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Top-Down Parsing Language (TDPL) is a type of analytic formal grammar developed by Alexander Birman in the early 1970s in order to study formally the behavior of a common class of practical top-down parsers that support a limited form of backtracking. Birman originally named his formalism ''the TMG Schema'' (TS), after TMG, an early parser generator, but the formalism was later given the name TDPL by Aho and Ullman in their classic anthology ''The Theory of Parsing, Translation and Compiling''. == Definition of a TDPL grammar == Formally, a TDPL grammar ''G'' is a tuple consisting of the following components: * A finite set ''N'' of ''nonterminal symbols''. * A finite set Σ of ''terminal symbols'' that is disjoint from ''N''. * A finite set ''P'' of ''production rules'', where a rule has one of the following forms: * * ''A'' ← ε, where ''A'' is a nonterminal and ε is the empty string. * * ''A'' ← ''f'', where ''f'' is a distinguished symbol representing ''unconditional failure''. * * ''A'' ← ''a'', where ''a'' is any terminal symbol. * * ''A'' ← ''BC/D'', where ''B'', ''C'', and ''D'' are nonterminals. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Top-down parsing language」の詳細全文を読む スポンサード リンク
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