use an empty string cache

Author: yuin

iolib.go

@@ -372,7 +372,7 @@ func fileReadAux(L *LState, file *lFile, idx int) int {
 					var buf []byte
 					buf, err = ioutil.ReadAll(file.reader)
 					if err == io.EOF {
-						L.Push(LString(""))
+						L.Push(emptyLString)
 						goto normalreturn
 					}
 					if err != nil {

loadlib.go

@@ -63,7 +63,7 @@ func OpenPackage(L *LState) int {
 	L.SetField(L.Get(RegistryIndex), "_LOADED", loaded)
 
 	L.SetField(packagemod, "path", LString(loGetPath(LuaPath, LuaPathDefault)))
-	L.SetField(packagemod, "cpath", LString(""))
+	L.SetField(packagemod, "cpath", emptyLString)
 
 	L.Push(packagemod)
 	return 1

stringlib.go

@@ -7,6 +7,8 @@ import (
 	"github.com/yuin/gopher-lua/pm"
 )
 
+const emptyLString LString = LString("")
+
 func OpenString(L *LState) int {
 	var mod *LTable
 	//_, ok := L.G.builtinMts[int(LTString)]
@@ -391,7 +393,7 @@ func strRep(L *LState) int {
 	str := L.CheckString(1)
 	n := L.CheckInt(2)
 	if n < 0 {
-		L.Push(LString(""))
+		L.Push(emptyLString)
 	} else {
 		L.Push(LString(strings.Repeat(str, n)))
 	}
@@ -415,7 +417,7 @@ func strSub(L *LState) int {
 	end := luaIndex2StringIndex(str, L.OptInt(3, -1), false)
 	l := len(str)
 	if start >= l || end < start {
-		L.Push(LString(""))
+		L.Push(emptyLString)
 	} else {
 		L.Push(LString(str[start:end]))
 	}

tablelib.go

@@ -56,14 +56,14 @@ func tableConcat(L *LState) int {
 	j := L.OptInt(4, tbl.Len())
 	if L.GetTop() == 3 {
 		if i > tbl.Len() || i < 1 {
-			L.Push(LString(""))
+			L.Push(emptyLString)
 			return 1
 		}
 	}
 	i = intMax(intMin(i, tbl.Len()), 1)
 	j = intMin(intMin(j, tbl.Len()), tbl.Len())
 	if i > j {
-		L.Push(LString(""))
+		L.Push(emptyLString)
 		return 1
 	}
 	//TODO should flushing?