adding missing file

src60/extensions/formatter.l

@@ -0,0 +1,74 @@
+import system'text;
+
+singleton helper
+{
+   readIndex(string s, ref int i, ref int retVal)
+   {
+      char ch := $0;
+      int  n := 0;
+      int  v := 0;
+
+      ch := s[i];
+
+      while (ch != $125)
+      {
+         n := intConvertor.convert(ch);
+         if(n >= 30h && n <= 39h)
+         {              
+            n := n - 30h;
+
+            v := v * 10;
+            v := v + n
+         }
+         else
+         { 
+            InvalidArgumentException.raise()
+         };
+
+         i := i + 1;  
+         ch := s[i];
+      };
+
+      retVal := v
+   }
+}
+
+public extension stringFormatterOp : String
+{
+   interpolate(params object[] args)
+   {
+      auto buffer := new TextBuilder();
+
+      int  len := self.Length;
+      int  i := 0;
+      char ch := $0;
+      int  chlen := 0;
+      int  index := 0;
+
+      while (i < len)
+      {
+         ch := self[i];
+
+         if (ch == $123)
+         {
+            i := i + 1;
+
+            helper.readIndex(self, ref i, ref index);
+
+            var arg := args[index];
+            buffer.write(arg.toString());
+
+            chlen := 1
+         }
+         else
+         { 
+            buffer.write(ch); 
+            chlen := ch.Length;
+         };
+
+         i := i + chlen
+      };
+
+      ^ *buffer;
+   }
+}