LL(1) Conflict Resolution in a Recursive Descent Compiler Generator

Recursive descent parsing is restricted to languages whose grammars are LL(1), i.e., which can be parsed top-down with a single lookahead symbol. Unfortunately, many languages such as Java, C++, or C# are not LL(1). Therefore recursive descent parsing cannot be used or the parser has to make its decisions based on semantic information or a multi-symbol lookahead. In this paper we suggest a systematic technique for resolving LL(1) conflicts in recursive descent parsing and show how to integrate it into a compiler generator (Coco/R). The idea is to evaluate user-defined boolean expressions, in order to allow the parser to make its parsing decisions where a one symbol lookahead does not suffice. Using our extended compiler generator we implemented a compiler front end for C# that can be used as a framework for implementing a variety of tools.