CSCE 434 Lecture 20

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Lecture Slides

Building a SLR parser

Canonical LR(0) items

Kernel items: all items with cursor at left end of RHS, with addition of a rule $[S^{\prime }::=\cdot S]$.

$S^{\prime }::=S$ is a production in the augmented grammar $G^{\prime }$ mapping a new start state $S^{\prime }$ to the start state of a grammar $G$.

We do this because we cannot have an "initial" item $\cdot S$ or final item $S\cdot$ in the original grammar (nothing goes to $S$)

$I$: set of items; take its closure (all possible items reachable from the current state)