Add __unm and __len metatags.

src/core/org/luaj/vm2/LuaClosure.java

@@ -26,8 +26,6 @@ import org.luaj.vm2.lib.DebugLib;
 public class LuaClosure extends LuaFunction {
 	private static final UpValue[] NOUPVALUES = new UpValue[0];
 	
-	public LuaValue s_metatable;
-
 	public final Prototype p;
 	public final UpValue[] upValues;
 	

src/core/org/luaj/vm2/LuaString.java

@@ -109,7 +109,7 @@ public class LuaString extends LuaValue {
 	}
 
 	// unary operators
-	public LuaValue neg() { return valueOf(-checkarith()); }
+	public LuaValue neg() { double d = scannumber(10); return Double.isNaN(d)? super.neg(): valueOf(-d); }
 
 	// basic binary arithmetic
 	public LuaValue   add( LuaValue rhs )      { double d = scannumber(10); return Double.isNaN(d)? arithmt(ADD,rhs): rhs.add(d); }

src/core/org/luaj/vm2/LuaValue.java

@@ -72,6 +72,8 @@ public class LuaValue extends Varargs {
 	public static final LuaString MUL         = valueOf("__mul");
 	public static final LuaString POW         = valueOf("__pow");
 	public static final LuaString MOD         = valueOf("__mod");
+	public static final LuaString UNM         = valueOf("__unm");
+	public static final LuaString LEN         = valueOf("__len");
 	public static final LuaString EMPTYSTRING = valueOf("");
 	
 	private static int MAXSTACK = 250;
@@ -247,9 +249,9 @@ public class LuaValue extends Varargs {
 	
 	// unary operators
 	public LuaValue not()  { return FALSE;  }
-	public LuaValue neg()  { return aritherror("neg");  }
-	public LuaValue len()  { return lenerror(); }
-	public int length() { error("attempt to get length of "+typename()); return 0; }
+	public LuaValue neg()  { return checkmetatag(UNM, "attempt to perform arithmetic on ").call(this);  }
+	public LuaValue len()  { return checkmetatag(LEN, "attempt to get length of ").call(this);  }
+	public int length()    { return len().toint(); }
 	public LuaValue getn() { return typerror("getn"); }
 	
 	// object equality, used for key comparison

test/lua/metatags.lua

@@ -3,7 +3,7 @@ local anumber   = 111
 local aboolean  = false
 local afunction = function() end
 local athread   = coroutine.create( afunction )
-local values = { athread, aboolean, afunction, athread }
+local values = { anumber, aboolean, afunction, athread }
 for i=1,#values do
 	print( debug.getmetatable( values[i] ) )
 end
@@ -13,7 +13,14 @@ tostring = function(o)
 	return (t=='thread' or t=='function') and t or ts(o)
 end
 
-local buildbin = function(name)
+local buildunop = function(name)
+	return function(a)
+		print( 'mt.__'..name..'()', type(a), a )
+		return '__'..name..'-result'
+	end
+end
+
+local buildbinop = function(name)
 	return function(a,b)
 		print( 'mt.__'..name..'()', type(a), type(b), a, b )
 		return '__'..name..'-result'
@@ -25,12 +32,14 @@ local mt = {
 		print( 'mt.__call()', type(a), type(b), type(c), b, c )
 		return '__call-result'
 	end,
-	__add=buildbin('add'),
-	__sub=buildbin('sub'),
-	__mul=buildbin('mul'),
-	__div=buildbin('div'),
-	__pow=buildbin('pow'),
-	__mod=buildbin('mod'),
+	__add=buildbinop('add'),
+	__sub=buildbinop('sub'),
+	__mul=buildbinop('mul'),
+	__div=buildbinop('div'),
+	__pow=buildbinop('pow'),
+	__mod=buildbinop('mod'),
+	__unm=buildunop('unm'),
+	__len=buildunop('neg'),
 }
 
 -- pcall a function and check for a pattern in the error string
@@ -80,10 +89,22 @@ for i=1,#groups do
 	print( debug.setmetatable( a, nil ) )
 end
 
-
-
-print( '---- final metatables' )
+print( '---- __len' )
+values = { aboolean, afunction, athread }
 for i=1,#values do
-	print( debug.getmetatable( values[i] ) )
+	print( type(values[i]), 'before', ecall( 'attempt to get length of ', function() return #values[i] end ) )
+	print( debug.setmetatable( values[i], mt ) )
+	print( type(values[i]), 'after', pcall( function() return #values[i] end ) )
+	print( debug.setmetatable( values[i], nil ) )
 end
 
+print( '---- __neg' )
+values = { aboolean, afunction, athread, "abcd" }
+for i=1,#values do
+	print( type(values[i]), 'before', ecall( 'attempt to get length of ', function() return #values[i] end ) )
+	print( debug.setmetatable( values[i], mt ) )
+	print( type(values[i]), 'after', pcall( function() return #values[i] end ) )
+	print( debug.setmetatable( values[i], nil ) )
+end
+
+