An Extension Of The Unit Production Elimination Algorithm

Removing unit productions from LR parsing machines can reduce the space and time cost of parsing. The unit production elimination algorithm of Pager may result in redundant states in the generated parsing machine. This work introduces an extension to remove the redundancy and thus minimize the parsing machine. We implemented the unit production elimination algorithm and its extension algorithm into the Hyacc parser generator. We study its performance and discuss relevant issues here. Theoretical analysis and experiement result show that when the extension is used, the parser generation process uses the same amound of memory, but more processing time. The resulted parsing machine can be much more compact.