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<Paper uid="E91-1012">
  <Title>Non-deterministic Recursive Ascent Parsing Ren~ Leermakers</Title>
  <Section position="9" start_page="0" end_page="0" type="concl">
    <SectionTitle>
8 Conclusions
</SectionTitle>
    <Paragraph position="0"> We established a very simple and elegant implementation of LR(0) parsing. It is easily extended to LALR(k) parsing by letting the functions \[q\] produce pairs with final items only after inspection of the next k input symbols. null The functional LR-parser provides a high-level view of LR-parsing, compared to conventional implementations.</Paragraph>
    <Paragraph position="1"> A case in point is the ubiquitous stack, that simply corresponds to the procedure stack in the functional case. As the proof of a functional LR-parser is not hindered by unnecessary implementation details, it can be very compact. Nevertheless, the functional implementation is as efficient as conventional ones. Also, the notion of memo-functions is an important primitive for presenting algorithms at a level of abstraction that can not be achieved without them, as is exemplified by this paper's presentation of both the recognizers and the parse forests.</Paragraph>
    <Paragraph position="2"> For non-LR grammars, there is no reason to use the complicated Tomita algorithm. If indeed non-deterministic LR-parsers beat the Earley algorithm for some natural language grammars, as claimed in \[4\], this is because the number of LR(0) states may be smaller than the size of IG for such grammars. Evidently, for the grammars examined in \[4\] this advantage compensates the loss of efficiency caused by the non-polynomiality of Tomita's algorithm. The present algorithm seems to have the possible advantage of Tomita's parser, while being polynomial.</Paragraph>
  </Section>
class="xml-element"></Paper>