X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=XmlExpr.cs;h=7d6cec12fbe322b8e32a4fab7c56b925924f18c4;hb=1704d070aeebba69ffaa116451f5028adffb3095;hp=bfd48e7c64acf13ebf5e337b652986d22e939f14;hpb=c647f605517330db26cbabb4da77f152974feef8;p=m17n%2Fm17n-lib-cs.git

diff --git a/XmlExpr.cs b/XmlExpr.cs
index bfd48e7..7d6cec1 100644
--- a/XmlExpr.cs
+++ b/XmlExpr.cs
@@ -6,9 +6,17 @@ using System.Xml;
 
 namespace System.Xml.Expression
 {
-  public class Xex
+  public abstract class Xex
   {
-    public struct Name
+    public static bool Debug = false;
+
+    public static void DebugWrite (string fmt, params object[] arg)
+    {
+      if (Debug)
+	Console.Write (fmt, arg);
+    }
+
+    public struct Name : IEquatable<Name>
     {
       private static NameTable nt = new NameTable ();
 
@@ -19,31 +27,11 @@ namespace System.Xml.Expression
 	  name = nt.Add (str);
 	}
 
-      public Name (XmlAttribute attr)
-	{
-	  name = nt.Add (attr.Value);
-	}
-
-      public Name (XmlNode node)
-	{
-	  name = node.Name;
-	}
-
       public static implicit operator Name (string str)
       {
 	return new Name (str);
       }
 
-      public static implicit operator Name (XmlAttribute attr)
-      {
-	return new Name (attr);
-      }
-
-      public static implicit operator Name (XmlNode node)
-      {
-	return new Name (node);
-      }
-
       public static implicit operator string (Name name)
       {
 	return name.name;
@@ -54,24 +42,24 @@ namespace System.Xml.Expression
 	  return (object) n1.name == (object) n2.name;
 	}
 
-      public static bool operator== (Name n1, string n2)
+      public static bool operator!= (Name n1, Name n2)
 	{
-	  return (object) n1.name == (object) n2;
+	  return (object) n1.name != (object) n2.name;
 	}
 
-      public static bool operator== (string n1, Name n2)
+      public static bool operator== (Name n1, string n2)
 	{
-	  return (object) n1 == (object) n2.name;
+	  return (object) n1.name == (object) n2;
 	}
 
-      public static bool operator!= (Name n1, Name n2)
+      public static bool operator!= (Name n1, string n2)
 	{
-	  return (object) n1.name != (object) n2.name;
+	  return (object) n1.name != (object) n2;
 	}
 
-      public static bool operator!= (Name n1, string n2)
+      public static bool operator== (string n1, Name n2)
 	{
-	  return (object) n1.name != (object) n2;
+	  return (object) n1 == (object) n2.name;
 	}
 
       public static bool operator!= (string n1, Name n2)
@@ -79,10 +67,14 @@ namespace System.Xml.Expression
 	  return (object) n1 != (object) n2.name;
 	}
 
-      public override bool Equals (object other)
+      public bool Equals (Name name)
+      {
+	return Object.ReferenceEquals (this.name, name.name);
+      }
+
+      public override bool Equals (object obj)
       {
-	Console.WriteLine ("Equals (object)");
-	return Object.ReferenceEquals (this, other);
+	return Object.ReferenceEquals (this.name, obj);
       }
 
       public override int GetHashCode ()
@@ -91,8 +83,14 @@ namespace System.Xml.Expression
       }
 
       public static NameTable Table { get { return nt; } }
+
+      public override string ToString () { return name; }
     }
 
+    private static Name Nexpr = "expr";
+
+    private static Name Nfuncall = "funcall";
+    private static Name Nvariable = "variable";
     private static Name Ninteger = "integer";
     private static Name Nstring = "string";
     private static Name Nboolean = "boolean";
@@ -100,96 +98,193 @@ namespace System.Xml.Expression
     private static Name Nlist = "list";
     private static Name Nobject = "object";
 
-    private static Name Nconst = "const";
-    private static Name Nvariable = "varialbe";
+    private static Name Ndefun = "defun";
+    private static Name Nfname = "fname";
+    private static Name Nargs = "args";
+    private static Name Nargs_unevalled = "args-unevalled";
+    private static Name Noptional = "optional";
+    private static Name Nrest = "rest";
+    private static Name Nbody = "body";
+
+    private static Name Ndefvar = "defvar";
+    private static Name Ndescription = "description";
+    private static Name Nrange = "range";
 
-    private static Name Nfuncall = "funcall";
-    private static Name Nmname = "mname";
     private static Name Nprogn = "progn";
 
-    internal class Function
+    internal abstract class Function
     {
-      internal class Lambda
+      public Name name;
+      public int min_arg, max_arg;
+
+      public Function () { }
+
+      public Function (Name name, int min_arg, int max_arg)
       {
-	internal Name[] args;
-	internal Xex[] body;
+	this.name = name;
+	this.min_arg = min_arg;
+	this.max_arg = max_arg;
+      }
 
-	public Lambda (XmlNode node, Domain domain)
-	{
-	  Set (node, domain);
-	}
+      public abstract object Call (object[] args, Domain domain);
+
+      public override string ToString ()
+      {
+	return name;
+      }
 
-	public void Set (XmlNode node, Domain domain)
+      internal class Subroutine : Function
+      {
+	public Builtin builtin;
+
+	public Subroutine (Builtin builtin, Name name,
+			   int min_arg, int max_arg)
+	  : base (name, min_arg, max_arg)
+	  {
+	    this.builtin = builtin;
+	  }
+
+	public override object Call (object[] args, Domain domain)
 	{
-	  XmlNodeList body = node.ChildNodes;
-	  int idx = 0;
+	  object result;
 
-	  if (body[0].Name == "args")
+	  for (int i = 0; i < args.Length; i++)
 	    {
-	      XmlNodeList args = body[0].ChildNodes;
-	      if (this.args == null)
-		this.args = new Name[args.Count];
-	      for (int i = 0; i < args.Count; i++)
-		this.args[i] = args[i].InnerText;
-	      idx++;
+	      object val = ((Xex) args[i]).Eval (domain);
+	      if (val == null)
+		throw new Exception (args[i] + ":evaled to null");
+	      args[i] = val;
 	    }
-	  else if (this.args == null)
-	    this.args = new Name[0];
-	  if (this.body == null)
-	    this.body = new Xex[body.Count - idx];
-	  for (int i = 0; idx < body.Count; i++, idx++)
-	    this.body[i] = new Xex (body[idx], domain);
+	  DebugWrite ("calling (" + this);
+	  foreach (object a in args)
+	    DebugWrite (" " + a);
+	  DebugWrite (") => ");
+	  result = builtin (args, domain);
+	  DebugWrite (result + "\n");
+	  return result;
 	}
       }
 
-      public readonly Name name;
-      public Builtin builtin;
-      public int min_arg, max_arg;
-      internal Lambda lambda;
-      public bool specialp = false;
-
-      public Function (Name name, Builtin builtin,
-		       int min_arg, int max_arg, bool specialp)
+      internal class SpecialForm : Function
       {
-	this.name = name;
-	this.builtin = builtin;
-	this.min_arg = min_arg;
-	this.max_arg = max_arg;
-	this.specialp = specialp;
-      }
+	public Builtin builtin;
 
-      internal Function (Name name, XmlNode node, Domain domain)
-      {
-	this.name = name;
-	lambda = new Lambda (node, domain);
-	this.min_arg = this.max_arg = lambda.args.Length;
-      }
+	public SpecialForm (Builtin builtin, Name name,
+			    int min_arg, int max_arg)
+	  : base (name, min_arg, max_arg)
+	  {
+	    this.builtin = builtin;
+	  }
 
-      private Function ()
-      {
-	name = "nil";
+	public override object Call (object[] args, Domain domain)
+	{
+	  object result;
+
+	  DebugWrite ("calling (" + this);
+	  foreach (object a in args)
+	    DebugWrite (" " + a);
+	  DebugWrite (") => ");
+	  result = builtin (args, domain);
+	  DebugWrite (result + "\n");
+	  return result;
+	}
       }
 
-      public object Call (Xex[] args, Domain domain)
+      internal class Lambda : Function
       {
-	Bindings current = domain.bindings;
-	object result = false;
-
-	try {
-	  if (! specialp)
-	    foreach (Xex e in args)
-	      e.Eval (domain);
-	  if (builtin != null)
-	    return builtin (args, domain);
-	  if (lambda == null)
-	    return null;
-
-	  foreach (Xex e in lambda.body)
-	    result = e.Eval (domain);
-	} finally {
-	  domain.UnboundTo (current);
+	internal bool args_evalled;
+	internal Name[] args;
+	internal Xex[] body;
+
+	public Lambda (XmlNode node)
+	{
+	  int nargs = 0, noptions = 0, nrest = 0;
+	  name = node.Attributes[Nfname].Value;
+	    
+	  node = node.FirstChild;
+	  if (node != null
+	      && (node.Name == Nargs || node.Name == Nargs_unevalled))
+	    {
+	      XmlNode n;
+	      args_evalled = node.Name == Nargs;
+	      for (n = node.FirstChild; n != null; n = n.NextSibling)
+		{
+		  if (n.Name != Nsymbol)
+		    break;
+		  nargs++;
+		}
+	      if (n != null && n.Name == Noptional)
+		for (n = n.NextSibling; n != null; n = n.NextSibling)
+		  {
+		    if (n.Name == Nrest)
+		      break;
+		    noptions++;
+		  }
+	      if (n != null)
+		nrest++;
+	      min_arg = nargs;
+	      max_arg = nargs + noptions + nrest;
+	      if (nrest == 1)
+		max_arg = - max_arg;
+	      args = new Name[max_arg];
+	      n = node.FirstChild;
+	      for (int i = 0; i < max_arg; n = n.NextSibling)
+		if (n.Name == Nsymbol)
+		  args[i++] = n.InnerText;
+	    }
+	  else
+	    {
+	      min_arg = max_arg = 0;
+	    }
+	}
+
+	public void SetBody (XmlNode node, Domain domain)
+	{
+
+	  for (node = node.FirstChild; node != null && node.Name != Nbody;
+	       node = node.NextSibling);
+	  if (node != null)
+	    {
+	      XmlNodeList nlist = node.ChildNodes;
+
+	      body = new Xex[nlist.Count];
+	      for (int i = 0; i < nlist.Count; i++)
+		body[i] = New (nlist[i], domain);
+	    }
+	}
+
+	public override object Call (object[] args, Domain domain)
+	{
+	  Bindings current = domain.bindings;
+	  object result = false;
+
+	  try {
+	    int i;
+	    if (args_evalled)
+	      for (i = 0; i < min_arg; i++)
+		args[i] = ((Xex) args[i]).Eval (domain);
+	    for (i = 0; i < min_arg; i++)
+	      {
+		Variable var = domain.GetVar (this.args[i]);
+		domain.Bind (var, args[i]);
+	      }
+	    DebugWrite ("calling (" + this);
+	    foreach (Xex e in body)
+	      result = e.Eval (domain);
+	    DebugWrite (") => " + result + "\n");
+	  } finally {
+	    domain.UnboundTo (current);
+	  }
+	  return result;
+	}
+
+	public override string ToString ()
+	{
+	  string str = "(" + name;
+	  foreach (Name a in args)
+	    str += " " + a;
+	  return (str + ")");
 	}
-	return result;
       }
     }
 
@@ -201,9 +296,10 @@ namespace System.Xml.Expression
 
       public Variable (Name name, Name type, object value)
       {
+	if (value != null)
+	  Value = value;
 	this.name = name;
 	this.type = type;
-	val = value;
       }
 
       public object Value
@@ -212,14 +308,14 @@ namespace System.Xml.Expression
 	set
 	  {
 	    if (! ValueP (value))
-	      throw new Exception ("Invalid value type: " + value);
+	      throw new Exception ("Invalid value of " + name + ": " + value);
 	    val = value;
 	  }
       }
 
       public abstract bool ValueP (object value);
 
-      public override string ToString () { return name + "(" + type + ")"; }
+      public override string ToString () { return name + "=" + val; }
     }
 
     internal class VarInt : Variable
@@ -231,7 +327,7 @@ namespace System.Xml.Expression
 
       public Range[] ranges;
 
-      public VarInt (Name name, int value) : base (name, Ninteger, value) { }
+      public VarInt (Name name, object value) : base (name, Ninteger, value) { }
 
       public override bool ValueP (object value)
       {
@@ -253,7 +349,7 @@ namespace System.Xml.Expression
     {
       public string[] ranges;
 
-      public VarStr (Name name, string value) : base (name, Nstring, value) { }
+      public VarStr (Name name, object value) : base (name, Nstring, value) { }
 
       public override bool ValueP (object value)
       {
@@ -273,11 +369,14 @@ namespace System.Xml.Expression
 
     internal class VarBool : Variable
     {
-      public VarBool (Name name, bool value) : base (name, Nboolean, value) { }
+      public VarBool (Name name, object value)
+	: base (name, Nboolean, value) { }
 
       public override bool ValueP (object value)
       {
-	return value is bool;
+	if (! (value is bool))
+	  return false;
+	return true;
       }
     }
 
@@ -297,16 +396,16 @@ namespace System.Xml.Expression
       private object old_value;
       private Bindings next;
 	
-      private Bindings (Variable vari, object value)
+      private Bindings (Variable vari)
       {
 	this.vari = vari;
-	old_value = value;
+	old_value = vari.val;
       }
 	
       public static Bindings Bind (Bindings bindings,
 				   Variable vari, object value)
       {
-	Bindings b = new Bindings (vari, vari.val);
+	Bindings b = new Bindings (vari);
 
 	b.vari.Value = value;
 	b.next = bindings;
@@ -324,11 +423,12 @@ namespace System.Xml.Expression
       {
 	string str = "(bindings";
 	for (Bindings b = this; b != null; b = b.next)
-	  str += " " + vari;
+	  str += " " + vari.name + "=" + b.old_value;
 	return str + ")";
       }
     }
 
+#if false
     internal class ThrowException : Exception
     {
       Name tag;
@@ -340,87 +440,146 @@ namespace System.Xml.Expression
 	  this.value = value;
 	}
     }
+#endif
 
     public class Domain
     {
-      private Domain parent;
       public object context;
 
-      internal Dictionary<Name, Function> functions
-	= new Dictionary<Name, Function> ();
-      internal Dictionary<Name, Variable> variables
-	= new Dictionary<Name, Variable> ();
+      internal Dictionary<Name, Function> functions;
+      internal Dictionary<Name, Variable> variables;
       internal Bindings bindings;
 
-      internal Domain () { }
+      internal Domain ()
+      {
+	functions = new Dictionary<Name, Function> ();
+	variables = new Dictionary<Name, Variable> ();
+      }
 
-      public Domain (object context) : this (basic, context) { }
+      public Domain (object context) : this (basic, context)
+      {
+      }
 
       public Domain (Domain parent, object context)
       {
-	this.parent = parent;
+	functions = new Dictionary<Name, Function> (parent.functions);
+	variables = new Dictionary<Name, Variable> (parent.variables);
 	this.context = context;
       }
 
       internal void Bind (Variable vari, object value)
       {
 	bindings = Bindings.Bind (bindings, vari, value);
+	DebugWrite ("binding " + vari);
       }
 
       internal void UnboundTo (Bindings boundary)
       {
-	bindings = bindings.UnboundTo (boundary);
+	if (bindings != null)
+	  bindings = bindings.UnboundTo (boundary);
       }
 
-      public void Defun (Name name, Builtin builtin, int min_arg, int max_arg)
+      public void DefSubr (Builtin builtin, string str,
+			   int min_arg, int max_arg)
       {
-	Defun (name, builtin, min_arg, max_arg, false);
+	Name name = str;
+	functions[name]
+	  = new Function.Subroutine (builtin, name, min_arg, max_arg);
       }
 
-      public void Defun (Name name, Builtin builtin, int min_arg, int max_arg,
-			 bool specialp)
+      public void DefSpecial (Builtin builtin, string str,
+			      int min_arg, int max_arg)
       {
-	Function func;
+	Name name = str;
+	functions[name]
+	  = new Function.SpecialForm (builtin, name, min_arg, max_arg);
+      }
 
-	if (functions.TryGetValue (name, out func))
-	  {
-	    if (func.min_arg < min_arg || func.max_arg > max_arg)
-	      throw new Exception ("Incompatible argument numbers to override: "
-				   + name);
-	    func.builtin = builtin;
-	    func.lambda = null;
-	    func.min_arg = min_arg;
-	    func.max_arg = max_arg;
-	    func.specialp = specialp;
-	  }
-	else
-	  {
-	    functions[name]
-	      = new Function (name, builtin, min_arg, max_arg, specialp);
-	  }
+      internal Function.Lambda RegisterFunction (XmlNode node)
+      {
+	Function.Lambda lambda = new Function.Lambda (node);
+
+	functions[lambda.name] = lambda;	
+	return lambda;
       }
 
-      public void Defun (XmlNode node)
+      internal Function Defun (XmlNode node)
       {
-	Name name = node.Attributes["id"];
+	Name name = node.Attributes[Nfname].Value;
 	Function func;
 
-	if (functions.TryGetValue (name, out func))
+	if (! functions.TryGetValue (name, out func))
+	  func = RegisterFunction (node);
+	((Function.Lambda) func).SetBody (node, this);
+	return func;
+      }
+
+      public void Defvar (Name name, XmlNode node)
+      {
+	Variable vari;
+
+	if (node.Name == Ndescription)
+	  node = node.NextSibling;
+	if (node != null)
 	  {
-	    XmlNode args = node.FirstChild;
-	    int nargs = args.Name == "args" ? args.ChildNodes.Count : 0;
-
-	    if (func.min_arg < nargs || func.max_arg > nargs)
-	      throw new Exception ("Incompatible argument numbers to override: "
-				   + name);
-	    func.lambda.Set (node, this);
-	    func.builtin = null;
+	    Name type = node.Name;
+	    XmlNodeList range_list = null;
+	    int nranges = 0;
+	    string val = node.InnerText;
+
+	    node = node.NextSibling;
+	    if (node != null)
+	      {
+		range_list = node.ChildNodes;
+		nranges = range_list.Count;
+	      }
+
+	    if (type == Ninteger)
+	      {
+		VarInt vi = new VarInt (name, parse_integer (val));
+		if (range_list != null)
+		  {
+		    vi.ranges = new VarInt.Range[nranges];
+
+		    for (int i = 0; i < nranges; i++)
+		      {
+			XmlNode n = range_list[i];
+
+			if (n.Name == Nrange)
+			  {
+			    vi.ranges[i].from =
+			      parse_integer (n.FirstChild.InnerText);
+			    vi.ranges[i].to =
+			      parse_integer (n.LastChild.InnerText);
+			  }
+			else
+			  {
+			    int num = parse_integer (n.InnerText);
+			    vi.ranges[i].from = vi.ranges[i].to = num;
+			  }
+		      }
+		  }
+		vari = vi;
+	      }
+	    else if (type == Nstring)
+	      {
+		VarStr vs = new VarStr (name, val);
+		if (range_list != null)
+		  vs.ranges = new string[nranges];
+		for (int i = 0; i < nranges; i++)
+		  vs.ranges[i] = range_list[i].Value;
+		vari = vs;
+	      }
+	    else if (type == Nboolean)
+	      {
+		vari = new VarBool (name, val == "true");
+	      }
+	    else
+	      throw new Exception ("Unknown type: " + type);
 	  }
 	else
-	  {
-	    func = new Function (name, node, this);
-	    functions[name] = func;
-	  }	    
+	  vari = new VarMisc (name, null);
+	variables[name] = vari;
       }
 
       internal Function GetFunc (Name name)
@@ -428,11 +587,7 @@ namespace System.Xml.Expression
 	Function func;
 
 	if (! functions.TryGetValue (name, out func))
-	  {
-	    if (parent != null)
-	      return parent.GetFunc (name);
-	    throw new Exception ("Unknown function: " + name);
-	  }
+	  throw new Exception ("Unknown function: " + name);
 	return func;
       }
 
@@ -459,13 +614,6 @@ namespace System.Xml.Expression
 	return vari;
       }
 
-      internal Variable GetVar (Xex e)
-      {
-	if (! (e.val is Name))
-	  throw new Exception ("Not a symbol" + e.val);
-	return GetVar ((Name) e.val);
-      }
-
       public override string ToString ()
       {
 	string str = "<(functions";
@@ -474,7 +622,9 @@ namespace System.Xml.Expression
 	str += ") (variabls";
 	foreach (KeyValuePair<Name, Variable> kv in variables)
 	  str += " " + kv.Key;
-	str += " " + bindings;
+	str += ")";
+	if (bindings != null)
+	  str += " " + bindings;
 	if (context != null)
 	  str += " (" + context + ")";
 	str += ">";
@@ -482,7 +632,7 @@ namespace System.Xml.Expression
       }
     }
 
-    public delegate object Builtin (Xex[] args, Domain domain);
+    public delegate object Builtin (object[] args, Domain domain);
 
     private static Domain basic = new Domain ();
 
@@ -490,42 +640,68 @@ namespace System.Xml.Expression
 
     static Xex ()
     {
-      basic.Defun ("set", set_value, 2, 2, false);
-      basic.Defun ("=", set_value, 2, 2, false);
-      basic.Defun ("and", and, 1, -1, false);
-      basic.Defun ("&&", and, 1, -1, false);
-      basic.Defun ("or", or, 1, -1, false);
-      basic.Defun ("||", or, 1, -1, false);
-      basic.Defun ("not", not, 1, 1, false);
-      basic.Defun ("!", not, 1, 1, false);
-      basic.Defun ("+", add, 2, -1, false);
-      basic.Defun ("*", mul, 2, -1, false);
-      basic.Defun ("-", sub, 1, -1, false);
-      basic.Defun ("/", div, 2, -1, false);
-      basic.Defun ("%", mod, 2, 2, false);
-      basic.Defun ("|", logior, 2, -1, false);
-      basic.Defun ("&", logand, 2, -1, false);
-      basic.Defun ("+=", add_set, 2, -1, true);
-      basic.Defun ("*=", mul_set, 2, -1, true);
-      basic.Defun ("-=", sub_set, 2, -1, true);
-      basic.Defun ("/=", div_set, 2, -1, true);
-      basic.Defun ("%=", mod_set, 2, 2, true);
-      basic.Defun ("|=", logior_set, 2, -1, true);
-      basic.Defun ("&=", logand_set, 2, -1, true);
-      basic.Defun ("<<", lsh, 2, 2, false);
-      basic.Defun (">>", rsh, 2, 2, false);
-      basic.Defun ("<<=", lsh_set, 2, 2, true);
-      basic.Defun (">>=", rsh_set, 2, 2, true);
-      basic.Defun ("==", eq, 2, -1, false);
-      basic.Defun ("!=", noteq, 2, 2, false);
-      basic.Defun ("<", less_than, 2, -1, false);
-      basic.Defun ("<=", less_eq, 2, -1, false);
-      basic.Defun (">", greater_than, 2, -1, false);
-      basic.Defun (">=", greater_eq, 2, -1, false);
-      basic.Defun ("progn", progn_clause, 0, -1, true);
-      basic.Defun ("if", if_clause, 2, -1, true);
-      basic.Defun ("when", when_clause, 1, -1, true);
-      basic.Defun ("while", while_clause, 1, -1, true);
+      basic.DefSubr (set_value, "set", 2, 2);
+      basic.DefSubr (set_value, "=", 2, 2);
+      basic.DefSpecial (and, "and", 1, -1);
+      basic.DefSpecial (and, "&&", 1, -1);
+      basic.DefSpecial (or, "or", 1, -1);
+      basic.DefSpecial (or, "||", 1, -1);
+      basic.DefSubr (not, "not", 1, 1);
+      basic.DefSubr (not, "!", 1, 1);
+      basic.DefSubr (add, "add", 2, -1);
+      basic.DefSubr (add, "+", 2, -1);
+      basic.DefSubr (mul, "mul", 2, -1);
+      basic.DefSubr (mul, "*", 2, -1);
+      basic.DefSubr (sub, "sub", 1, -1);
+      basic.DefSubr (sub, "-", 1, -1);
+      basic.DefSubr (div, "div", 2, -1);
+      basic.DefSubr (div, "/", 2, -1);
+      basic.DefSubr (mod, "mod", 2, 2);
+      basic.DefSubr (mod, "%", 2, 2);
+      basic.DefSubr (logior, "logior", 2, -1);
+      basic.DefSubr (logior, "|", 2, -1);
+      basic.DefSubr (logand, "logand", 2, -1);
+      basic.DefSubr (logand, "&", 2, -1);
+      basic.DefSubr (add_set, "add-set", 2, -1);
+      basic.DefSubr (add_set, "+=", 2, -1);
+      basic.DefSubr (mul_set, "mul-set", 2, -1);
+      basic.DefSubr (mul_set, "*=", 2, -1);
+      basic.DefSubr (sub_set, "sub-set", 2, -1);
+      basic.DefSubr (sub_set, "-=", 2, -1);
+      basic.DefSubr (div_set, "div-set", 2, -1);
+      basic.DefSubr (div_set, "/=", 2, -1);
+      basic.DefSubr (mod_set, "mod-set", 2, 2);
+      basic.DefSubr (mod_set, "%=", 2, 2);
+      basic.DefSubr (logior_set, "logior-set", 2, -1);
+      basic.DefSubr (logior_set, "|=", 2, -1);
+      basic.DefSubr (logand_set, "logand-set", 2, -1);
+      basic.DefSubr (logand_set, "&=", 2, -1);
+      basic.DefSubr (lsh, "lsh", 2, 2);
+      basic.DefSubr (lsh, "<<", 2, 2);
+      basic.DefSubr (rsh, "rsh", 2, 2);
+      basic.DefSubr (rsh, ">>", 2, 2);
+      basic.DefSubr (lsh_set, "lsh-set", 2, 2);
+      basic.DefSubr (lsh_set, "<<=", 2, 2);
+      basic.DefSubr (rsh_set, "rsh-set", 2, 2);
+      basic.DefSubr (rsh_set, ">>=", 2, 2);
+      basic.DefSubr (eq, "eq", 2, -1);
+      basic.DefSubr (eq, "==", 2, -1);
+      basic.DefSubr (noteq, "noteq", 2, 2);
+      basic.DefSubr (noteq, "!=", 2, 2);
+      basic.DefSubr (less_than, "lt", 2, -1);
+      basic.DefSubr (less_than, "<", 2, -1);
+      basic.DefSubr (less_eq, "le", 2, -1);
+      basic.DefSubr (less_eq, "<=", 2, -1);
+      basic.DefSubr (greater_than, "gt", 2, -1);
+      basic.DefSubr (greater_than, ">", 2, -1);
+      basic.DefSubr (greater_eq, "ge", 2, -1);
+      basic.DefSubr (greater_eq, ">=", 2, -1);
+      basic.DefSubr (eval_clause, "eval", 1, 1);
+      basic.DefSpecial (progn_clause, "progn", 0, -1);
+      basic.DefSpecial (progn_clause, "expr", 0, -1);
+      basic.DefSpecial (if_clause, "if", 2, -1);
+      basic.DefSpecial (when_clause, "when", 1, -1);
+      basic.DefSpecial (while_clause, "while", 1, -1);
 
       Fprogn = basic.GetFunc (Nprogn);
     }
@@ -537,435 +713,396 @@ namespace System.Xml.Expression
 	      : true);
     }
 
-    private static object set_value (Xex[] args, Domain domain)
+    private static object set_value (object[] args, Domain domain)
     {
-      Variable vari = domain.GetVar (args[0]);
+      Variable vari = domain.GetVar ((Name) args[0]);
 
-      vari.Value = args[1].val;
+      vari.Value = args[1];
       return vari.val;
     }
 
-    private static object and (Xex[] args, Domain domain)
+    private static object and (object[] args, Domain domain)
     {
-      foreach (Xex arg in args)
-	if (! is_true (arg.val))
+      foreach (object arg in args)
+	if (! is_true (((Xex) arg).Eval (domain)))
 	  return false;
       return true;
     }
 
-    private static object or (Xex[] args, Domain domain)
+    private static object or (object[] args, Domain domain)
     {
-      foreach (Xex arg in args)
-	if (is_true (arg.val))
+      foreach (object arg in args)
+	if (is_true (((Xex) arg).Eval (domain)))
 	  return true;
       return false;
     }
 
-    private static object not (Xex[] args, Domain domain)
+    private static object not (object[] args, Domain domain)
     {
-      return ! is_true (args[0].val);
+      return ! is_true (args);
     }
 
-    private static object add (Xex[] args, Domain domain)
+    private static object add (object[] args, Domain domain)
     {
       int n = 0;
-      foreach (Xex e in args)
-	n += (int) e.val;
+      foreach (object arg in args)
+	n += (int) arg;
       return n;
     }
 
-      private static object mul (Xex[] args, Domain domain)
-      {
-	int n = 1;
-	foreach (Xex e in args)
-	  n *= (int) e.val;
-	return n;
-      }
-
-      private static object sub (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
-	if (args.Length == 1)
-	  return - n;
-	for (int i = 1; i < args.Length; i++)
-	  n -= (int) args[i].val;
-	return n;
-      }
+    private static object mul (object[] args, Domain domain)
+    {
+      int n = 1;
+      foreach (object arg in args)
+	n *= (int) arg;
+      return n;
+    }
 
-      private static object div (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
-	for (int i = 1; i < args.Length; i++)
-	  n /= (int) args[i].val;
-	return n;
-      }
+    private static object sub (object[] args, Domain domain)
+    {
+      int n = (int) args[0];
+      if (args.Length == 1)
+	return - n;
+      for (int i = 1; i < args.Length; i++)
+	n -= (int) args[i];
+      return n;
+    }
 
-      private static object mod (Xex[] args, Domain domain)
-      {
-	return ((int) args[0].val % (int) args[1].val);
-      }
+    private static object div (object[] args, Domain domain)
+    {
+      int n = (int) args[0];
+      for (int i = 1; i < args.Length; i++)
+	n /= (int) args[i];
+      return n;
+    }
 
-      private static object logior (Xex[] args, Domain domain)
-      {
-	int n = 0;
-	foreach (Xex e in args)
-	  n |= (int) e.val;
-	return n;
-      }
+    private static object mod (object[] args, Domain domain)
+    {
+      return ((int) args[0] % (int) args[1]);
+    }
 
-      private static object logand (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
-	for (int i = 1; i < args.Length; i++)
-	  n &= (int) args[i].val;
-	return n;
-      }
+    private static object logior (object[] args, Domain domain)
+    {
+      int n = 0;
+      foreach (object arg in args)
+	n |= (int) arg;
+      return n;
+    }
 
-      private static object add_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+    private static object logand (object[] args, Domain domain)
+    {
+      int n = (int) args[0];
+      for (int i = 1; i < args.Length; i++)
+	n &= (int) args[i];
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  n += (int) args[i].val;
-	vari.val = n;
-	return n;
-      }
+    private static object add_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object mul_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+      for (int i = 1; i < args.Length; i++)
+	n += (int) args[i];
+      vari.val = n;
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  n *= (int) args[i].val;
-	vari.val = n;
-	return n;
-      }
+    private static object mul_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object sub_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+      for (int i = 1; i < args.Length; i++)
+	n *= (int) args[i];
+      vari.val = n;
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  n -= (int) args[i].val;
-	vari.val = n;
-	return n;
-      }
+    private static object sub_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object div_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+      for (int i = 1; i < args.Length; i++)
+	n -= (int) args[i];
+      vari.val = n;
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  n /= (int) args[i].val;
-	vari.val = n;
-	return n;
-      }
+    private static object div_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object mod_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+      for (int i = 1; i < args.Length; i++)
+	n /= (int) args[i];
+      vari.val = n;
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  n %= (int) args[i].val;
-	vari.val = n;
-	return n;
-      }
+    private static object mod_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object logior_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+      for (int i = 1; i < args.Length; i++)
+	n %= (int) args[i];
+      vari.val = n;
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  n |= (int) args[i].val;
-	vari.val = n;
-	return n;
-      }
+    private static object logior_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object logand_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+      for (int i = 1; i < args.Length; i++)
+	n |= (int) args[i];
+      vari.val = n;
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  n &= (int) args[i].val;
-	vari.val = n;
-	return n;
-      }
+    private static object logand_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object lsh (Xex[] args, Domain domain)
-      {
-	return (int) args[0].val << (int) args[1].val;
-      }
+      for (int i = 1; i < args.Length; i++)
+	n &= (int) args[i];
+      vari.val = n;
+      return n;
+    }
 
-      private static object lsh_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+    private static object lsh (object[] args, Domain domain)
+    {
+      return (int) args[0] << (int) args[1];
+    }
 
-	n <<= (int) args[1].val;
-	vari.val = n;
-	return n;
-      }
+    private static object lsh_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object rsh (Xex[] args, Domain domain)
-      {
-	return (int) args[0].val >> (int) args[1].val;
-      }
+      n <<= (int) args[1];
+      vari.val = n;
+      return n;
+    }
 
-      private static object rsh_set (Xex[] args, Domain domain)
-      {
-	Variable vari = domain.GetVar (args[0]);
-	int n = (int) vari.val;
+    private static object rsh (object[] args, Domain domain)
+    {
+      return (int) args[0] >> (int) args[1];
+    }
 
-	n >>= (int) args[1].val;
-	vari.val = n;
-	return n;
-      }
+    private static object rsh_set (object[] args, Domain domain)
+    {
+      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      int n = (int) vari.val;
 
-      private static object eq (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
+      n >>= (int) args[1];
+      vari.val = n;
+      return n;
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  if (n != (int) args[i].val)
-	    return false;
-	return true;
-      }
+    private static object eq (object[] args, Domain domain)
+    {
+      object o = args[0];
 
-      private static object noteq (Xex[] args, Domain domain)
-      {
-	return ((int) args[0].val != (int) args[1].val);
-      }
+      for (int i = 1; i < args.Length; i++)
+	if (o != args[i])
+	  return false;
+      return true;
+    }
 
-      private static object less_than (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
+    private static object noteq (object[] args, Domain domain)
+    {
+      return (args[0] != args[1]);
+    }
 
-	for (int i = 1; i < args.Length; i++)
-	  {
-	    int n1 = (int) args[i].val;
-	    if (n >= n1)
-	      return false;
-	    n = n1;
-	  }
-	return true;
-      }
+    private static object less_than (object[] args, Domain domain)
+    {
+      int n = (int) args[0];
 
-      private static object less_eq (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
-	for (int i = 1; i < args.Length; i++)
-	  {
-	    int n1 = (int) args[i].val;
-	    if (n > n1)
-	      return false;
-	    n = n1;
-	  }
-	return true;
-      }
+      for (int i = 1; i < args.Length; i++)
+	{
+	  int n1 = (int) args[i];
+	  if (n >= n1)
+	    return false;
+	  n = n1;
+	}
+      return true;
+    }
 
-      private static object greater_than (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
-	for (int i = 1; i < args.Length; i++)
-	  {
-	    int n1 = (int) args[i].val;
-	    if (n <= n1)
-	      return false;
-	    n = n1;
-	  }
-	return true;
-      }
+    private static object less_eq (object[] args, Domain domain)
+    {
+      int n = (int) args[0];
+      for (int i = 1; i < args.Length; i++)
+	{
+	  int n1 = (int) args[i];
+	  if (n > n1)
+	    return false;
+	  n = n1;
+	}
+      return true;
+    }
 
-      private static object greater_eq (Xex[] args, Domain domain)
-      {
-	int n = (int) args[0].val;
-	for (int i = 1; i < args.Length; i++)
-	  {
-	    int n1 = (int) args[i].val;
-	    if (n < n1)
-	      return false;
-	    n = n1;
-	  }
-	return true;
-      }
+    private static object greater_than (object[] args, Domain domain)
+    {
+      int n = (int) args[0];
+      for (int i = 1; i < args.Length; i++)
+	{
+	  int n1 = (int) args[i];
+	  if (n <= n1)
+	    return false;
+	  n = n1;
+	}
+      return true;
+    }
 
-      private static object progn_clause (Xex[] args, Domain domain)
-      {
-	object result = true;
+    private static object greater_eq (object[] args, Domain domain)
+    {
+      int n = (int) args[0];
+      for (int i = 1; i < args.Length; i++)
+	{
+	  int n1 = (int) args[i];
+	  if (n < n1)
+	    return false;
+	  n = n1;
+	}
+      return true;
+    }
 
-	foreach (Xex e in args)
-	  result = e.Eval (domain);
-	return result;
-      }
+    private static object eval_clause (object[] args, Domain domain)
+    {
+      return ((Xex) args[0]).Eval (domain);
+    }
 
-      private static object if_clause (Xex[] args, Domain domain)
-      {
-	object result;
+    private static object progn_clause (object[] args, Domain domain)
+    {
+      object result = true;
 
-	if (is_true (args[0].Eval (domain)))
-	  result = args[1].Eval (domain);
-	else
-	  {
-	    result = false;
-	    for (int i = 2; i < args.Length; i++)
-	      result = args[i].Eval (domain);
-	  }
-	return result;
-      }
+      foreach (object arg in args)
+	result = ((Xex) arg).Eval (domain);
+      return result;
+    }
 
-      private static object when_clause (Xex[] args, Domain domain)
-      {
-	if (! is_true (args[0].Eval (domain)))
-	  return false;
+    private static object if_clause (object[] args, Domain domain)
+    {
+      object result;
 
-	object result = true;
-	for (int i = 1; i < args.Length; i++)
-	  result = args[i].Eval (domain);
-	return result;
-      }
+      if (is_true (((Xex) args[0]).Eval (domain)))
+	result = ((Xex) args[1]).Eval (domain);
+      else
+	{
+	  result = false;
+	  for (int i = 2; i < args.Length; i++)
+	    result = ((Xex) args[i]).Eval (domain);
+	}
+      return result;
+    }
 
-      private static object while_clause (Xex[] args, Domain domain)
-      {
-	while (is_true (args[0].Eval (domain)))
-	  for (int i = 1; i < args.Length; i++)
-	    args[i].Eval (domain);
+    private static object when_clause (object[] args, Domain domain)
+    {
+      if (! is_true (((Xex) args[0]).Eval (domain)))
 	return false;
-      }
-
-    // FUNCALL: function != null
-    // VARREF:  function == null, args[0] = DIRECT-SYMBOL
-    // DIRECT:  function == null, args == null
-
-    private Function function;
-    private Xex[] args;
-    private object val;
 
-    public Xex[] Args { get { return args; } }
-    public object Val { get { return val; } }
-
-    private Xex () { }
+      object result = true;
+      for (int i = 1; i < args.Length; i++)
+	result = ((Xex) args[i]).Eval (domain);
+      return result;
+    }
 
-    private Xex (object val)
+    private static object while_clause (object[] args, Domain domain)
     {
-      this.val = val;
+      while (is_true (((Xex) args[0]).Eval (domain)))
+	for (int i = 1; i < args.Length; i++)
+	  ((Xex) args[i]).Eval (domain);
+      return false;
     }
 
-    private static Xex macro_expand (Xex[] bindings, Name[] args, Xex e)
+    public abstract object Eval (Domain domain);
+    public abstract Name TypeOf { get; }
+
+    private class Funcall : Xex
     {
-      Xex xex;
+      internal Function func;
+      internal Xex[] args;
+      internal object[] real_args;
 
-      if (e.function != null)
-	{
-	  xex = new Xex ();
-	  xex.function = e.function;
-	  xex.args = new Xex[e.args.Length];
-	  for (int i = e.args.Length - 1; i >= 0; i--)
-	    xex.args[i] = macro_expand (bindings, args, e.args[i]);
-	}
-      else if (e.args != null)
-	{
-	  xex = new Xex ();
-	  Name name = (Name) e.args[0].val;
-	  for (int i = args.Length - 1; i >= 0; i--)
-	    if (args[i] == name)
-	      return bindings[i];
-	  xex.function = null;
-	  xex.args = new Xex[1];
-	  xex.args[0] = e.args[0];
-	}
-      else
+      public Funcall (Function func, Xex[] args)
 	{
-	  xex = e;
+	  this.func = func;
+	  this.args = args;
+	  real_args = new object[args.Length];
 	}
-      return xex;
+
+      public override object Eval (Domain domain)
+      {
+	for (int i = 0; i < args.Length; i++)
+	  real_args[i] = args[i];
+	return func.Call (real_args, domain);
+      }
+
+      public override Name TypeOf { get { return Nfuncall; } }
+
+      public override string ToString ()
+      {
+	string str = "(" + func.name;
+	if (args != null)
+	  foreach (Xex e in args)
+	    str += " " + e.ToString ();
+	return (str + ")");
+      }
     }
 
-    // EXPR = SYMBOL | MTEXT | INTEGER | FUNCALL | PROGN
-    // FUNCALL = '(' SYMBOL EXPR* ')'
-    // PROGN = '(' EXPR * ')'
-    public Xex (XmlNode node, Domain domain)
+    private class Varref : Xex
     {
-      Name name = node.Name;
+      internal Variable vari;
 
-      if (name == Nconst)
-	{
-	  Name type = node.Attributes["type"].Value;
-
-	  if (type == Ninteger)
-	    val = parse_integer (node.InnerText);
-	  else if (type == Nstring)
-	    val = node.InnerText;
-	  else if (type == Nsymbol)
-	    val = (Name) node.InnerText;
-	  else if (type == Nboolean)
-	    val = node.InnerText == "true";
-	  else if (type == Nlist)
-	    {
-	      List<Xex> list = new List<Xex> ();
-	      for (XmlNode n = node.FirstChild; n != null; n = n.NextSibling)
-		list.Add (new Xex (n, domain));
-	      val = list;
-	    }
-	  else
-	    throw new Exception ("Unknown type: " + type);
-	}
-      else if (name == Nvariable)
-	{
-	  args = new Xex[1];
-	  args[0] = new Xex (node.Attributes[0]);
-	}
-      else
-	{
-	  bool is_macro = false;
+      public Varref (Variable vari) { this.vari = vari; }
 
-	  if (name == Nfuncall)
-	    {
-	      name = node.Attributes[0].Value;
-	      if (Nmname == node.Attributes[0].Name)
-		is_macro = true;
-	    }
-	  function = domain.GetFunc (name);
+      public override object Eval (Domain domain)
+      {
+	return vari.val;
+      }
 
-	  XmlNodeList nlist = node.ChildNodes;
-	  int nargs = nlist.Count;
+      public override Name TypeOf { get { return Nvariable; } }
 
-	  if (nargs < function.min_arg
-	      || (function.max_arg >= 0 && nargs > function.max_arg))
-	    throw new Exception ("Invalid number of arguments to: "
-				 + name + " " + nargs);
-	  args = new Xex[nargs];
-	  for (int i = 0; i < nargs; i++)
-	    args[i] = new Xex (nlist[i]);
+      public override string ToString ()
+      {
+	return "$" + vari.name + "/" + vari.val;
+      }
+    }
 
-	  if (is_macro)
-	    {
-	      Function.Lambda lambda = function.lambda;
-	      Xex[] body = lambda.body;
-	      int len = body.Length;
-	      Xex[] newargs = new Xex[len];
-
-	      for (int i = 0; i < len; i++)
-		newargs[i] = macro_expand (args, lambda.args, body[i]);
-	      function = Fprogn;
-	      args = newargs;
-	    }
-	}
+    private class Const : Xex
+    {
+      public object val;
+
+      public Const (object val)	{ this.val = val; }
+
+      public override object Eval (Domain domain) { return val; }
+
+      public override Name TypeOf {
+	get
+	  {
+	    return (val is int ? Ninteger
+		    : val is string ? Nstring
+		    : val is bool ? Nboolean
+		    : val is Name ? Nsymbol
+		    : Nlist);
+	  }
+      }
+
+      public override string ToString () { return val.ToString (); }
     }
 
-    private int parse_integer (string str)
+    internal static int parse_integer (string str)
     {
       int len = str.Length;
       bool negative = false;
 
       if (len <= 1)
-	return (len == 0 ? 0 : str[0]);
+	return (len == 0 ? 0 : str[0] - '0');
 
       int c = str[0];
       int i;
@@ -979,7 +1116,7 @@ namespace System.Xml.Expression
 	      if (c < '0')
 		break;
 	      else if (c <= '9')
-		i = i * 16 + c;
+		i = i * 16 + (c - '0');
 	      else if (c < 'A')
 		break;
 	      else if (c <= 'F')
@@ -995,7 +1132,7 @@ namespace System.Xml.Expression
 	}
       if (c == '-')
 	negative = true;
-      i = c;
+      i = c - '0';
       for (int idx = 1; idx < len; idx++)
 	{
 	  c = str[idx];
@@ -1006,48 +1143,98 @@ namespace System.Xml.Expression
       return negative ? - i : i;
     }
 
-    public object Eval (Domain domain)
+    private static int pre_parse (XmlNodeList nlist, Domain domain)
     {
-      if (function == null)
+      int len = 0;
+      foreach (XmlNode node in nlist)
 	{
-	  if (args != null)
-	    {
-	      Variable vari = domain.GetVar ((Name) args[0].val);
-	      val = vari.val;
-	    }
-	  return val;
+	  if (node.Name == Ndefun)
+	    domain.RegisterFunction (node);
+	  else if (node.Name == Ndefvar)
+	    domain.Defvar ((Name) node.Attributes[0].Value, node.FirstChild);
+	  else
+	    len++;
+	}
+      return len;
+    }
+
+    private static void post_parse (XmlNodeList nlist, Xex[] args,
+				    Domain domain)
+    {
+      for (int i = 0, j = 0; i < nlist.Count; i++)
+	{
+	  XmlNode node = nlist[i];
+
+	  if (node.Name == Ndefun)
+	    domain.Defun (node);
+	  else if (node.Name != Ndefvar)
+	    args[j++] = New (node, domain);
 	}
-      else
-	val = function.Call (args, domain);
-      return val;
     }
 
-    public override string ToString ()
+    public static Xex New (string url, Domain domain)
     {
-      string str;
+      XmlDocument doc = new XmlDocument (Name.Table);
+      XmlNode node;
 
-      if (function != null)
+      using (XmlTextReader reader = new XmlTextReader (url, Name.Table))
 	{
-	  str = "(" + function.name;
-	  if (args != null)
-	    foreach (Xex e in args)
-	      str += " " + e.ToString ();
-	  str += ")";
+	  do {
+	    reader.Read ();
+	  } while (reader.NodeType != XmlNodeType.None
+		   && (reader.NodeType != XmlNodeType.Element
+		       || Nexpr != reader.Name));
+	  if (reader.NodeType == XmlNodeType.None)
+	    throw new Exception ("Node <expr> not found");
+	  node = doc.ReadNode (reader);
 	}
-      else if (args != null)
+
+      return New (node, domain);
+    }
+
+    public static Xex New (XmlNode node, Domain domain)
+    {
+      Name name = node.Name;
+      Xex xex;
+      if (name == Nvariable)
 	{
-	  str = (string) args[0].val;
+	  Variable vari = domain.GetVar ((Name) node.Attributes[0].Value);
+	  xex = new Xex.Varref (vari);
 	}
-      else if (val != null)
+      else if (name == Ninteger)
+	xex = new Xex.Const (parse_integer (node.InnerText));
+      else if (name == Nstring)
+	xex = new Xex.Const (node.InnerText);
+      else if (name == Nsymbol)
+	xex = new Xex.Const ((Name) node.InnerText);
+      else if (name == Nboolean)
+	xex = new Xex.Const (node.InnerText == "true");
+      else if (name == Nlist)
 	{
-	  if (val is string)
-	    str = "\"" + ((string) val) + "\"";
-	  else
-	    str = val.ToString ();
+	  List<Xex> list = new List<Xex> ();
+	  for (XmlNode n = node.FirstChild; n != null; n = n.NextSibling)
+	    list.Add (New (n, domain));
+	  xex = new Xex.Const (list);
 	}
       else
-	str = "()";
-      return str;
+	{
+	  if (name == Nfuncall)
+	    name = node.Attributes[0].Value;
+	  Function func = domain.GetFunc (name);
+
+	  XmlNodeList nlist = node.ChildNodes;
+	  int nargs = nlist.Count;
+
+	  if (nargs < func.min_arg
+	      || (func.max_arg >= 0 && nargs > func.max_arg))
+	    throw new Exception ("Invalid number of arguments to: "
+				 + name + " " + nargs);
+	  nargs =  pre_parse (nlist, domain);
+	  Xex[] args = new Xex[nargs];
+	  post_parse (nlist, args, domain);
+	  xex = new Xex.Funcall (func, args);
+	}
+      return xex;
     }
   }
 }