diff --git a/src/core/org/luaj/lib/BaseLib.java b/src/core/org/luaj/lib/BaseLib.java
index ba79ebfa..e45aa7ec 100644
--- a/src/core/org/luaj/lib/BaseLib.java
+++ b/src/core/org/luaj/lib/BaseLib.java
@@ -109,7 +109,7 @@ public class BaseLib extends LFunction {
 		vm.pushnil();
 		vm.pushstring( message );
 	}
-	
+
 	private void checkargexists(LuaState vm, int index, int type) {
 		if ( vm.gettop() < index )
 			vm.error("bad argument #"+(index-1)+" to '?' ("+
@@ -120,8 +120,13 @@ public class BaseLib extends LFunction {
 
 	private void checkargtype(LuaState vm, int index, int type) {		
 		checkargexists( vm, index, type );
-		if ( vm.type(index) != type )
-			vm.error("bad argument #"+(index-1)+" to '?' ("+Lua.TYPE_NAMES[type]+" expected, got "+vm.typename(index)+")");		
+		int t = vm.type(index);
+		if ( t != type ) {
+			if ( type == Lua.LUA_TNUMBER && t == Lua.LUA_TSTRING && vm.isnumber(index) )
+				return;
+			vm.error("bad argument #"+(index-1)+" to '?' ("+
+					Lua.TYPE_NAMES[type]+" expected, got "+vm.typename(index)+")");
+		}
 	}
 
 	public boolean luaStackCall(LuaState vm) {
@@ -139,13 +144,15 @@ public class BaseLib extends LFunction {
 		}
 		case PAIRS:
 		case IPAIRS: {
-			LValue v = vm.topointer(2);
+			checkargtype(vm,2,Lua.LUA_TTABLE);
+			LTable v = vm.totable(2);
 			LValue r = v.luaPairs(id==PAIRS);
 			vm.resettop();
 			vm.pushlvalue( r );
 			break;
 		}
 		case GETMETATABLE: {
+			checkargexists(vm,2,Lua.LUA_TVALUE);
 			if ( 0 == vm.getmetatable(2) ) {
 				vm.resettop();
 				vm.pushnil();
@@ -156,8 +163,7 @@ public class BaseLib extends LFunction {
 			break;
 		}
 		case SETMETATABLE: {
-			if ( ! vm.istable(2) )
-				vm.error("bad argument #1 to '?' (table expected, got "+vm.typename(2)+")");
+			checkargtype(vm,2,Lua.LUA_TTABLE);
 			vm.setmetatable(2);
 			vm.remove(1);
 			break;
@@ -200,13 +206,14 @@ public class BaseLib extends LFunction {
 			break;
 			
 		case TONUMBER: {
+			checkargexists(vm,2,Lua.LUA_TVALUE);
 			switch ( vm.type(2) ) {
 			case Lua.LUA_TNUMBER:
 				break;
 			case Lua.LUA_TSTRING:
 				LString s = vm.tolstring(2);
 				int base = 10;
-				if ( vm.gettop() >= 3 ) {
+				if ( vm.isnumber(3) ) {
 					base = vm.tointeger(3);
 					if ( base < 2 || base > 36 )
 						vm.error("bad argument #2 to '?' (base out of range)");
@@ -273,9 +280,8 @@ public class BaseLib extends LFunction {
 			break;
 		}
 		case SELECT: {
+			checkargexists(vm,2,Lua.LUA_TNUMBER);
 			int n = vm.gettop();
-			if ( n < 2 )  
-				vm.error( "bad argument #1 to '?' (number expected, got no value)" );
 			if ( vm.isnumber(2) ) {
 				int index = vm.tointeger(2);
 				if ( index < 0 )
@@ -320,26 +326,27 @@ public class BaseLib extends LFunction {
 			load(vm, vm.topointer(2), vm.tostring(3));
 			break;
 		case TOSTRING: {
-			if ( vm.gettop() < 2 )  
-				vm.error( "bad argument #1 to '?' (value expected)" );
+			checkargexists(vm,2,Lua.LUA_TVALUE);
 			LValue v = vm.topointer(2);
 			vm.resettop();
 			vm.pushlvalue( v.luaAsString() );			
 			break;
 		}
 		case UNPACK: {
-			int n = vm.gettop();
-			if ( n < 2 )  
-				vm.error( "bad argument #1 to '?' (table expected, got no value)" );
-			if ( ! vm.istable(2) )
-				vm.error( "bad argument #1 to '?' (table expected, got "+vm.typename(2)+")" );
+			checkargtype(vm,2,Lua.LUA_TTABLE);
 			LTable list = vm.totable(2);
-			int i = vm.tointeger(3);
-			int j = vm.tointeger(4);
-			if ( n <= 2 )
-				i = 1;
-			if ( n <= 3 )
+			int n = vm.gettop();
+			int i=1,j;
+			if ( n >= 3 ) {
+				checkargtype(vm,3,Lua.LUA_TNUMBER);
+				i = vm.tointeger(3);
+			}
+			if ( n >= 4 ) {
+				checkargtype(vm,4,Lua.LUA_TNUMBER);
+				j = vm.tointeger(4);
+			} else {
 				j = list.luaLength();
+			}
 			vm.resettop();
 			vm.checkstack(j+1-i);
 			for ( int k=i; k<=j; k++ )
@@ -347,7 +354,11 @@ public class BaseLib extends LFunction {
 			break;
 		}
 		case NEXT: {
-			setResult( vm, next(vm, vm.topointer(2), vm.tointeger(3)) );
+			checkargtype(vm,2,Lua.LUA_TTABLE);
+			LTable t = vm.totable(2);
+			LValue v = vm.topointer(3);
+			vm.resettop();
+			t.next(vm,v);
 			break;
 		}
 		default:
@@ -474,11 +485,4 @@ public class BaseLib extends LFunction {
 			closeSafely( baos );
 		}
 	}
-
-	private LValue next(LuaState vm, LValue table, int index) {
-		throw new LuaErrorException("next() not supported yet");
-	}
-
-	
-
 }
diff --git a/src/core/org/luaj/vm/LNumber.java b/src/core/org/luaj/vm/LNumber.java
index 01633cd1..ed3fe15f 100644
--- a/src/core/org/luaj/vm/LNumber.java
+++ b/src/core/org/luaj/vm/LNumber.java
@@ -78,4 +78,9 @@ public class LNumber extends LValue {
 		return new Short(toJavaShort());
 	}
 	
+	/** Convert to a number if possible, or nil otherwise */
+	public LValue luaToNumber() {
+		return this;
+	}
+
 }
diff --git a/src/core/org/luaj/vm/LTable.java b/src/core/org/luaj/vm/LTable.java
index a775634b..a24c4061 100644
--- a/src/core/org/luaj/vm/LTable.java
+++ b/src/core/org/luaj/vm/LTable.java
@@ -635,4 +635,59 @@ public class LTable extends LValue {
 		m_vector[j] = tmp;
 	}
 
+	/**
+	 * Leave nil on top, or index,value pair
+	 * @param vm
+	 * @param index
+	 */
+	public void next(LuaState vm, LValue index) {
+		
+		// look through vector first
+		int start = index.toJavaInt();
+		if ( start > 0 && start <= m_vector.length ) {
+			for ( int i=start; i<m_vector.length; i++ ) {
+				if ( m_vector[i] != LNil.NIL ) {
+					vm.pushinteger(i+1);
+					vm.pushlvalue(m_vector[i]);
+					return;
+				}
+			}
+		}		
+
+		// look up key first
+		if ( index != LNil.NIL ) {
+			if ( m_hashEntries != 0 && (start <= 0 || start > m_vector.length) ) {
+				for ( int i=0; i<m_hashKeys.length; i++ ) { 
+					if ( index.luaBinCmpUnknown( Lua.OP_EQ, m_hashKeys[i] ) ) {
+						start = m_vector.length+i+1;
+						break;
+					}
+				}
+			}
+		}
+		
+		// start looking
+		if ( start < m_vector.length ) {
+			if ( m_arrayEntries != 0 ) {
+				for ( int i=start; i<m_vector.length; i++ ) {
+					if ( m_vector[i] != LNil.NIL ) {
+						vm.pushinteger(i+1);
+						vm.pushlvalue(m_vector[i]);
+						return;
+					}
+				}
+				start = m_vector.length;
+			}
+			if ( m_hashEntries != 0 ) {
+				for ( int i=start-m_vector.length; i<m_hashKeys.length; i++ ) { 
+					if ( index.luaBinCmpUnknown( Lua.OP_EQ, m_hashKeys[i] ) ) {
+						vm.pushlvalue(m_hashKeys[i]);
+						vm.pushlvalue(m_hashValues[i]);
+						return;
+					}
+				}
+			}
+		}
+		vm.pushnil();
+	}
 }
diff --git a/src/core/org/luaj/vm/LValue.java b/src/core/org/luaj/vm/LValue.java
index 1922dca0..a13188ee 100644
--- a/src/core/org/luaj/vm/LValue.java
+++ b/src/core/org/luaj/vm/LValue.java
@@ -302,4 +302,9 @@ public class LValue {
 		return 0;
 	}
 
+	/** Convert to a number if possible, or nil otherwise */
+	public LValue luaToNumber() {
+		return LNil.NIL;
+	}
+
 }
diff --git a/src/core/org/luaj/vm/LuaState.java b/src/core/org/luaj/vm/LuaState.java
index 80be51ac..d9eec20a 100644
--- a/src/core/org/luaj/vm/LuaState.java
+++ b/src/core/org/luaj/vm/LuaState.java
@@ -169,6 +169,8 @@ public class LuaState extends Lua {
         }
         calls[newcc] = new CallInfo(c, base, top, resultbase, nresults);
         cc = newcc;
+        
+        stackClear( top, base + c.p.maxstacksize );        
     }
     
 	/**
@@ -461,6 +463,12 @@ public class LuaState extends Lua {
         top = newTop;
     }
     
+	private final void stackClear(int startIndex, int endIndex) {
+		for (; startIndex < endIndex; startIndex++) {
+			stack[startIndex] = LNil.NIL;
+		}
+	}    
+
     /** execute instructions up to a yield, return, or call */
     public void exec() {
         if ( cc < 0 )
@@ -1460,9 +1468,20 @@ public class LuaState extends Lua {
 	 * string convertible to a number, and 0&nbsp;otherwise.
 	 */
 	public boolean isnumber(int index) {
-		return type(index) == Lua.LUA_TNUMBER;
+		return tolnumber(index) != LNil.NIL;
 	}
 
+	/** 
+	 * Convert a value to an LNumber<span class="apii">[-0, +0, <em>-</em>]</span>
+	 * 
+	 * <p>
+	 * Returns an LNumber if the value at the given acceptable index is a number or a
+	 * string convertible to a number, and LNil.NIL&nbsp;otherwise.
+	 */
+	public LValue tolnumber(int index) {
+		return topointer(index).luaToNumber();
+	}
+	
 	/**
 	 * Test if a value is a string <span class="apii">[-0, +0, <em>m</em>]</span>
 	 *