parsing table

Now we can define exactly which rules will be contained where in the parsing table.

If the parsing table indicates that there is no such rule then it reports an error and stops.

Unfortunately, the First-sets are not sufficient to compute the parsing table.

The parsing table for this grammar looks as follows:

These codify the grammar of the language it recognizes and are typically called "parsing tables".

The parsing table instructs it to apply rule (1) from the grammar and write the rule number 1 to the output stream.

The parsing tables of the LR(1) parser are parameterized with a lookahead terminal.

Parsing Simulator This simulator is used to generate parsing tables LL(1) and to resolve the exercises of the book.

The construction of these parsing tables is based on the notion of LR(0) items (simply called items here) which are grammar rules with a special dot added somewhere in the right-hand side.

LR(1) parsing tables are constructed in the same way as LR(0) parsing tables with the modification that each Item contains a lookahead terminal.

In order to fill the parsing table, we have to establish what grammar rule the parser should choose if it sees a nonterminal 'A' on the top of its stack and a symbol 'a' on its input stream.

The parsing table instruction comes from the column headed by the input symbol '(' and the row headed by the stack-top symbol 'S'; this cell contains '2', which instructs the parser to apply rule (2).

Depending on how the parsing table is generated, these parsers can be called simple LR parsers (SLR), LALR parser (LALR), or canonical LR parsers.

If the top is a nonterminal then it looks up in the parsing table on the basis of this nonterminal and the symbol on the input stream which rule of the grammar it should use to replace it with on the stack.

The LALR parser and its alternatives, the SLR parser and the Canonical LR parser, have similar methods and parsing tables; their main difference is in the mathematical grammar analysis algorithm used by the parser generation tool.