>>1
Not exactly, you can represent the AST of an expression using exactly the same code as the expression (with a quote). You can also manipulate it very easily. In other languages, the AST is a lot messier, but with a parser you can get at it. The difference lies in the amount of difficulty you'd have in generating code or modifying code. It's just a lot easier in a homoiconic language (for example some Lisps).