X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=MExpression.cs;h=d8fbadfce8bac430c1b78f3ac2f6ac324c754fe9;hb=4ab20c0f4785424513d93f02b82085e1394b3872;hp=959ea1dda966303b812cd2cc6e475b41b31c8a6c;hpb=0f6fd905d8745bc38a6e814f28f227b22de95fa0;p=m17n%2Fm17n-lib-cs.git

diff --git a/MExpression.cs b/MExpression.cs
index 959ea1d..d8fbadf 100644
--- a/MExpression.cs
+++ b/MExpression.cs
@@ -2,6 +2,8 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.IO;
+using System.Xml;
+
 using M17N;
 using M17N.Core;
 
@@ -9,791 +11,873 @@ namespace M17N.Core
 {
   public class MExpression
   {
-    public delegate object Evaluator (object[] args, MPlist bindings);
-
-    internal delegate void PrettyPrinter (Function func,
-					  string indent, object[] args);
+    private static MSymbol Mvarref = "symbol-value";
+    private static MSymbol Mdefun = "defun";
+    private static MSymbol Mcond = "cond";
+    private static MSymbol Mprogn = "progn";
+    private static MSymbol Mwhen = "when";
 
-    internal class Function
+    public class Domain
     {
-      internal readonly MSymbol name;
-      internal readonly Evaluator eval;
-      internal readonly int min_arg;
-      internal readonly int max_arg;
-      internal readonly Type[] arg_types;
-      internal object[] data;
+      private Domain parent;
+      internal MPlist functions = new MPlist ();
+      internal MPlist bindings = new MPlist ();
+      private Stack<MPlist> boundaries = new Stack<MPlist> ();
+      internal Translator translator;
+      public object context;
 
-      public PrettyPrinter pp;
+      internal Domain ()
+      {
+	boundaries.Push (bindings);
+      }
 
-      private static PrettyPrinter default_pretty_printer;
-      private static PrettyPrinter set_pretty_printer;
-      internal static Function literal, varref, block, defun;
+      public Domain (object context) : this (basic, context) { }
 
-      public Function (MSymbol name, Evaluator eval,
-		       int min_arg, int max_arg, params Type[] arg_types)
+      public Domain (Domain parent, object context)
       {
-	this.name = name;
-	this.eval = eval;
-	this.min_arg = min_arg;
-	this.max_arg = max_arg;
-	this.arg_types = (Type []) arg_types.Clone ();
-	if (arg_types.Length == 2 && arg_types[0] == typeof (MSymbol))
-	  pp = set_pretty_printer;
+	this.parent = parent;
+	this.context = context;
+	boundaries.Push (bindings);
+      }
+
+      public void AddTranslator (Translator translator)
+      {
+	if (this.translator == null)
+	  this.translator = translator;
 	else
-	  pp = default_pretty_printer;
+	  this.translator += translator;
       }
 
-      static Function ()
+      public void Bind (MSymbol sym, object value)
       {
-	default_pretty_printer = new PrettyPrinter (default_pp);
-	set_pretty_printer = new PrettyPrinter (set_pp);
-	literal = Defun ("nil", null, 1, 1);
-	varref = Defun ("symbol", new Evaluator (get_value), 1, 1);
-	block = Defun ("plist", new Evaluator (progn), 1, -1);
-
-	Defun ("set", new Evaluator (set_value), 2, 2,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("=", new Evaluator (set_value), 2, 2,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("+", new Evaluator (plus), 1, -1);
-	Defun ("*", new Evaluator (multi), 2, -1);
-	Defun ("-", new Evaluator (minus), 1, -1);
-	Defun ("/", new Evaluator (divide), 2, -1);
-	Defun ("%", new Evaluator (percent), 2, -1);
-	Defun ("|", new Evaluator (logior), 2, -1);
-	Defun ("&", new Evaluator (logand), 2, -1);
-	Defun ("+=", new Evaluator (pluseq), 2, -1,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("*=", new Evaluator (multieq), 2, -1,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("-=", new Evaluator (minuseq), 2, -1,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("/=", new Evaluator (divideeq), 2, -1,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("%=", new Evaluator (percenteq), 2, -1,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("|=", new Evaluator (logioreq), 2, -1,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("&=", new Evaluator (logandeq), 2, -1,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("<<", new Evaluator (lshift), 2, 2);
-	Defun (">>", new Evaluator (rshift), 2, 2);
-	Defun ("<<=", new Evaluator (lshifteq), 2, 2,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun (">>=", new Evaluator (rshifteq), 2, 2,
-	       typeof (MSymbol), typeof (MExpression));
-	Defun ("==", new Evaluator (eq), 2, -1);
-	Defun ("!=", new Evaluator (noteq), 2, 2);
-	Defun ("<", new Evaluator (less), 2, -1);
-	Defun ("<=", new Evaluator (lesseq), 2, -1);
-	Defun (">", new Evaluator (more), 2, -1);
-	Defun (">=", new Evaluator (moreeq), 2, -1);
-	block = Defun ("progn", new Evaluator (progn), 1, -1);
-	block.pp = new PrettyPrinter (block_pp);
-	Defun ("cond", new Evaluator (cond), 1, -1,
-	       typeof (MExpression[])).pp = new PrettyPrinter (cond_pp);
-	Defun ("if", new Evaluator (ifclause), 2, -1,
-	       typeof (MExpression)).pp = new PrettyPrinter (if_pp);
-	Defun ("while", new Evaluator (whileclause), 1, -1,
-	       typeof (MExpression)).pp = new PrettyPrinter (while_pp);
-	defun = Defun ("defun", new Evaluator (define_function), 4, -1,
-		       typeof (FunctionTable),
-		       typeof (MSymbol),
-		       typeof (MPlist),
-		       typeof (MExpression));
-	defun.pp = new PrettyPrinter (defun_pp);
-      }
-
-      private static MPlist find_binding (object[] args, MPlist bindings)
-      {
-	MSymbol var = (MSymbol) args[0];
-	MPlist slot = bindings.Find (var);
+	bindings = bindings.Cons (sym, value);
+      }
 
-	if (slot == null)
-	  throw new Exception ("Unbound variable: " + var);
-	return slot;
+      public MPlist SetBoundary ()
+      {
+	boundaries.Push (bindings);
+	return bindings;
       }
 
-      public object Call (object[] args, MPlist bindings)
+      public void UnboundTo (MPlist boundary)
       {
-	if (name == MSymbol.nil)
-	  return args[0];
-	if (eval != null)
-	  return eval (args, bindings);
+	while (boundary != boundaries.Pop ());
+	while (bindings != boundary)
+	  bindings = bindings.next;
+      }
 
-	MPlist arg_symbols = (MPlist) data[0];
-	for (int i = 0; i < args.Length; i++, arg_symbols = arg_symbols.next)
-	  bindings = bindings.Cons (arg_symbols.Symbol,
-				    ((MExpression) args[i]).Eval (bindings));
-	object result = 0;
-	for (int i = 1; i < data.Length; i++)
-	  result = ((MExpression) data[i]).Eval (bindings);
-	return result;
+      public void Defun (string name, Builtin builtin, int min_arg, int max_arg)
+      {
+	Defun (name, builtin, min_arg, max_arg, false);
       }
 
-      // Commonly used pretty-printers.
+      public void Defun (string name, Builtin builtin, int min_arg, int max_arg,
+			 bool specialp)
+      {
+	MSymbol sym = name;
+	Function func = (Function) functions.Get (sym);
 
-      public static void default_pp (Function func,
-				     string indent, object[] args)
+	if (func != null)
+	  {
+	    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
+	  {
+	    func = new Function (sym, builtin, min_arg, max_arg, specialp);
+	    functions = functions.Cons (sym, func);
+	  }
+      }
+
+      public void Defun (MSymbol sym, MPlist args, MPlist body)
       {
-	Console.Write ("(" + func.name);
-	indent += "  ";
-	foreach (MExpression o in args)
+	Function func = (Function) functions.Get (sym);
+
+	if (func != null)
 	  {
-	    Console.Write (" ");
-	    o.pp (indent);
+	    int nargs = args == null ? 0 : args.Count;
+
+	    if (func.min_arg < nargs || func.max_arg > nargs)
+	      throw new Exception ("Incompatible argument numbers to override: "
+				   + sym);
+	    func.lambda.SetArgs (args);
+	    func.lambda.SetBody (body, this);
+	    func.builtin = null;
 	  }
-	Console.Write (")");
+	else
+	  {
+	    func = new Function (sym, args, body, this);
+	    functions = functions.Cons (sym, func);
+	  }	    
       }
 
-      private static void set_pp (Function func, string indent, object[] args)
+      public void Defun (XmlNode node)
       {
-	Console.Write ("(" + func.name + " " + (MSymbol) args[0] + " ");
-	((MExpression) args[1]).pp (indent);
-	Console.Write (")");
+	MSymbol sym = node.Attributes["id"].Value;
+	Function func = (Function) functions.Get (sym);
+
+	if (func != 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: "
+				   + sym);
+	    func.lambda.Set (node, this);
+	    func.builtin = null;
+	  }
+	else
+	  {
+	    func = new Function (sym, node, this);
+	    functions = functions.Cons (sym, func);
+	  }	    
       }
 
-      private static object get_value (object[] args, MPlist bindings)
+      internal Function GetFunc (MSymbol name)
       {
-	return find_binding (args, bindings).val;
+	Function func = (Function) functions.Get (name);
+
+	if (func == null)
+	  {
+	    if (parent != null)
+	      return parent.GetFunc (name);
+	    throw new Exception ("Unknown function: " + name);
+	  }
+	return func;
       }
 
-      private static object set_value (object[] args, MPlist bindings)
+      public bool CopyFunc (Domain domain, MSymbol name)
       {
-	MSymbol var = (MSymbol) args[0];
-	MPlist slot = bindings.Find (var);
+	Function func = (Function) functions.Get (name);
+	if (func == null)
+	  return false;
+	domain.functions = domain.functions.Cons (name, func);
+	return true;
+      }
 
-	if (slot == null)
-	  slot = bindings.Push (var, null);
-	slot.val = ((MExpression) args[1]).Eval (bindings);
-	if (slot.val is MText)
-	  slot.val = ((MText) slot.val).Dup ();
-	return slot.val;
+      public void CopyFunc (Domain domain)
+      {
+	foreach (MPlist p in functions)
+	  domain.functions = domain.functions.Cons (p.key, p.val);
       }
 
-      private static object plus (object[] args, MPlist bindings)
+      public object GetValue (MSymbol name)
       {
-	object val = ((MExpression) args[0]).Eval (bindings);
+	MPlist slot = bindings.Find (name);
 
-	if (val is int)
+	if (slot == null)
 	  {
-	    int n = 0;
-	    foreach (MExpression e in args)
-	      n += (int) e.Eval (bindings);
-	    val = n;
+	    if (parent != null)
+	      return parent.GetValue (name);
+	    throw new Exception ("Unbound variable: " + name);
 	  }
-	else if (val is MText)
+	return slot.val;
+      }
+
+      public object SetValue (MSymbol name, object val)
+      {
+	MPlist boundary = boundaries.Peek ();
+
+	for (MPlist plist = bindings; plist != boundary; plist = plist.next)
+	  if (plist.key == name)
+	    {
+	      plist.val = val;
+	      return val;
+	    }
+	bindings = bindings.Cons (name, val);
+	return val;
+      }
+
+      public bool IsBound (MSymbol name)
+      {
+	return (bindings.Find (name) != null);
+      }
+
+      public void Translate (MPlist plist)
+      {
+	if (parent != null)
+	  parent.Translate (plist);
+	if (translator != null)
+	  for (MPlist p = plist; ! p.IsEmpty; p = p.next)
+	    translator (p, this);
+      }
+
+      public override string ToString ()
+      {
+	string str = "<(functions";
+	foreach (MPlist p in functions)
+	  str += " " + p.key;
+	str += ") (bindings " + bindings + ")";
+	if (context != null)
+	  str += " (" + context + ")";
+	str += ">";
+	return str;
+      }
+    }
+
+    public delegate object Builtin (MExpression[] args, Domain domain);
+    public delegate void Translator (MPlist plist, Domain domain);
+
+    internal class Function
+    {
+      internal class Lambda
+      {
+	internal MSymbol[] args;
+	internal MExpression[] body;
+
+	public Lambda (MPlist args, MPlist body, Domain domain)
+	{
+	  SetArgs (args);
+	  SetBody (body, domain);
+	}
+
+	public Lambda (XmlNode node, Domain domain)
+	{
+	  Set (node, domain);
+	}
+
+	public void SetArgs (MPlist args)
+	{
+	  int len = args == null ? 0 : args.Count;
+
+	  if (this.args == null)
+	    this.args = new MSymbol[len];
+	  for (int i = 0; i < len; i++, args = args.next)
+	    this.args[i] = args.Symbol;
+	}
+
+	public void SetBody (MPlist body, Domain domain)
+	{
+	  int len = body == null ? 0 : body.Count;
+	  if (this.body == null)
+	    this.body = new MExpression[len];
+	  for (int i = 0; i < len; i++, body = body.next)
+	    {
+	      domain.Translate (body);
+	      this.body[i] = new MExpression (body.key, body.val, domain);
+	    }
+	}
+
+	public void Set (XmlNode node, Domain domain)
+	{
+	  XmlNodeList body = node.ChildNodes;
+	  int idx = 0;
+
+	  if (body[0].Name == "args")
+	    {
+	      XmlNodeList args = body[0].ChildNodes;
+	      if (this.args == null)
+		this.args = new MSymbol[args.Count];
+	      for (int i = 0; i < args.Count; i++)
+		this.args[i] = args[i].InnerText;
+	      idx++;
+	    }
+	  else if (this.args == null)
+	    this.args = new MSymbol[0];
+	  if (this.body == null)
+	    this.body = new MExpression[body.Count - idx];
+	  for (int i = 0; idx < body.Count; i++, idx++)
+	    this.body[i] = new MExpression (body[idx], domain);
+	}
+      }
+
+      public readonly MSymbol Name;
+      public Builtin builtin;
+      public int min_arg, max_arg;
+      internal Lambda lambda;
+      public bool specialp = false;
+
+      internal static Function ignore, varref, block;
+
+      public Function (MSymbol name, Builtin builtin,
+		       int min_arg, int max_arg, bool specialp)
+      {
+	Name = name;
+	this.builtin = builtin;
+	this.min_arg = min_arg;
+	this.max_arg = max_arg;
+	this.specialp = specialp;
+      }
+
+      internal Function (MSymbol name, MPlist args, MPlist body,
+			 Domain domain)
+      {
+	Name = name;
+	lambda = new Lambda (args, body, domain);
+	this.min_arg = this.max_arg = lambda.args.Length;
+      }
+
+      internal Function (MSymbol name, XmlNode node, Domain domain)
+      {
+	Name = name;
+	lambda = new Lambda (node, domain);
+	this.min_arg = this.max_arg = lambda.args.Length;
+      }
+
+      private Function ()
+      {
+	Name = MSymbol.nil;
+      }
+
+      static Function ()
+      {
+	ignore = new Function ();
+	varref = new Function (Mvarref, get_value, 1, 1, true);
+	block = new Function (Mprogn, progn, 0, -1, true);
+      }
+
+      private static object get_value (MExpression[] args, Domain domain)
+      {
+	return domain.GetValue ((MSymbol) args[0].val);
+      }
+
+      public object Call (MExpression[] args, Domain domain)
+      {
+	if (builtin != null)
 	  {
-	    MText mt = new MText ();
-	    foreach (MExpression e in args)
-	      mt += (MText) e.Eval (bindings);
-	    val = mt;
+	    if (! specialp)
+	      foreach (MExpression e in args)
+		e.Eval (domain);
+	    return builtin (args, domain);
 	  }
-	return val;
+	if (lambda == null)
+	  return null;
+	MPlist orig_bindings = domain.bindings;
+	object result = false;
+	try {
+	  int i = 0;
+	  foreach (MSymbol arg in lambda.args)
+	    domain.Bind (arg, args[i++].Eval (domain));
+	  foreach (MExpression e in lambda.body)
+	    result = e.Eval (domain);
+	} finally {
+	  domain.bindings = orig_bindings;
+	}
+	return result;
       }
+    }
+
+    private static Domain basic;
+
+    static MExpression ()
+    {
+      basic = new Domain ();
+
+      basic.Defun ("set", set_value, 2, 2, true);
+      basic.Defun ("=", set_value, 2, 2, true);
+      basic.Defun ("!", not, 1, 1, false);
+      basic.Defun ("+", plus, 2, -1, false);
+      basic.Defun ("*", multi, 2, -1, false);
+      basic.Defun ("-", minus, 1, -1, false);
+      basic.Defun ("/", divide, 2, -1, false);
+      basic.Defun ("%", percent, 2, -1, false);
+      basic.Defun ("|", logior, 2, -1, false);
+      basic.Defun ("&", logand, 2, -1, false);
+      basic.Defun ("+=", pluseq, 2, -1, true);
+      basic.Defun ("*=", multieq, 2, -1, true);
+      basic.Defun ("-=", minuseq, 2, -1, true);
+      basic.Defun ("/=", divideeq, 2, -1, true);
+      basic.Defun ("%=", percenteq, 2, -1, true);
+      basic.Defun ("|=", logioreq, 2, -1, true);
+      basic.Defun ("&=", logandeq, 2, -1, true);
+      basic.Defun ("<<", lshift, 2, 2, false);
+      basic.Defun (">>", rshift, 2, 2, false);
+      basic.Defun ("<<=", lshifteq, 2, 2, true);
+      basic.Defun (">>=", rshifteq, 2, 2, true);
+      basic.Defun ("==", eq, 2, -1, false);
+      basic.Defun ("!=", noteq, 2, 2, false);
+      basic.Defun ("<", less, 2, -1, false);
+      basic.Defun ("<=", lesseq, 2, -1, false);
+      basic.Defun (">", more, 2, -1, false);
+      basic.Defun (">=", moreeq, 2, -1, false);
+      basic.Defun ("progn", progn, 0, -1, true);
+      basic.Defun ("if", ifclause, 2, -1, true);
+      basic.Defun ("when", whenclause, 1, -1, true);
+      basic.Defun ("while", whileclause, 1, -1, true);
+
+      basic.AddTranslator (new Translator (translate_cond));
+    }
+
+    private static object set_value (MExpression[] args, Domain domain)
+    {
+      return domain.SetValue ((MSymbol) args[0].args[0].val,
+			      args[1].Eval (domain));
+    }
 
-      private static object multi (object[] args, MPlist bindings)
+    private static object not (MExpression[] args, Domain domain)
+    {
+      if (args[0].val is int)
+	return (int) args[0].val == 0;
+      if (args[0].val is bool)
+	return ! ((bool) args[0].val);
+      return true;
+    }
+
+    private static object plus (MExpression[] args, Domain domain)
+    {
+      if (args[0].val is int)
+	{
+	  int n = 0;
+	  foreach (MExpression e in args)
+	    n += (int) e.val;
+	  return n;
+	}
+      else if (args[0].val is MText)
+	{
+	  MText mt = new MText ();
+	  foreach (MExpression e in args)
+	    mt += (MText) e.val;
+	  return mt;
+	}
+      throw new Exception ("Not an integer nor MText: " + args[0].val);
+    }
+
+      private static object multi (MExpression[] args, Domain domain)
       {
 	int n = 1;
 	foreach (MExpression e in args)
-	  n *= (int) e.Eval (bindings);
+	  n *= (int) e.val;
 	return n;
       }
 
-      private static object minus (object[] args, MPlist bindings)
+      private static object minus (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
 	if (args.Length == 1)
 	  return - n;
 	for (int i = 1; i < args.Length; i++)
-	  n -= (int) ((MExpression) args[i]).Eval (bindings);
+	  n -= (int) args[i].val;
 	return n;
       }
 
-      private static object divide (object[] args, MPlist bindings)
+      private static object divide (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
 	for (int i = 1; i < args.Length; i++)
-	  n /= (int) ((MExpression) args[i]).Eval (bindings);
+	  n /= (int) args[i].val;
 	return n;
       }
 
-      private static object percent (object[] args, MPlist bindings)
+      private static object percent (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
 	for (int i = 1; i < args.Length; i++)
-	  n %= (int) ((MExpression) args[i]).Eval (bindings);
+	  n %= (int) args[i].val;
 	return n;
       }
 
-      private static object logior (object[] args, MPlist bindings)
+      private static object logior (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
-	for (int i = 1; i < args.Length; i++)
-	  n |= (int) ((MExpression) args[i]).Eval (bindings);
+	int n = 0;
+	foreach (MExpression e in args)
+	  n |= (int) e.val;
 	return n;
       }
 
-      private static object logand (object[] args, MPlist bindings)
+      private static object logand (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
-	for (int i = 1; i < args.Length; i++)
-	  n &= (int) ((MExpression) args[i]).Eval (bindings);
+	int n = 0;
+	foreach (MExpression e in args)
+	  n &= (int) e.val;
 	return n;
       }
 
-      private static object pluseq (object[] args, MPlist bindings)
+      private static object pluseq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	object val = slot.val;
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	object val = domain.GetValue (sym);
 
 	if (val is int)
 	  {
 	    int n = (int) val;
 	    for (int i = 1; i < args.Length; i++)
-	      n += (int) ((MExpression) args[i]).Eval (bindings);
-	    slot.val = n;
+	      n += (int) args[i].Eval (domain);
+	    val = n;
 	  }
 	else if (val is MText)
 	  {
 	    MText mt = (MText) val;
 	    for (int i = 1; i < args.Length; i++)
-	      mt.Cat ((MText) ((MExpression) args[i]).Eval (bindings));
+	      mt.Cat ((MText) args[i].Eval (domain));
+	    val = mt;
 	  }
-	return slot.val;
+	domain.SetValue (sym, val);
+	return val;
       }
 
-      private static object multieq (object[] args, MPlist bindings)
+      private static object multieq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n = (int) slot.val;
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
 	for (int i = 1; i < args.Length; i++)
-	  n *= (int) ((MExpression) args[i]).Eval (bindings);
-	return (slot.val = n);
+	  n *= (int) args[i].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object minuseq (object[] args, MPlist bindings)
+      private static object minuseq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n = (int) slot.val;
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
 	for (int i = 1; i < args.Length; i++)
-	  n -= (int) ((MExpression) args[i]).Eval (bindings);
-	return (slot.val = n);
+	  n -= (int) args[i].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object divideeq (object[] args, MPlist bindings)
+      private static object divideeq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n = (int) slot.val;
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
 	for (int i = 1; i < args.Length; i++)
-	  n /= (int) ((MExpression) args[i]).Eval (bindings);
-	return (slot.val = n);
+	  n /= (int) args[i].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object percenteq (object[] args, MPlist bindings)
+      private static object percenteq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n = (int) slot.val;
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
 	for (int i = 1; i < args.Length; i++)
-	  n %= (int) ((MExpression) args[i]).Eval (bindings);
-	return (slot.val = n);
+	  n %= (int) args[i].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object logioreq (object[] args, MPlist bindings)
+      private static object logioreq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n = (int) slot.val;
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
 	for (int i = 1; i < args.Length; i++)
-	  n |= (int) ((MExpression) args[i]).Eval (bindings);
-	return (slot.val = n);
+	  n |= (int) args[i].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object logandeq (object[] args, MPlist bindings)
+      private static object logandeq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n = (int) slot.val;
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
 	for (int i = 1; i < args.Length; i++)
-	  n &= (int) ((MExpression) args[i]).Eval (bindings);
-	return (slot.val = n);
+	  n &= (int) args[i].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object lshift (object[] args, MPlist bindings)
+      private static object lshift (MExpression[] args, Domain domain)
       {
-	int n1 = (int) ((MExpression) args[0]).Eval (bindings);
-	int n2 = (int) ((MExpression) args[1]).Eval (bindings);
-	return n1 << n2;
+	return (int) args[0].val << (int) args[1].val;
       }
 
-      private static object lshifteq (object[] args, MPlist bindings)
+      private static object lshifteq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n1 = (int) slot.val;
-	int n2 = (int) ((MExpression) args[1]).Eval (bindings);
-	return (slot.val = (n1 << n2));
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
+	n <<= (int) args[1].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object rshift (object[] args, MPlist bindings)
+      private static object rshift (MExpression[] args, Domain domain)
       {
-	int n1 = (int) ((MExpression) args[0]).Eval (bindings);
-	int n2 = (int) ((MExpression) args[1]).Eval (bindings);
-	return n1 >> n2;
+	return (int) args[0].val >> (int) args[1].val;
       }
 
-      private static object rshifteq (object[] args, MPlist bindings)
+      private static object rshifteq (MExpression[] args, Domain domain)
       {
-	MPlist slot = find_binding (args, bindings);
-	int n1 = (int) slot.val;
-	int n2 = (int) ((MExpression) args[1]).Eval (bindings);
-	return (slot.val = (n1 >> n2));
+	MSymbol sym = (MSymbol) args[0].args[0].val;
+	int n = (int) domain.GetValue (sym);
+
+	n >>= (int) args[1].Eval (domain);
+	return domain.SetValue (sym, (object) n);
       }
 
-      private static object eq (object[] args, MPlist bindings)
+      private static object eq (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
+
 	for (int i = 1; i < args.Length; i++)
-	  if (n != (int) ((MExpression) args[i]).Eval (bindings))
-	    return 0;
-	return 1;
+	  if (n != (int) args[i].val)
+	    return false;
+	return true;
       }
 
-      private static object noteq (object[] args, MPlist bindings)
+      private static object noteq (MExpression[] args, Domain domain)
       {
-	int n1 = (int) ((MExpression) args[0]).Eval (bindings);
-	int n2 = (int) ((MExpression) args[1]).Eval (bindings);
-	return (n1 != n2);
+	return ((int) args[0].val != (int) args[1].val);
       }
 
-      private static object less (object[] args, MPlist bindings)
+      private static object less (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
+
 	for (int i = 1; i < args.Length; i++)
 	  {
-	    int n1 = (int) ((MExpression) args[i]).Eval (bindings);
+	    int n1 = (int) args[i].val;
 	    if (n >= n1)
-	      return 0;
+	      return false;
 	    n = n1;
 	  }
-	return 1;
+	return true;
       }
 
-      private static object lesseq (object[] args, MPlist bindings)
+      private static object lesseq (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
 	for (int i = 1; i < args.Length; i++)
 	  {
-	    int n1 = (int) ((MExpression) args[i]).Eval (bindings);
+	    int n1 = (int) args[i].val;
 	    if (n > n1)
-	      return 0;
+	      return false;
 	    n = n1;
 	  }
-	return 1;
+	return true;
       }
 
-      private static object more (object[] args, MPlist bindings)
+      private static object more (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
 	for (int i = 1; i < args.Length; i++)
 	  {
-	    int n1 = (int) ((MExpression) args[i]).Eval (bindings);
+	    int n1 = (int) args[i].val;
 	    if (n <= n1)
-	      return 0;
+	      return false;
 	    n = n1;
 	  }
-	return 1;
+	return true;
       }
 
-      private static object moreeq (object[] args, MPlist bindings)
+      private static object moreeq (MExpression[] args, Domain domain)
       {
-	int n = (int) ((MExpression) args[0]).Eval (bindings);
+	int n = (int) args[0].val;
 	for (int i = 1; i < args.Length; i++)
 	  {
-	    int n1 = (int) ((MExpression) args[i]).Eval (bindings);
+	    int n1 = (int) args[i].val;
 	    if (n < n1)
-	      return 0;
+	      return false;
 	    n = n1;
 	  }
-	return 1;
+	return true;
       }
 
-      private static object progn (object[] args, MPlist bindings)
+      private static object progn (MExpression[] args, Domain domain)
       {
-	object result = null;
+	object result = false;
 
 	foreach (MExpression e in args)
-	  result = e.Eval (bindings);
+	  result = e.Eval (domain);
 	return result;
       }
 
-      private static void block_pp (Function func,
-				    string indent, object[] args)
-      {
-	bool first = true;
-
-	Console.Write ("(");
-	indent += " ";
-	foreach (MExpression e in args)
-	  {
-	    if (first)
-	      first = false;
-	    else
-	      Console.Write ("\n" + indent);
-	    e.pp (indent);
-	  }
-	Console.Write (")");
-      }
-
-      private static bool check_condition (MExpression e, MPlist bindings)
-      {
-	object result = e.Eval (bindings);
-	return (! (result is int) || (int) result != 0);
-      }
-
-      private static object cond (object[] args, MPlist bindings)
-      {
-	foreach (MExpression[] elist in args)
-	  if (check_condition (elist[0], bindings))
-	    {
-	      object result = 0;
-	      for (int i = 1; i < elist.Length; i++)
-		result = elist[i].Eval (bindings);
-	      return result;
-	    }
-	return 0;
-      }
-
-      private static void cond_pp (Function func,
-				   string indent, object[] args)
+      private static bool check_condition (MExpression condition, Domain domain)
       {
-	Console.Write ("(cond");
-	indent += "  ";
-	foreach (MExpression[] expr_list in args)
-	  {
-	    Console.Write ("\n" + indent + "(");
-	    bool first = true;
-	    foreach (MExpression e in expr_list)
-	      {
-		if (first)
-		  first = false;
-		else
-		  Console.Write (" ");
-		e.pp (indent);
-	      }
-	    Console.Write (")");
-	  }
-	Console.Write (")");
+	object result = condition.Eval (domain);
+	return (result is bool ? (bool) result
+		: result is int ? ((int) result) != 0
+		: true);
       }
 
-      private static object ifclause (object[] args, MPlist bindings)
+      private static object ifclause (MExpression[] args, Domain domain)
       {
-	object result = 0;
+	object result = false;
 
-	if (check_condition ((MExpression) args[0], bindings))
-	  result = ((MExpression) args[1]).Eval (bindings);
+	if (check_condition (args[0], domain))
+	  result = args[1].Eval (domain);
 	else
 	  for (int i = 2; i < args.Length; i++)
-	    result = ((MExpression) args[i]).Eval (bindings);
+	    result = args[i].Eval (domain);
 	return result;
       }
 
-      private static void if_pp (Function func,
-				 string indent, object[] args)
+      private static object whenclause (MExpression[] args, Domain domain)
       {
-	Console.Write ("(if ");
-	((MExpression) args[0]).pp (indent + "    ");
-	Console.Write ("\n" + indent + "    ");
-	((MExpression) args[1]).pp (indent + "    ");
-	indent += "  ";
-	for (int i = 2; i < args.Length; i++)
-	  {
-	    Console.Write ("\n" + indent);
-	    ((MExpression) args[i]).pp (indent);
-	  }
-	Console.Write (")");
-      }
-
-      private static object whileclause (object[] args, MPlist bindings)
-      {
-	object result = 0;
+	object result = false;
 
-	while (check_condition ((MExpression) args[0], bindings))
+	if (check_condition (args[0], domain))
 	  for (int i = 1; i < args.Length; i++)
-	    result = ((MExpression) args[i]).Eval (bindings);
+	    result = args[i].Eval (domain);
 	return result;
       }
 
-      private static void while_pp (Function func,
-				    string indent, object[] args)
-      {
-	Console.Write ("(while ");
-	((MExpression) args[0]).pp (indent + "       ");
-	bool first = true;
-	indent += "  ";
-	for (int i = 1; i < args.Length; i++)
-	  {
-	    if (first)
-	      {
-		Console.Write ("\n" + indent);
-		first = false;
-	      }
-	    else
-	      Console.Write (" ");
-	    ((MExpression) args[i]).pp (indent);
-	  }
-	Console.Write (")");
-      }
-
-      private static object define_function (object[] args, MPlist bindings)
-      {
-	FunctionTable table = (FunctionTable) args[0];
-	MSymbol sym = (MSymbol) args[1];
-	MPlist arg_symbols = (MPlist) args[2];
-	int nargs = arg_symbols.Count;
-	object[] data = new object[args.Length - 2];
-
-	data[0] = args[2];
-	for (int i = 3; i < args.Length; i++)
-	  data[i - 2] = args[i];
-
-	Function func = new Function (sym, null, nargs, nargs,
-				      typeof (MExpression));
-	table.table[sym] = func;
-	func.data = data;
-	return null;
-      }
-
-      private static void defun_pp (Function func,
-				    string indent, object[] args)
+      private static object whileclause (MExpression[] args, Domain domain)
       {
-	Console.Write ("(defun " + args[1] + " " + args[2]);
-	bool first = true;
-	indent += "  ";
-	for (int i = 3; i < args.Length; i++)
-	  {
-	    if (first)
-	      {
-		Console.Write ("\n" + indent);
-		first = false;
-	      }
-	    else
-	      Console.Write (" ");
-	    ((MExpression) args[i]).pp (indent);
-	  }
-	Console.Write (")");
+	while (check_condition (args[0], domain))
+	  for (int i = 1; i < args.Length; i++)
+	    args[i].Eval (domain);
+	return false;
       }
-    }
-
-    public class FunctionTable
-    {
-      internal Dictionary<MSymbol, Function> table
-	= new Dictionary<MSymbol, Function> ();
-    }
-
-    private static FunctionTable basic_table = new FunctionTable ();
-
-    public static void Defun (FunctionTable table, string name,
-			      Evaluator evaluator, int min_arg, int max_arg,
-			      params Type[] arg_types)
-    {
-      Function func = Defun (name, evaluator, min_arg, max_arg, arg_types);
-      table.table[func.name] = func;
-    }
-
-    private static Function Defun (string name, Evaluator evaluator,
-				   int min_arg, int max_arg,
-				   params Type[] arg_types)
-    {
-      MSymbol sym = MSymbol.Of (name);
-      Function func = new Function (sym, evaluator, min_arg, max_arg,
-				      arg_types);
-      basic_table.table[sym] = func;
-      return func;
-    }
-
-    private static Function Defun (string name, Evaluator evaluator,
-				    int min_arg, int max_arg)
-    {
-      return Defun (name, evaluator, min_arg, max_arg, typeof (MExpression));
-    }
-
-    private static Function Find (MSymbol name, FunctionTable table)
-    {
-      if (name == MSymbol.integer
-	  || name == MSymbol.mtext)
-	return Function.literal;
-
-      Function func;
-      if ((table == null
-	   || ! table.table.TryGetValue (name, out func))
-	  && ! basic_table.table.TryGetValue (name, out func))
-	return null;
-      return func;
-    }
-
-    private void invalid_expression (object o)
-    {
-      throw new Exception ("Invalid expresssion: " + o);
-    }
-
-    private void invalid_argument (object o)
-    {
-      throw new Exception (String.Format ("Invalid argument to {0}: {1}",
-					  function.name, o));
-    }
-
-    private Function function;
-    private object[] args;
-
-    public MExpression (MSymbol function_name, object[] args,
-			FunctionTable function_table)
-    {
-      function = Find (function_name, function_table);
-      int nargs = args.Length;
-      if (nargs < function.min_arg
-	  || (function.max_arg >= 0 && nargs > function.max_arg))
-	throw new Exception (String.Format ("Invalid number of arguments to {0}: {1}", function.name, nargs));
-      this.args = (object[]) args.Clone ();
-    }
 
-    private MExpression[] expression_list (MPlist plist, FunctionTable table)
+    // (cond (COND1 ...) (COND2 ...) ...)
+    //   => (cond (when COND1 ...) (when COND2 ...) ...)
+    private static void translate_cond (MPlist plist, Domain domain)
     {
-      int len = plist.Count;
-      MExpression[] expr_list = new MExpression[len];
-
-      for (int i = 0; i < len; i++, plist = plist.next)
+      if (plist.IsPlist)
 	{
-	  if (plist.IsSymbol)
-	    expr_list[i] = new MExpression (plist.Symbol);
-	  else if (plist.IsMText || plist.IsInteger)
-	    expr_list[i] = new MExpression (plist.val);
-	  else if (plist.IsPlist)
+	  plist = plist.Plist;
+	  if (plist.IsSymbol && plist.Symbol == Mcond)
 	    {
-	      MPlist p = plist.Plist;
-	      if (p.IsSymbol)
-		expr_list[i] = new MExpression (p.Symbol, p.next, table);
-	      else
-		expr_list[i] = new MExpression (p, table);
+	      plist.val = Mprogn;
+	      for (plist = plist.next; ! plist.IsEmpty; plist = plist.next)
+		{
+		  if (! plist.IsPlist)
+		    throw new Exception ("Invalid cond form: " + plist);
+		  plist.Plist.Push (MSymbol.symbol, Mwhen);
+		}		
 	    }
-	  else
-	    invalid_expression (plist.val);
 	}
-      return expr_list;
     }
 
-    // EXPR = SYMBOL | MTEXT | INTEGER | FUNCALL | EXPRLIST
-    // FUNCALL = '(' SYMBOL EXPR* ')'
-    // EXPRLIST = '(' EXPR* ')'
+    private Function function;
+    private MExpression[] args;
+    private object val;
 
-    // EXPRLIST: PLIST = EXPR ...
-    public MExpression (MPlist plist, FunctionTable table)
+    public MExpression[] Args { get { return args; } }
+    public object Val { get { return val; } }
+
+    private MExpression (object val)
     {
-      function = Function.block;
-      args = expression_list (plist, table);
+      this.val = val;
     }
 
-    // FUNCALL: NAME = FUNCTION-NAME, ARG-LIST = EXPR ...
-    private MExpression (MSymbol name, MPlist arg_list, FunctionTable table)
+    // EXPR = SYMBOL | MTEXT | INTEGER | FUNCALL | PROGN
+    // FUNCALL = '(' SYMBOL EXPR* ')'
+    // PROGN = '(' EXPR * ')'
+    private MExpression (MSymbol key, object val, Domain domain)
     {
-      function = Find (name, table);
-      if (function == null)
-	throw new Exception ("Unknown function: " + name);
-
-      int nargs = arg_list.Count;
-      if (nargs < function.min_arg
-	  || (function.max_arg >= 0 && nargs > function.max_arg))
-	throw new Exception (String.Format
-			     ("Invalid number of arguments to {0}: {1}",
-			      function.name, nargs));
-
-      int i = 0;
-      Type arg_type = typeof (MExpression);
-      if (function.arg_types.Length > 0)
+      if (key == MSymbol.symbol)
 	{
-	  arg_type = function.arg_types[0];
-	  if (arg_type == typeof (FunctionTable))
-	    {
-	      nargs++;
-	      args = new object[nargs];
-	      args[i++] = table;
-	    }
-	  else
-	    args = new object[nargs];
+	  function = Function.varref;
+	  args = new MExpression[1];
+	  args[0] = new MExpression (val);
 	}
-      else
-	args = new object[nargs];
-
-      foreach (MPlist p in arg_list)
+      else if (key == MSymbol.integer
+	       || key == MSymbol.mtext)
+	{
+	  this.val = val;
+	}
+      else if (key == MSymbol.plist)
 	{
-	  if (i < function.arg_types.Length)
-	    arg_type = function.arg_types[i];
-	  if (arg_type == typeof (MExpression))
+	  MPlist p = (MPlist) val;
+
+	  if (p.IsSymbol)
 	    {
-	      if (p.IsSymbol)
-		args[i++] = new MExpression (p.Symbol);
-	      else if (p.IsMText || p.IsInteger)
-		args[i++] = new MExpression (p.val);
-	      else if (p.IsPlist)
+	      MSymbol sym = p.Symbol;
+
+	      if (sym == Mdefun)
 		{
-		  MPlist p0 = p.Plist;
-		  if (p0.IsSymbol)
-		    args[i++] = new MExpression (p0.Symbol, p0.next, table);
-		  else
-		    args[i++] = new MExpression (p0, table);
+		  p = p.next;
+		  if (! p.IsSymbol)
+		    throw new Exception ("Invalid function argument: "
+					 + p.val);
+		  sym = p.Symbol;
+		  p = p.next;
+		  if (! p.IsPlist)
+		    throw new Exception ("Invalid function argument: "
+					 + p.val);
+		  domain.Defun (sym, p.Plist, p.next);
+		  // This Mexpression is just a dummy.
 		}
 	      else
-		invalid_expression (p.val);
-	    }
-	  else if (arg_type == typeof (MExpression[]))
-	    {
-	      if (! p.IsPlist)
-		invalid_argument (p.val);
-	      args[i++] = expression_list (p.Plist, table);
+		{
+		  function = domain.GetFunc (sym);
+		  p = p.next;
+		  int nargs = p.Count;
+		  if (nargs < function.min_arg
+		      || (function.max_arg >= 0 && nargs > function.max_arg))
+		    throw new Exception ("Invalid number of arguments to: "
+					 + sym + " " + nargs);
+		  args = new MExpression[nargs];
+		  for (int i = 0; i < nargs; i++, p = p.next)
+		    {
+		      domain.Translate (p);
+		      args[i] = new MExpression (p.key, p.val, domain);
+		    }
+		}
 	    }
-	  else if (arg_type == typeof (MSymbol))
+	  else
 	    {
-	      if (! p.IsSymbol)
-		invalid_argument (p.val);
-	      args[i++] = p.Symbol;
+	      args = new MExpression[1];
+	      args[0] = new MExpression (p, domain);
 	    }
-	  else
-	    args[i++] = p.val;
 	}
-      if (function == Function.defun)
-	function.Call (args, null);
+      else
+	throw new Exception ("Invalid expression: " + key + ":" + val);
     }
 
-    public MExpression (MSymbol sym)
+    public MExpression (MPlist plist, Domain domain)
     {
-      function = Function.varref;
-      args = new object[1];
-      args[0] = sym;
+      function = Function.block;
+      args = new MExpression[plist.Count];
+      for (int i = 0; ! plist.IsEmpty; i++, plist = plist.next)
+	{
+	  domain.Translate (plist);
+	  args[i] = new MExpression (plist.key, plist.val, domain);
+	}
     }
 
-    public MExpression (object obj)
+    public MExpression (XmlNode node, Domain domain)
     {
-      function = Function.literal;
-      args = new object[1];
-      args[0] = obj;
+      MSymbol sym = node.Name;
+
+      function = domain.GetFunc (sym);
+
+      XmlAttributeCollection attrs = node.Attributes;
+
+      int nargs = attrs.Count + node.ChildNodes.Count;
+      if (nargs < function.min_arg
+	  || (function.max_arg >= 0 && nargs > function.max_arg))
+	throw new Exception ("Invalid number of arguments: " + node.InnerXml);
+      args = new MExpression[nargs];
+      int i;
+      for (i = 0; i < attrs.Count; i++)
+	{
+	  string str = sttrs[i].Value;
+
+	}
     }
 
-    public object Eval (MPlist bindings)
+    public object Eval (Domain domain)
     {
-      return function.Call (args, bindings);
+      if (function == null)
+	{
+	  if (val is MSymbol)
+	    val = domain.GetValue ((MSymbol) val);
+	}
+      else
+	val = function.Call (args, domain);
+      return val;
     }
 
-    private void pp (string indent)
+    public override string ToString ()
     {
-      if (function == Function.varref
-	  || function == Function.literal)
+      string str;
+
+      if (function != null)
 	{
-	  if (args[0] is MText)
-	    Console.Write ("\"{0}\"", args[0]);
+	  str = "(" + function.Name.Name;
+	  if (args != null)
+	    foreach (MExpression e in args)
+	      str += " " + e.ToString ();
+	  str += ")";
+	}
+      else if (val != null)
+	{
+	  if (val is MText)
+	    str = "\"" + (string) ((MText) val) + "\"";
 	  else
-	    Console.Write (args[0]);
+	    str = val.ToString ();
 	}
       else
-	function.pp (function, indent, args);
+	str = "()";
+      return str;
     }
-
-    public void PrettyPrint () { pp (""); }
   }
 }