))))
                                         + " :: " + Triggers(qExp.Attributes, G) + " "
                                         + GetTypeWellFormedExp(varTuples.ToList(), isForall ? "==>" : "&&", G(qExp.Term)) + ")");
            stmtExprEnabled = oldStmtExprEnabled;
            PopRename(oldRenamer);
            return(rExp);
        }
        else if (letExp != null)
        {
            List <RtlExp> rhss;
            if (letExp.Exact)
            {
                rhss = letExp.RHSs.ConvertAll(e => G(e));
            }
            else if (letExp.LHSs.Count == 1 && LiteralExpr.IsTrue(letExp.RHSs[0]) && AppType(letExp.LHSs[0].Var.Type) is IntType)
            {
                rhss = new List <RtlExp> {
                    new RtlLiteral("0")
                };
            }
            else
            {
                throw new Exception("not implemented: LetExpr: " + letExp);
            }
            return(GhostLet(exp.tok, letExp.LHSs.ConvertAll(lhs => lhs.Var), rhss, () => G(letExp.Body)));
        }
        else if (matchExp != null)
        {
            if (matchExp.MissingCases.Count != 0)
            {
                throw new Exception("not implemented: MatchExpr with missing cases: " + matchExp);
            }
            //- match src case c1(ps1) => e1 ... cn(psn) => en
            //-   -->
            //- let x := src in
            //-   if x is c1 then let ps1 := ...x.f1... in e1 else
            //-   if x is c2 then let ps2 := ...x.f2... in e2 else
            //-                   let ps3 := ...x.f3... in e3
            var           src   = G(matchExp.Source);
            var           cases = matchExp.Cases;
            string        x     = TempName();
            Func <RtlExp> body  = null;
            for (int i = cases.Count; i > 0;)
            {
                i--;
                MatchCaseExpr         c     = cases[i];
                Func <List <RtlExp> > cRhss = () => c.Ctor.Formals.ConvertAll(f => (RtlExp) new RtlLiteral("("
                                                                                                           + f.Name + "#" + c.Ctor.Name + "(" + GhostVar(x) + "))"));
                Func <RtlExp> ec = () => GhostLet(exp.tok, c.Arguments, cRhss(), () => G(c.Body));
                if (body == null)
                {
                    body = ec;
                }
                else
                {
                    var prevBody = body;
                    body = () => GhostIfThenElse(new RtlLiteral("(" + GhostVar(x) + " is " + c.Ctor.Name + ")"),
                                                 ec, prevBody);
                }
            }
            return(GhostLet(exp.tok, new List <BoundVar> {
                new BoundVar(exp.tok, x, matchExp.Source.Type)
            },
                            new List <RtlExp> {
                src
            }, body));
        }
        else if (oldExp != null)
        {
            return(new RtlLiteral("old(" + GhostExpression(oldExp.E, inRecSpec, true) + ")"));
        }
        else if (freshExp != null)
        {
            Util.Assert(DafnySpec.IsArrayType(freshExp.E.Type));
            string abs = G(freshExp.E) + ".arrAbs";
            return(new RtlLiteral("(heap_old.absData[" + abs + "] is AbsNone)"));
        }
        else if (fieldSelect != null && fieldSelect.FieldName.EndsWith("?"))
        {
            string constructor = fieldSelect.FieldName.Substring(0, fieldSelect.FieldName.Length - 1);
            constructor = dafnySpec.Compile_Constructor(fieldSelect.Obj.Type, constructor, null, typeApply.typeArgs).AppName();
            bool isSeq = fieldSelect.Obj.Type.TypeName(null).StartsWith("Seq<");
            return(isSeq
                ? new RtlLiteral("is_" + constructor + "(" + G(fieldSelect.Obj) + ")")
                : new RtlLiteral("((" + G(fieldSelect.Obj) + ") is " + constructor + ")"));
        }
        else if (fieldSelect != null && !fieldSelect.Field.IsStatic && AppType(fieldSelect.Obj.Type) is UserDefinedType &&
                 fieldSelect.Field is DatatypeDestructor)
        {
            DatatypeDestructor field       = (DatatypeDestructor)fieldSelect.Field;
            string             constructor = dafnySpec.Compile_Constructor(fieldSelect.Obj.Type,
                                                                           field.EnclosingCtor.Name, null, typeApply.typeArgs).AppName();
            bool isSeq = fieldSelect.Obj.Type.TypeName(null).StartsWith("Seq<");
            return(new RtlLiteral("(" + fieldSelect.FieldName + (isSeq ? "_" : "#") + constructor
                                  + "(" + G(fieldSelect.Obj) + "))"));
        }
        else if (fieldSelect != null && DafnySpec.IsArrayType(AppType(fieldSelect.Obj.Type)) &&
                 fieldSelect.FieldName == "Length")
        {
            return(new RtlLiteral("(Arr_Length(" + G(fieldSelect.Obj) + "))"));
        }
        else if (fieldSelect != null && fieldSelect.Obj is ImplicitThisExpr)
        {
            //- we don't support objects yet, so interpret this as a global variable
            return(new RtlVar(GhostVar(fieldSelect.FieldName), true, fieldSelect.Type));
        }
        else if (seqSelect != null)
        {
            if (seqSelect.SelectOne && DafnySpec.IsArrayType(AppType(seqSelect.Seq.Type)))
            {
                return(new RtlExpComputed(e => "fun_INTERNAL__array__elems__index("
                                          + (inRequiresOrOld ? "$absMem_old" : "$absMem") + "[" + e.args[0] + ".arrAbs], ("
                                          + e.args[1] + "))", new RtlExp[] { G(seqSelect.Seq), G(seqSelect.E0) }));
            }
            else if (seqSelect.SelectOne)
            {
                return(new RtlApply(dafnySpec.GetSeqOperationName(AppType(seqSelect.Seq.Type), "Seq_Index"),
                                    new RtlExp[] { G(seqSelect.Seq), G(seqSelect.E0) }));
            }
            else
            {
                RtlExp seq = G(seqSelect.Seq);
                if (DafnySpec.IsArrayType(AppType(seqSelect.Seq.Type)))
                {
                    seq = new RtlApply(FunName("Seq__FromArray"), new RtlExp[] {
                        new RtlLiteral(inRequiresOrOld ? "$absMem_old" : "$absMem"), seq
                    });
                }
                if (seqSelect.E1 != null)
                {
                    seq = new RtlApply(dafnySpec.GetSeqOperationName(AppType(seqSelect.Type), "Seq_Take"),
                                       new RtlExp[] { seq, G(seqSelect.E1) });
                }
                if (seqSelect.E0 != null)
                {
                    seq = new RtlApply(dafnySpec.GetSeqOperationName(AppType(seqSelect.Type), "Seq_Drop"),
                                       new RtlExp[] { seq, G(seqSelect.E0) });
                }
                return(seq);
            }
        }
        else if (seqUpdate != null)
        {
            if (seqUpdate.ResolvedUpdateExpr != null)
            {
                return(GhostExpressionRec(seqUpdate.ResolvedUpdateExpr, inRecSpec, inRequiresOrOld));
            }
            return(new RtlApply(dafnySpec.GetSeqOperationName(AppType(seqUpdate.Seq.Type), "Seq_Update"),
                                new RtlExp[] { G(seqUpdate.Seq), G(seqUpdate.Index), G(seqUpdate.Value) }));
        }
        else if (seqDisplay != null)
        {
            RtlExp seq = new RtlApply(dafnySpec.GetSeqOperationName(AppType(seqDisplay.Type), "Seq_Empty"), new RtlExp[0]);
            foreach (Expression ei in seqDisplay.Elements)
            {
                seq = new RtlApply(dafnySpec.GetSeqOperationName(AppType(seqDisplay.Type), "Seq_Build"),
                                   new RtlExp[] { seq, G(ei) });
            }
            return(seq);
        }
        else
        {
            throw new Exception("not implemented: " + exp);
        }
    }