摘要 |
A description language (200) and a parser generator (202) for top-down parsers allows grammars for top-down parsers to be defined using a sequence of productions written as extended BNF expressions. For productions that are ambiguous, a lookahead construct in the grammar allows the programmer to specify an increased number of lookahead tokens. The lookahead construct can be specified on an expansion-by-expansion basis. As a result, the generated parser only maintains an increased number of lookahead tokens when required to process ambiguous productions. <IMAGE> |