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On the covering of left recursive grammars

A. Nijholt
1977 Proceedings of the 4th ACM SIGACT-SIGPLAN symposium on Principles of programming languages - POPL '77  
In this paper we show that on the elimination of left free grmar are not valid some prevailing ideas recursion in a context-An algorithm and a proof are given to show that every proper contextfree grammar  ...  is covered by a non-left-recursive grmar.  ...  We have to show L(G') = L(p), G' right-covers G and G' is non-left-recursive. In the algorithm a sequence of grammars is obtained in the following way.  ... 
doi:10.1145/512950.512959 dblp:conf/popl/Nijholt77 fatcat:rcuyo2pabncxxl3pgmykthjnba

On the covering problem for left-recursive grammars

Eljas Soisalon-Soininen
1979 Theoretical Computer Science  
Two new proofs of the fact that proper left-recursive grammars can be covered by non-left-recursive grammars are presented.  ...  The second proof involves a new method for eliminating kft recursion from a proper context-free grammar in such a way thyr the covering grammar is obtained directly.  ...  The project is headed by Professor Martti Tienari and sponsored by the Academy of Finland.  ... 
doi:10.1016/0304-3975(79)90052-5 fatcat:de5nng67xjgwpg4adge2zd5b2m

Cover results and normal forms [chapter]

Anton Nijholt
1977 Lecture Notes in Computer Science  
A cfg G is said to be left-recursive if there is at least one left-recursive nonterminal.  ...  In the secco~Iseetion we present some results and open problems on the covering of (arbitrary) cfg's by cfg's in GNF (Greibach normal form) and by cfg's in a non-left-recursive form.  ... 
doi:10.1007/3-540-08353-7_163 fatcat:cilai54thfgzlevpfg5r65vqva

Grammar functors and covers: From non-left-recursive to greibach normal form grammars

Anton Nijholt
1979 BIT Numerical Mathematics  
Attention is paid to structure preserving properties of transformations from a non-leftrecursive context-free grammar to a Greibach normal form grammar.  ...  It is demonstrated that such a transformation cannot only be ambiguity preserving, but also both cover and functor relations between grammars or their associated syntax-categories can be obtained from  ...  Despite this negative observation it is possible to obtain a CFG G' in GNF from a non-left-recursive grammar G in such a way that G' left covers G.  ... 
doi:10.1007/bf01931223 fatcat:7gmefptvqfd5pjteqvkjqvjog4

Structure preserving transformations on non-left-recursive grammars [chapter]

Anton Nijholt
1979 Lecture Notes in Computer Science  
Instead of arbitrary context-free grammars one can consider context-free grammars which conform to some requiremeqts on, for example, the form of the productions.  ...  The second part introduces a transformation from non-le~t-recursive grammars to grammars in Greibach normal form.  ...  The left port transformation which we display below is an one-step transformation, in the sense that each production of the new grammar is obtained in one step from the productions of the orlglnal grammar  ... 
doi:10.1007/3-540-09510-1_35 fatcat:wvvmquewerhmniu5hx4tjmgzj4

The representation of constituent structures for finite-state parsing

D. Terence Langendoen, Yedidyah Langsam
1984 Proceedings of the 22nd annual meeting on Association for Computational Linguistics -  
Both the representations and their interpretations can be computed from the expressions from left to right by finite-state devices.  ...  ABSTBACT A mixed prefix-postfix notation for representations of the constituent structures of the expressions of natural languages is proposed, which are of limited degree of center embedding if the original  ...  wherever G is right-recursive and is left-recursive wherever G is left-recursive.  ... 
doi:10.3115/980491.980498 dblp:conf/coling/LangendoenL84 fatcat:5txbgcdwk5hfnovexabrir5nqi

From left-regular to Greibach normal form grammars

A. Nijholt
1979 Information Processing Letters  
Acknowledgment I am grateful to the referees for some corrections and their suggestions regarding the presentation of these results.  ...  In the following definition of cover left parses are mapped on right parses. Definition 2.  ...  Moreover, it is possible to obtain a context-free grammar G" in Greibach normal form which right covers the left-regular grammar G (in this case right parses of G" are mapped on right parses of G).  ... 
doi:10.1016/0020-0190(79)90109-1 fatcat:hv63skz57zbatingsruiqvtwui

Structure preserving elimination of null productions from context-free grammars

Esko Ukkonen
1982 Theoretical Computer Science  
\ methotd is presented for the erhmi~ation of null productions from a context-fret grammar in such a way that the resulting grammar covers the original one, that is, the languages generated are the same  ...  and parses in the original grammar are homomorpikic irmages of equivalent parses in the covering grammar.  ...  If we want to construct a compatible cover in Greibach normal form for a left recursive grammar, it it, therefore necessar) to consider other cover types than the left covering. In this, ca!  ... 
doi:10.1016/0304-3975(82)90130-x fatcat:w677zzwtwbfa3ls7vepmxi7esi

A survey of normal form covers for context free grammars

Anton Nijholt
1980 Acta Informatica  
The emphasis in this paper is on the possibility of constructing e-free grammars, non-left-recursive grammars and grammars in Greibach normal form.  ...  All the cover results concerning the e-free grammars, the non-left-recursive grammars and the grammars in Greibach normal form are listed, with respect to several types of covers, in a cover-table.  ...  I would like to thank one of the referees for pointing out a few errors in the manuscript and for suggestions concerning the presentation of the results.  ... 
doi:10.1007/bf00264257 fatcat:hf5ttwu655espp6by6qo23fk2a

Page 3211 of Mathematical Reviews Vol. , Issue 80H [page]

1980 Mathematical Reviews  
Author’s summary: “Two new proofs of the fact that proper left- recursive grammars can be covered by non-left-recursive gram- mars are presented.  ...  The second proof involves a new method for eliminating left recursion from ~ proper context-free grammar in such a way that the covering grammar is obtained directly.”  ... 

Lexicalized context-free grammars

Yves Schabes, Richard C. Waters
1993 Proceedings of the 31st annual meeting on Association for Computational Linguistics -  
and dick ((~merl.coin Lexicalized context-free grammar (LCFG) is an attractive compromise between the parsing efficiency of context-free grammar (CFC) and the elegance and lexical sensitivity of lexicalized  ...  However, LCF(I supports much of the elegance of LTAG's analysis of English and shares with LTAG the ability to lexicalize CF(I;s without changing the trees generated.  ...  Acknowledgments We thank John Coleman who, by questioning whether the context-sensitivity of stochastic LTAG was actually being used for English, triggered this work.  ... 
doi:10.3115/981574.981591 dblp:conf/acl/SchabesW93 fatcat:kkn2jazaibclbcpgqocizqdege

Left recursion in Parsing Expression Grammars

Sérgio Medeiros, Fabio Mascarenhas, Roberto Ierusalimschy
2014 Science of Computer Programming  
A frequently missed feature of PEGs is left recursion, which is commonly used in Context-Free Grammars (CFGs) to encode left-associative operations.  ...  We present an extension to the semantics of the operations of this parsing machine that let it interpret left-recursive PEGs, and prove that this extension is correct with regards to our semantics for  ...  is possible to transform the parse tree of the non-left-recursive grammar into the left-associative parse tree of the left-recursive grammar.  ... 
doi:10.1016/j.scico.2014.01.013 fatcat:p2js53pasjblflvxtdkixch7m4

Left Recursion in Parsing Expression Grammars [chapter]

Sérgio Medeiros, Fabio Mascarenhas, Roberto Ierusalimschy
2012 Lecture Notes in Computer Science  
We prove the conservativeness of these extensions, and also prove that they work with any left-recursive PEG.  ...  A frequently missed feature of PEGs is left recursion, which is commonly used in Context-Free Grammars (CFGs) to encode left-associative operations.  ...  is possible to transform the parse tree of the non-left-recursive grammar into the left-associative parse tree of the left-recursive grammar.  ... 
doi:10.1007/978-3-642-33182-4_4 fatcat:fa4yunugebfbdnvfiao4m5vjsi

Guarded attribute grammars

Richard A. Frost
1992 SIGPLAN notices  
of grammars containing left-recursive productions.  ...  The use of a topdown parsing strategy increases modularity and the use of left-recursive productions facilitates specification of semantic equations.  ...  reflect the structure of grammars containing left-recursive productions.  ... 
doi:10.1145/130981.130990 fatcat:vmnqcjrr2jdidcdj3le4iuur2m

Guarded attribute grammars

R. A. Frost
1993 Software, Practice & Experience  
of grammars containing left-recursive productions.  ...  The use of a topdown parsing strategy increases modularity and the use of left-recursive productions facilitates specification of semantic equations.  ...  reflect the structure of grammars containing left-recursive productions.  ... 
doi:10.1002/spe.4380231006 fatcat:wvekcvwh7fcgllyjbnp6mq776a
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