Editing Canonical LR parser (section)

=== Goto ===
The lookahead of an LR(1) item is used directly only when considering reduce actions (i.e., when the • marker is at the right end).

The '''core''' of an LR(1) item [S → a A • B e, c] is the LR(0) item S → a A • B e. Different LR(1) items may share the same core.

For example, in item set 2

: [E → T •, $]
: [T → T • + n, $]
: [T → T • + n, +]

the parser is required to perform the reduction [E → T] if the next symbol is '$', but to do a shift if the next symbol is '+'. Note that a LR(0) parser would not be able to make this decision, as it only considers the core of the items, and would thus report a shift/reduce conflict.

A state containing [A → α • X β, a] will move to a state containing [A → α X • β, a] with label X.

Every state has transitions according to Goto.