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<Paper uid="C86-1125">
  <Title>ON FORMALIZATIONS OF MARCUS' PARSER</Title>
  <Section position="7" start_page="534" end_page="534" type="concl">
    <SectionTitle>
6. Conehlsion
</SectionTitle>
    <Paragraph position="0"> We have shown that the class of context-free grammars parsablc by a Marcus-type parser is neither a subcla,;s of l,R(k,t) nor a subclass of BCP(m,n) grammars. We have introduced I,P, RL(k) grammars, which formalize the concepts of Marcus parsing in a purely bottom-up parser. One may consider the lookahcad policy used in basic I,RRL(k) grammars as the opposite extreme to lhc one employed in l,R(k) grammars. In 1.R(k) parsing the lowest level of nodes, i.e., terminals are used as lookaheads, while in basic I,RRL(k) parsing the highest level nodes that follow the current construct act as lookaheads. A modified version of these grammars combines the two policies. The most general class of I,RRL(k) grammars which is defined in \[5\] considers lookaheads at arbitrary levels. It can be shown that for a fixed k, this class of grammars is the largest known class that generalizes the concepts of LR(k) parsing while retaining the property that membership of an arbitrary grammar in the class is still decidable.</Paragraph>
    <Paragraph position="1"> At'knowiedgemeuts The author is indebted to I)r. L,K. Schnberl for his suggestions and carehd review of the draft of this paper. The research was supported by tile Natural Sciences and Engineering Research Council of Canada Qperating Grant A8818 under Dr. SchubcWs supervision,</Paragraph>
  </Section>
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