/// if the variable name is in current table, return Identifier itself,
/// which contains the real value.
/// else return a reference to ancient identifier tables' identifiers.
/// will break if we can't find any.
public MRef Search(string name, int line = -1, int column = -1)
{
if (name == "")
{
throw new LogicException("Cannot deal with empty string!", line, column);
}
if (TryGetValue(name, out MRef v))
{
return(v);
}
else
{
if (parent == null)
{
throw new LogicException(
"Cannot find identifier : " + name,
line, column
);
}
else
{
return(parent.Search(name, line, column));
}
}
}
public override MValue Eval(IdentifierTable t)
{
// This will return the reference of a variable.
return(t.Search(identifier, line, col).target);
}