Diagnostics on LALR(k) conflicts based on a method for LR(k) Testing

A user of an LALR(k) parser generator system may have difficulties in understanding how a given LALR(k) conflict is generated. This is especially difficult if the conflict does not correspond to an LR(k) conflict.A practical method for giving informative diagnostics on LALR(k) conflicts is presented. The diagnostics distinguish between those LALR(k) conflicts that correspond to LR(k) conflicts and those that do not. As a side effect the user is thus informed whether or not his grammar is in fact LR(k) despite not being LALR(k).The method is based on an algorithm for testing LR(k)-ness using the LR(0) machine supplied with LALR(k) lookahead sets. This algorithm is presented and its correctness is proved.