Syntax Analysis: The Left-Most-Derivation-and-Reduction Trees and its Compare with the LR Parsing Methods

A new syntax analysis method is presented, called as “left-most-derivation-and-reduction trees.” With the new way, the syntax analysis is carried out under the direction of the syntax trees, while in the traditional syntax analysis, the syntax tree is obtained when the analysis has finished. Furthermore, through the point of view of the “left-most-derivation-and-reduction trees”, the properties of the LR parsing method is newly surveyed and explained in an easier, simpler, and more directed way. Finally, the new way is expected to get further development in future.

An LR Parser with Less States

This paper presents a new construction method of LR parser which is based on the theory of deterministic finite automata. The deterministic infinite automata are simplified for obtaining the LR parsing table with fewer states by merging the equivalent states. The new construction method has the same reorganization power as LALR parser but avoids the “reduce/reduce” conflict in LALR method. The experiment results show that the number of states in parsing table can be reduced greatly if the proposed method is used.