Vaughan Pratt presented "Top Down Operator Precedence" at the first annual Principles of Programming Languages Symposium in Boston in 1973. In the paper Pratt described a parsing technique that combines the best properties of Recursive Descent and Floyd's Operator Precedence. It is easy to use. It feels a lot like Recursive Descent, but with the need for less code and with significantly better performance. He claimed the technique is simple to understand, trivial to implement, easy to use, extremely efficient, and very flexible. It is dynamic, providing support for truly extensible languages.
Oddly enough, such an obviously utopian approach to compiler construction is completely neglected today. Why is this? Pratt suggested in the paper that a preoccupation with BNF grammars and their various offspring, along with their related automata and theorems, has precluded development in directions that are not visibly in the domain of automata theory.
