@@ -20,12 +20,9 @@
 	immutable int    column;   /// 1-origin
 
 	mixin SimpleClass;
 	override string toString() const
-	{
-		return sprintf!("%s:%d:%d")(filename, lineno, column);
-	}
-
+		{ return sprintf!("%s:%d:%d")(filename, lineno, column); }
 	static LexPosition dummy;
 	static this(){ dummy = new LexPosition("<unnamed>",0,0); }
 }
 
@@ -53,16 +50,51 @@
 {
 	LexPosition pos;
 	this( LexPosition pos, string msg, string file=null, size_t line=0, Throwable next=null )
 	{
-		if(pos is null)
-			super(sprintf!("[??] %s")(msg), file, line, next);
-		else
-			super(sprintf!("[%s] %s")(pos, msg), file, line, next);
+		string fullmsg = pos is null ? sprintf!("\n[??] %s")(msg)
+		                             : sprintf!("\n[%s] %s")(pos, msg);
+		for(int i=0; i<callstack_pos.length || i<callstack_msg.length; ++i)
+		{
+			LexPosition p = (i<callstack_pos.length ? callstack_pos[i] : null);
+			string      m = (i<callstack_msg.length ? callstack_msg[i] : null);
+			fullmsg ~= p is null ? sprintf!("\n[??] %s")(m)
+		                         : sprintf!("\n[%s] %s")(p, m);
+		}
+		super(fullmsg, file, line, next);
 		this.pos = pos;
+	}
+	this( string msg, string file=null, size_t line=0, Throwable next=null )
+	{
+		this(null, msg, file, line, next);
 	}
 }
 
-class UnexpectedEOF : Exception { mixin ExceptionWithPosition; } /// EOF during lexing/parsing
-class LexException : Exception { mixin ExceptionWithPosition; } /// Lexer errors
-class ParseException : Exception { mixin ExceptionWithPosition; } /// Parser errors
+class UnexpectedEOF    : Exception { mixin ExceptionWithPosition; } /// EOF during lexing/parsing
+class LexException     : Exception { mixin ExceptionWithPosition; } /// Lexer errors
+class ParseException   : Exception { mixin ExceptionWithPosition; } /// Parser errors
 class RuntimeException : Exception { mixin ExceptionWithPosition; } /// Evaluator errors
+
+/// Per-thread call stack management.
+/// This scoped class's ctor&dtor maintain the callstack.
+/// TODO: make it "per-evaluator" !!!!!!!!!!!
+
+scope class PushCallStack
+{
+	this(LexPosition pos, string msg) { callstackEnterFunction(pos,msg); }
+	~this() { callstackLeaveFunction(); }
+}
+
+LexPosition[] callstack_pos;
+string[]      callstack_msg;
+
+private void callstackEnterFunction(LexPosition pos, string msg)
+{
+	callstack_pos ~= pos;
+	callstack_msg ~= msg;
+}
+
+private void callstackLeaveFunction()
+{
+	callstack_pos.length -= 1;
+	callstack_msg.length -= 1;
+}