From 2071d76a521f876a44893bb3a3e7447c4ff1b0f9 Mon Sep 17 00:00:00 2001
From: handa <handa>
Date: Thu, 17 Sep 2009 08:54:28 +0000
Subject: [PATCH] *** empty log message ***

---
 XmlExpr.cs |  758 +++++++++++++++++++++++++++++++-----------------------------
 xex.cs     |    7 +-
 xex.txt    |    5 +-
 xex.xml    |   21 ++
 4 files changed, 423 insertions(+), 368 deletions(-)

diff --git a/XmlExpr.cs b/XmlExpr.cs
index 947d326..ee82b94 100644
--- a/XmlExpr.cs
+++ b/XmlExpr.cs
@@ -6,9 +6,9 @@ using System.Xml;
 
 namespace System.Xml.Expression
 {
-  public abstract class Xex
+  public class Xexpression
   {
-    public static bool Debug = false;
+    public static int debug_level = 0;
 
     public struct Name : IEquatable<Name>
     {
@@ -87,10 +87,8 @@ namespace System.Xml.Expression
     private static Name Nvariable = "variable";
     private static Name Ninteger = "integer";
     private static Name Nstring = "string";
-    private static Name Nboolean = "boolean";
     private static Name Nsymbol = "symbol";
     private static Name Nlist = "list";
-    private static Name Nobject = "object";
 
     private static Name Ndefun = "defun";
     private static Name Nfname = "fname";
@@ -120,7 +118,7 @@ namespace System.Xml.Expression
 	this.max_arg = max_arg;
       }
 
-      public abstract object Call (object[] args, Domain domain);
+      public abstract Term Call (Domain domain, Term[] args);
 
       public override string ToString ()
       {
@@ -138,21 +136,13 @@ namespace System.Xml.Expression
 	    this.builtin = builtin;
 	  }
 
-	public override object Call (object[] args, Domain domain)
+	public override Term Call (Domain domain, Term[] args)
 	{
-	  object result;
+	  Term[] newargs = new Term[args.Length];
 
 	  for (int i = 0; i < args.Length; i++)
-	    {
-	      object val = args[i];
-	      if (val is Xex)
-		val = ((Xex) val).Eval (domain);
-	      if (val == null)
-		throw new Exception (args[i] + ":evaled to null");
-	      args[i] = val;
-	    }
-	  result = builtin (args, domain);
-	  return result;
+	    newargs[i] = args[i].Eval (domain);
+	  return builtin (domain, newargs);
 	}
       }
 
@@ -167,17 +157,17 @@ namespace System.Xml.Expression
 	    this.builtin = builtin;
 	  }
 
-	public override object Call (object[] args, Domain domain)
+	public override Term Call (Domain domain, Term[] args)
 	{
-	  return builtin (args, domain);
+	  return builtin (domain, args);
 	}
       }
 
       internal class Lambda : Function
       {
 	internal bool args_evalled;
-	internal Name[] args;
-	internal Xex[] body;
+	internal Term[] args;
+	internal Term[] body;
 
 	public Lambda (XmlNode node)
 	{
@@ -207,13 +197,13 @@ namespace System.Xml.Expression
 		nrest++;
 	      min_arg = nargs;
 	      max_arg = nargs + noptions + nrest;
-	      if (nrest == 1)
-		max_arg = - max_arg;
-	      args = new Name[max_arg];
+	      args = new Term[max_arg];
 	      n = node.FirstChild;
 	      for (int i = 0; i < max_arg; n = n.NextSibling)
 		if (n.Name == Nsymbol)
-		  args[i++] = n.InnerText;
+		  args[i++] = new Term (n, null);
+	      if (nrest == 1)
+		max_arg = - max_arg;
 	    }
 	  else
 	    {
@@ -230,60 +220,54 @@ namespace System.Xml.Expression
 	    {
 	      XmlNodeList nlist = node.ChildNodes;
 
-	      body = new Xex[nlist.Count];
+	      body = new Term[nlist.Count];
 	      for (int i = 0; i < nlist.Count; i++)
-		body[i] = New (nlist[i], domain);
+		body[i] = new Term (nlist[i], domain);
 	    }
 	}
 
-	public override object Call (object[] args, Domain domain)
+	public override Term Call (Domain domain, Term[] args)
 	{
 	  Bindings current = domain.bindings;
-	  object result = false;
+	  Term result = Zero;
 
 	  try {
 	    int i;
 	    if (args_evalled)
-	      for (i = 0; i < min_arg; i++)
-		args[i] = ((Xex) args[i]).Eval (domain);
+	      {
+		Term[] newargs = new Term[args.Length];
+		for (i = 0; i < min_arg; i++)
+		  newargs[i] = args[i].Eval (domain);
+		args = newargs;
+	      }
 	    for (i = 0; i < min_arg; i++)
 	      {
-		Variable var = domain.GetVar (this.args[i]);
+		Variable var = domain.GetVar ((Name) this.args[i]);
 		domain.Bind (var, args[i]);
 	      }
-	    foreach (Xex e in body)
-	      result = e.Eval (domain);
+	    if (body != null)
+	      foreach (Term term in body)
+		result = term.Eval (domain);
 	  } finally {
 	    domain.UnboundTo (current);
 	  }
 	  return result;
 	}
-
-	public override string ToString ()
-	{
-	  string str = "(" + name;
-	  foreach (Name a in args)
-	    str += " " + a;
-	  return (str + ")");
-	}
       }
     }
 
     internal abstract class Variable
     {
       public readonly Name name;
-      public readonly Name type;
-      internal object val;
+      internal Term val;
 
-      public Variable (Name name, Name type, object value)
+      public Variable (Name name, Term term)
       {
-	if (value != null)
-	  Value = value;
 	this.name = name;
-	this.type = type;
+	Value = term;
       }
 
-      public object Value
+      public Term Value
       {
 	get { return val; }
 	set
@@ -294,87 +278,69 @@ namespace System.Xml.Expression
 	  }
       }
 
-      public abstract bool ValueP (object value);
+      public abstract bool ValueP (Term term);
 
       public override string ToString () { return name + "(" + val + ")"; }
-    }
 
-    internal class VarInt : Variable
-    {
-      public struct Range
+      internal class Int : Variable
       {
-	public int from, to;
-      }
+	public struct Range
+	{
+	  public int from, to;
+	}
 
-      public Range[] ranges;
+	public Range[] ranges;
 
-      public VarInt (Name name, object value) : base (name, Ninteger, value) { }
+	public Int (Name name, int i) : base (name, new Term (i)) { }
 
-      public override bool ValueP (object value)
-      {
-	int i;
+	public override bool ValueP (Term term)
+	{
+	  int i;
 
-	if (! (value is int))
-	  return false;
-	if (ranges == null)
-	  return true;
-	i = (int) value;
-	foreach (Range r in ranges)
-	  if (i >= r.from && i <= r.to)
+	  if (term.objval != null)
+	    return false;
+	  if (ranges == null)
 	    return true;
-	return false;
+	  i = term.intval;
+	  foreach (Range r in ranges)
+	    if (i >= r.from && i <= r.to)
+	      return true;
+	  return false;
+	}
       }
-    }
-
-    internal class VarStr : Variable
-    {
-      public string[] ranges;
-
-      public VarStr (Name name, object value) : base (name, Nstring, value) { }
 
-      public override bool ValueP (object value)
+      internal class Str : Variable
       {
-	string str;
-
-	if (! (value is string))
-	  return false;
-	if (ranges == null)
-	  return true;
-	str = (string) value;
-	foreach (string s in ranges)
-	  if (s == str)
-	    return true;
-	return false;
-      }
-    }
+	public string[] ranges;
 
-    internal class VarBool : Variable
-    {
-      public VarBool (Name name, object value)
-	: base (name, Nboolean, value) { }
+	public Str (Name name, string str) : base (name, new Term (str)) { }
 
-      public override bool ValueP (object value)
-      {
-	if (! (value is bool))
+	public override bool ValueP (Term term)
+	{
+	  if (! (term.objval is string))
+	    return false;
+	  if (ranges == null)
+	    return true;
+	  string str = (string) term.objval;
+	  foreach (string s in ranges)
+	    if (s == str)
+	      return true;
 	  return false;
-	return true;
+	}
       }
-    }
 
-    internal class VarMisc : Variable
-    {
-      public VarMisc (Name name, object value) : base (name, Nobject, value) { }
-
-      public override bool ValueP (object value)
+      internal class Misc : Variable
       {
-	return true;
+	public Misc (Name name, Term term) : base (name, term) { }
+
+	public override bool ValueP (Term term) { return true; }
       }
     }
 
     internal class Bindings
     {
       private Variable vari;
-      private object old_value;
+      private Term old_value;
       private Bindings next;
 	
       private Bindings (Variable vari)
@@ -383,12 +349,11 @@ namespace System.Xml.Expression
 	old_value = vari.val;
       }
 	
-      public static Bindings Bind (Bindings bindings,
-				   Variable vari, object value)
+      public static Bindings Bind (Bindings bindings, Variable vari, Term val)
       {
 	Bindings b = new Bindings (vari);
 
-	b.vari.Value = value;
+	b.vari.Value = val;
 	b.next = bindings;
 	return b;
       }
@@ -449,7 +414,7 @@ namespace System.Xml.Expression
 	this.context = context;
       }
 
-      internal void Bind (Variable vari, object value)
+      internal void Bind (Variable vari, Term value)
       {
 	bindings = Bindings.Bind (bindings, vari, value);
       }
@@ -495,10 +460,12 @@ namespace System.Xml.Expression
 	return func;
       }
 
-      public void Defvar (Name name, XmlNode node)
+      public void Defvar (XmlNode node)
       {
+	Name name = node.Attributes[0].Value;
 	Variable vari;
 
+	node = node.FirstChild;
 	if (node.Name == Ndescription)
 	  node = node.NextSibling;
 	if (node != null)
@@ -517,10 +484,10 @@ namespace System.Xml.Expression
 
 	    if (type == Ninteger)
 	      {
-		VarInt vi = new VarInt (name, parse_integer (val));
+		Variable.Int vi = new Variable.Int (name, parse_integer (val));
 		if (range_list != null)
 		  {
-		    vi.ranges = new VarInt.Range[nranges];
+		    vi.ranges = new Variable.Int.Range[nranges];
 
 		    for (int i = 0; i < nranges; i++)
 		      {
@@ -544,22 +511,18 @@ namespace System.Xml.Expression
 	      }
 	    else if (type == Nstring)
 	      {
-		VarStr vs = new VarStr (name, val);
+		Variable.Str vs = new Variable.Str (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
-	  vari = new VarMisc (name, null);
+	  vari = new Variable.Misc (name, Zero);
 	variables[name] = vari;
       }
 
@@ -591,7 +554,7 @@ namespace System.Xml.Expression
 	Variable vari;
 
 	if (! variables.TryGetValue (name, out vari))
-	  variables[name] = vari = new VarMisc (name, null);
+	  variables[name] = vari = new Variable.Misc (name, Zero);
 	return vari;
       }
 
@@ -612,9 +575,9 @@ namespace System.Xml.Expression
 	return str;
       }
 
-      public void DebugWrite (bool head, string fmt, params object[] arg)
+      public void DebugWrite (bool head, string fmt, params string[] arg)
       {
-	if (Debug)
+	if (debug_level > depth)
 	  {
 	    if (head)
 	      {
@@ -627,13 +590,13 @@ namespace System.Xml.Expression
       }
     }
 
-    public delegate object Builtin (object[] args, Domain domain);
+    public delegate Term Builtin (Domain domain, Term[] args);
 
     private static Domain basic = new Domain ();
 
     internal static Function Fprogn;
 
-    static Xex ()
+    static Xexpression ()
     {
       basic.DefSubr (set_value, "set", 2, 2);
       basic.DefSubr (set_value, "=", 2, 2);
@@ -691,6 +654,9 @@ namespace System.Xml.Expression
       basic.DefSubr (greater_than, ">", 2, -1);
       basic.DefSubr (greater_eq, "ge", 2, -1);
       basic.DefSubr (greater_eq, ">=", 2, -1);
+      basic.DefSubr (copy, "copy", 1, 1);
+      basic.DefSubr (append, "append", 1, -1);
+      basic.DefSpecial (quote_clause, "quote", 1, 1);
       basic.DefSubr (eval_clause, "eval", 1, 1);
       basic.DefSpecial (progn_clause, "progn", 0, -1);
       basic.DefSpecial (progn_clause, "expr", 0, -1);
@@ -701,14 +667,7 @@ namespace System.Xml.Expression
       Fprogn = basic.GetFunc (Nprogn);
     }
 
-    private static bool is_true (object val)
-    {
-      return (val is bool ? (bool) val
-	      : val is int ? (int) val == 0
-	      : true);
-    }
-
-    private static object set_value (object[] args, Domain domain)
+    private static Term set_value (Domain domain, Term[] args)
     {
       Variable vari = domain.GetVar ((Name) args[0]);
 
@@ -716,44 +675,44 @@ namespace System.Xml.Expression
       return vari.val;
     }
 
-    private static object and (object[] args, Domain domain)
+    private static Term and (Domain domain, Term[] args)
     {
-      foreach (object arg in args)
-	if (! is_true (((Xex) arg).Eval (domain)))
-	  return false;
-      return true;
+      foreach (Term arg in args)
+	if (! arg.Eval (domain).IsTrue)
+	  return Zero;
+      return One;
     }
 
-    private static object or (object[] args, Domain domain)
+    private static Term or (Domain domain, Term[] args)
     {
-      foreach (object arg in args)
-	if (is_true (((Xex) arg).Eval (domain)))
-	  return true;
-      return false;
+      foreach (Term arg in args)
+	if (arg.Eval (domain).IsTrue)
+	  return One;
+      return Zero;
     }
 
-    private static object not (object[] args, Domain domain)
+    private static Term not (Domain domain, Term[] args)
     {
-      return ! is_true (args);
+      return args[0].IsTrue ? Zero : One;
     }
 
-    private static object add (object[] args, Domain domain)
+    private static Term add (Domain domain, Term[] args)
     {
       int n = 0;
-      foreach (object arg in args)
+      foreach (Term arg in args)
 	n += (int) arg;
       return n;
     }
 
-    private static object mul (object[] args, Domain domain)
+    private static Term mul (Domain domain, Term[] args)
     {
       int n = 1;
-      foreach (object arg in args)
+      foreach (Term arg in args)
 	n *= (int) arg;
       return n;
     }
 
-    private static object sub (object[] args, Domain domain)
+    private static Term sub (Domain domain, Term[] args)
     {
       int n = (int) args[0];
       if (args.Length == 1)
@@ -763,7 +722,7 @@ namespace System.Xml.Expression
       return n;
     }
 
-    private static object div (object[] args, Domain domain)
+    private static Term div (Domain domain, Term[] args)
     {
       int n = (int) args[0];
       for (int i = 1; i < args.Length; i++)
@@ -771,20 +730,20 @@ namespace System.Xml.Expression
       return n;
     }
 
-    private static object mod (object[] args, Domain domain)
+    private static Term mod (Domain domain, Term[] args)
     {
       return ((int) args[0] % (int) args[1]);
     }
 
-    private static object logior (object[] args, Domain domain)
+    private static Term logior (Domain domain, Term[] args)
     {
       int n = 0;
-      foreach (object arg in args)
+      foreach (Term arg in args)
 	n |= (int) arg;
       return n;
     }
 
-    private static object logand (object[] args, Domain domain)
+    private static Term logand (Domain domain, Term[] args)
     {
       int n = (int) args[0];
       for (int i = 1; i < args.Length; i++)
@@ -792,129 +751,138 @@ namespace System.Xml.Expression
       return n;
     }
 
-    private static object add_set (object[] args, Domain domain)
+    private static Term add_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       for (int i = 1; i < args.Length; i++)
 	n += (int) args[i];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object mul_set (object[] args, Domain domain)
+    private static Term mul_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       for (int i = 1; i < args.Length; i++)
 	n *= (int) args[i];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object sub_set (object[] args, Domain domain)
+    private static Term sub_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       for (int i = 1; i < args.Length; i++)
 	n -= (int) args[i];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object div_set (object[] args, Domain domain)
+    private static Term div_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       for (int i = 1; i < args.Length; i++)
 	n /= (int) args[i];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object mod_set (object[] args, Domain domain)
+    private static Term mod_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       for (int i = 1; i < args.Length; i++)
 	n %= (int) args[i];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object logior_set (object[] args, Domain domain)
+    private static Term logior_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       for (int i = 1; i < args.Length; i++)
 	n |= (int) args[i];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object logand_set (object[] args, Domain domain)
+    private static Term logand_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       for (int i = 1; i < args.Length; i++)
 	n &= (int) args[i];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object lsh (object[] args, Domain domain)
+    private static Term lsh (Domain domain, Term[] args)
     {
       return (int) args[0] << (int) args[1];
     }
 
-    private static object lsh_set (object[] args, Domain domain)
+    private static Term lsh_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       n <<= (int) args[1];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object rsh (object[] args, Domain domain)
+    private static Term rsh (Domain domain, Term[] args)
     {
       return (int) args[0] >> (int) args[1];
     }
 
-    private static object rsh_set (object[] args, Domain domain)
+    private static Term rsh_set (Domain domain, Term[] args)
     {
-      Variable vari = domain.GetVar ((Name) ((Xex.Const) args[0]).val);
+      Variable vari = domain.GetVar ((Name) args[0]);
       int n = (int) vari.val;
 
       n >>= (int) args[1];
       vari.val = n;
-      return n;
+      return vari.val;
     }
 
-    private static object eq (object[] args, Domain domain)
+    private static Term eq (Domain domain, Term[] args)
     {
-      object o = args[0];
+      Term o = args[0];
 
-      for (int i = 1; i < args.Length; i++)
-	if (o != args[i])
-	  return false;
-      return true;
+      if (o.objval == null)
+	{
+	  for (int i = 1; i < args.Length; i++)
+	    if (args[i].objval != null || args[i].intval != o.intval)
+	      return Zero;
+	}
+      else
+	{
+	  for (int i = 1; i < args.Length; i++)
+	    if (o.objval.Equals (args[i].objval))
+	      return Zero;
+	}
+      return One;
     }
 
-    private static object noteq (object[] args, Domain domain)
+    private static Term noteq (Domain domain, Term[] args)
     {
-      return (args[0] != args[1]);
+      return eq (domain, args);
     }
 
-    private static object less_than (object[] args, Domain domain)
+    private static Term less_than (Domain domain, Term[] args)
     {
       int n = (int) args[0];
 
@@ -922,189 +890,293 @@ namespace System.Xml.Expression
 	{
 	  int n1 = (int) args[i];
 	  if (n >= n1)
-	    return false;
+	    return Zero;
 	  n = n1;
 	}
-      return true;
+      return One;
     }
 
-    private static object less_eq (object[] args, Domain domain)
+    private static Term less_eq (Domain domain, Term[] args)
     {
       int n = (int) args[0];
       for (int i = 1; i < args.Length; i++)
 	{
 	  int n1 = (int) args[i];
 	  if (n > n1)
-	    return false;
+	    return Zero;
 	  n = n1;
 	}
-      return true;
+      return One;
     }
 
-    private static object greater_than (object[] args, Domain domain)
+    private static Term greater_than (Domain domain, Term[] args)
     {
       int n = (int) args[0];
       for (int i = 1; i < args.Length; i++)
 	{
 	  int n1 = (int) args[i];
 	  if (n <= n1)
-	    return false;
+	    return Zero;
 	  n = n1;
 	}
-      return true;
+      return One;
     }
 
-    private static object greater_eq (object[] args, Domain domain)
+    private static Term greater_eq (Domain domain, Term[] args)
     {
       int n = (int) args[0];
       for (int i = 1; i < args.Length; i++)
 	{
 	  int n1 = (int) args[i];
 	  if (n < n1)
-	    return false;
+	    return Zero;
 	  n = n1;
 	}
-      return true;
+      return One;
+    }
+
+    private static Term copy (Domain domain, Term[] args)
+    {
+      object obj = args[0].objval;
+
+      if (! (obj is List<Term>))
+	throw new Exception ("Invalid arg to copy: " + args[0]);
+      return new Term (new List<Term> ((List<Term>) obj));
+    }
+
+    private static Term append (Domain domain, Term[] args)
+    {
+      object obj = args[0].objval;
+      if (obj is string)
+	{
+	  string str = "";
+	  foreach (Term arg in args)
+	    str += arg;
+	  return new Term (str);
+	}
+      else if (obj is List<Term>)
+	{
+	  List<Term> list = new List<Term> ();
+	  foreach (Term arg in args)
+	    list.AddRange ((List<Term>) arg.objval);
+	  return new Term (list);
+	}
+      throw new Exception ("Invalid term to append: " + obj);
+    }
+
+    private static Term quote_clause (Domain domain, Term[] args)
+    {
+      return new Term (args[0]);
     }
 
-    private static object eval_clause (object[] args, Domain domain)
+    private static Term eval_clause (Domain domain, Term[] args)
     {
-      return ((Xex) args[0]).Eval (domain);
+      return (args[0].Eval (domain));
     }
 
-    private static object progn_clause (object[] args, Domain domain)
+    private static Term progn_clause (Domain domain, Term[] args)
     {
-      object result = true;
+      Term result = One;
 
-      foreach (object arg in args)
-	result = ((Xex) arg).Eval (domain);
+      foreach (Term arg in args)
+	result = arg.Eval (domain);
       return result;
     }
 
-    private static object if_clause (object[] args, Domain domain)
+    private static Term if_clause (Domain domain, Term[] args)
     {
-      object result;
+      if (args[0].Eval (domain).IsTrue)
+	return args[1].Eval (domain);
 
-      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);
-	}
+      Term result = Zero;
+      for (int i = 2; i < args.Length; i++)
+	result = args[i].Eval (domain);
       return result;
     }
 
-    private static object when_clause (object[] args, Domain domain)
+    private static Term when_clause (Domain domain, Term[] args)
     {
-      if (! is_true (((Xex) args[0]).Eval (domain)))
-	return false;
+      if (! args[0].Eval (domain).IsTrue)
+	return Zero;
 
-      object result = true;
+      Term result = One;
       for (int i = 1; i < args.Length; i++)
-	result = ((Xex) args[i]).Eval (domain);
+	result = args[i].Eval (domain);
       return result;
     }
 
-    private static object while_clause (object[] args, Domain domain)
+    private static Term while_clause (Domain domain, Term[] args)
     {
-      while (is_true (((Xex) args[0]).Eval (domain)))
+      while (args[0].Eval (domain).IsTrue)
 	for (int i = 1; i < args.Length; i++)
-	  ((Xex) args[i]).Eval (domain);
-      return false;
+	  args[i].Eval (domain);
+      return Zero;
     }
 
-    public abstract object Eval (Domain domain);
-    public abstract Name TypeOf { get; }
-
-    private class Funcall : Xex
+    public struct Term
     {
-      internal Function func;
-      internal Xex[] args;
-      internal object[] real_args;
+      public int intval;
+      public object objval;
+
+      public Term (int i) { intval = i; objval = null; }
+      public Term (Name name) { intval = 0; objval = name; }
+      public Term (string str) { intval = 0; objval = str; }
+      public Term (List<Term> list) { intval = 0; objval = list; }
+      public Term (Term term) { intval = 0; objval = term; }
+
+      public Term (XmlNode node, Domain domain)
+	{
+	  Name name = node.Name;
 
-      public Funcall (Function func, Xex[] args)
+	  if (name == Ninteger)
+	    {
+	      intval = parse_integer (node.InnerText);
+	      objval = null;
+	    }
+	  else
+	    {
+	      intval = 0;
+	      if (name == Nsymbol)
+		objval = (Name) node.InnerText;
+	      else if (name == Nstring)
+		objval = node.InnerText.Clone ();
+	      else if (name == Nvariable)
+		objval = domain.GetVar ((Name) node.Attributes[0].Value);
+	      else if (name == Nlist)
+		{
+		  List<Term> list = new List<Term> ();
+		  for (node = node.FirstChild; node != null;
+		       node = node.NextSibling)
+		    list.Add (new Term (node, domain));
+		  objval = list;
+		}
+	      else
+		{
+		  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);
+		  Term[] args = new Term[nargs];
+		  for (int i = 0; i < nlist.Count; i++)
+		    args[i] = new Term (nlist[i], domain);
+		  objval = new Funcall (func, args);
+		}
+	    }
+	}
+
+      private class Funcall
+      {
+	internal Function func;
+	internal Term[] args;
+
+	public Funcall (Function func, Term[] args)
 	{
 	  this.func = func;
 	  this.args = args;
-	  real_args = new object[args.Length];
 	}
 
-      public override object Eval (Domain domain)
-      {
-	domain.DebugWrite (true, "(({0}", func);
-	for (int i = 0; i < args.Length; i++)
-	  {
-	    domain.DebugWrite (false, " {0}", args[i]);
-	    real_args[i] = args[i];
-	  }
-	domain.DebugWrite (false, ")");
-	domain.depth += 2;
-	object result = func.Call (real_args, domain);
-	domain.depth -= 2;
-	domain.DebugWrite (true, " => {0})", result);
-	return result;
+	public Term Eval (Domain domain)
+	{
+	  domain.DebugWrite (true, "(({0}", func.name);
+	  for (int i = 0; i < args.Length; i++)
+	    domain.DebugWrite (false, " {0}", args[i].ToString ());
+	  domain.DebugWrite (false, ")");
+	  domain.depth += 2;
+	  Term result = func.Call (domain, args);
+	  domain.depth -= 2;
+	  domain.DebugWrite (true, " => {0})", result.ToString ());
+	  return result;
+	}
+
+	public override string ToString ()
+	{
+	  string str = "<funcall fname=\"" + func.name;
+	  if (args == null)
+	    return str + "\"/>";
+	  str += "\">";
+	  foreach (Term e in args)
+	    str += e;
+	  return (str + "</funcall>");
+	}
       }
 
-      public override Name TypeOf { get { return Nfuncall; } }
+      public bool IsTrue {
+	get {
+	  return (objval == null
+		  ? (intval != 0)
+		  : objval is List<Term>
+		  ? (((List<Term>) objval).Count != 0)
+		  : true);
+	}
+      }
 
-      public override string ToString ()
+      public Term Eval (Domain domain)
       {
-	string str = "(" + func.name;
-	if (args != null)
-	  foreach (Xex e in args)
-	    str += " " + e.ToString ();
-	return (str + ")");
+	if (objval == null || objval is Name || objval is string)
+	  return this;
+	if (objval is List<Term>)
+	  return new Term ((List<Term>) objval);
+	if (objval is Funcall)
+	  return ((Funcall) objval).Eval (domain);
+	if (objval is Variable)
+	  return ((Variable) objval).val;
+	if (objval is Term)
+	  return (Term) objval;
+	throw new Exception ("invalid Term object: " + objval);
       }
-    }
-
-    private class Varref : Xex
-    {
-      internal Variable vari;
 
-      public Varref (Variable vari) { this.vari = vari; }
-
-      public override object Eval (Domain domain)
+      public static explicit operator int (Term term)
       {
-	domain.DebugWrite (true, "(get-value {0})", vari);
-	return vari.val;
+	if (term.objval != null)
+	  throw new Exception ("Not an integer term: " + term);
+	return term.intval;
       }
 
-      public override Name TypeOf { get { return Nvariable; } }
-
-      public override string ToString ()
+      public static explicit operator Name (Term term)
       {
-	return "$" + vari.name + "/" + vari.val;
+	return (Name) term.objval;
       }
-    }
-
-    private class Const : Xex
-    {
-      public object val;
-
-      public Const (object val)	{ this.val = val; }
 
-      public override object Eval (Domain domain)
+      public static implicit operator Term (int i)
       {
-	domain.DebugWrite (true, "(const {0})\n", val);
-	return val;
+	return new Term (i);
       }
 
-      public override Name TypeOf {
-	get
+      public override string ToString ()
+      {
+	if (objval == null)
+	  return "<integer>" + intval + "</integer>";
+	if (objval is Name)
+	  return "<symbol>" + objval + "</symbol>";
+	if (objval is string)
+	  return "<string>" + objval + "</string>";
+	if (objval is List<Term>)
 	  {
-	    return (val is int ? Ninteger
-		    : val is string ? Nstring
-		    : val is bool ? Nboolean
-		    : val is Name ? Nsymbol
-		    : Nlist);
+	    string str = "<list>";
+	    foreach (Term e in (List<Term>) objval)
+	      str += e;
+	    return str + "</list>";
 	  }
+	if (objval is Funcall)
+	  return "<funcall fname=\"" + ((Funcall) objval).func.name + "\"/>";
+	if (objval is Variable)
+	  return "<variable vname=\"" + ((Variable) objval).name + "\"/>";
+	if (objval is Term)
+	  return "<quote>" + objval + "</quote>";
+	throw new Exception ("invalid Term object: " + objval);
       }
-
-      public override string ToString () { return val.ToString (); }
     }
 
+    static Term Zero = new Term (0);
+    static Term One = new Term (1);
+
     internal static int parse_integer (string str)
     {
       int len = str.Length;
@@ -1152,36 +1224,9 @@ namespace System.Xml.Expression
       return negative ? - i : i;
     }
 
-    private static int pre_parse (XmlNodeList nlist, Domain domain)
-    {
-      int len = 0;
-      foreach (XmlNode node in nlist)
-	{
-	  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];
+    private Term[] terms;
 
-	  if (node.Name == Ndefun)
-	    domain.Defun (node);
-	  else if (node.Name != Ndefvar)
-	    args[j++] = New (node, domain);
-	}
-    }
-
-    public static Xex New (string url, Domain domain)
+    public Xexpression (string url, Domain domain)
     {
       XmlDocument doc = new XmlDocument (Name.Table);
       XmlNode node;
@@ -1192,58 +1237,47 @@ namespace System.Xml.Expression
 	    reader.Read ();
 	  } while (reader.NodeType != XmlNodeType.None
 		   && (reader.NodeType != XmlNodeType.Element
-		       || Nexpr != reader.Name));
+		       || reader.Name != Nexpr));
 	  if (reader.NodeType == XmlNodeType.None)
 	    throw new Exception ("Node <expr> not found");
 	  node = doc.ReadNode (reader);
 	}
 
-      return New (node, domain);
+      int nterms = 0;
+      for (XmlNode n = node.FirstChild; n != null; n = n.NextSibling)
+	if (n.NodeType == XmlNodeType.Element)
+	  {
+	    if (n.Name == Ndefun)
+	      domain.RegisterFunction (n);
+	    else if (n.Name == Ndefvar)
+	      domain.Defvar (n);
+	    else
+	      nterms++;
+	  }
+
+      terms = new Term[nterms];
+      int i = 0;
+      for (XmlNode n = node.FirstChild; n != null; n = n.NextSibling)
+	if (n.NodeType == XmlNodeType.Element)
+	  {
+	    if (n.Name == Ndefun)
+	      domain.Defun (n);
+	    else if (n.Name != Ndefvar)
+	      terms[i]= new Term (n, domain);
+	  }
     }
 
-    public static Xex New (XmlNode node, Domain domain)
+    public Term Eval (Domain domain)
     {
-      Name name = node.Name;
-      Xex xex;
-      if (name == Nvariable)
-	{
-	  Variable vari = domain.GetVar ((Name) node.Attributes[0].Value);
-	  xex = new Xex.Varref (vari);
-	}
-      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)
-	{
-	  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
+      Term result = Zero;
+
+      domain.depth = 0;
+      foreach (Term term in terms)
 	{
-	  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);
+	  result = term.Eval (domain);
+	  Console.WriteLine (result);
 	}
-      return xex;
+      return result;
     }
   }
 }
diff --git a/xex.cs b/xex.cs
index 2afa166..6b3a690 100644
--- a/xex.cs
+++ b/xex.cs
@@ -8,11 +8,10 @@ public class Test
 {
   public static void Main()
   {
-    Xex.Domain domain = new Xex.Domain (null);
-    Xex xex = Xex.New ("xex.xml", domain);
+    Xexpression.Domain domain = new Xexpression.Domain (null);
+    Xexpression xex = new Xexpression ("xex.xml", domain);
 
-    Xex.Debug = true;
+    Xexpression.debug_level = 1;
     Console.WriteLine (xex.Eval (domain));
-    Console.WriteLine (domain);
   }
 }
diff --git a/xex.txt b/xex.txt
index 575304f..950fa79 100644
--- a/xex.txt
+++ b/xex.txt
@@ -83,9 +83,10 @@ PREDEFINED-FUNC-SYMBOL =
   | 'add-set' | 'sub-set' | 'mul-set' | 'div-set' | 'mod-set'
   | 'logand' | 'logior' | 'logxor' | 'lsh'
   | 'logand-set' | 'logior-set' | 'logxor-set' | 'lsh-set'
-  | 'append' | 'concat' | 'substr'
   | 'tolist' | 'tostring'
-  | 'cons' | 'car' | 'cdr' | 'nth' | 'copy' | 'ins' | 'del'
+  | 'copy' | 'append'
+  | 'ins' | 'del'
+  | 'cons' | 'car' | 'cdr' | 'nth'
   | 'case' | 'cond' | 'if' | 'progn' | 'when'
   | 'while' | 'for' | 'foreach'
   | 'typeof'
diff --git a/xex.xml b/xex.xml
index 2a32d58..6efacdd 100644
--- a/xex.xml
+++ b/xex.xml
@@ -15,6 +15,27 @@
     </body>
   </defun>
 
+  <defun fname="temp">
+    <args-unevalled><symbol>x</symbol>
+      <optional/><symbol>y</symbol>
+      <rest/><symbol>rest</symbol>
+    </args-unevalled>
+    <body>
+      <list><variable vname="x"/></list>
+    </body>
+  </defun>
+
   <set><symbol>x</symbol><integer>10</integer></set>
   <funcall fname="factorial"><variable vname="x"/></funcall>
+  <append>
+    <funcall fname="temp">
+      <symbol>sym</symbol>
+      <symbol>sym</symbol>
+      <symbol>sym</symbol>
+    </funcall>
+    <list>
+      <integer>1</integer>
+    </list>
+    <list><integer>2</integer></list>
+  </append>
 </expr>
-- 
1.7.10.4