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Jay Earley

Research and Advances Jan 1 1983

An efficient context-free parsing algorithm

A parsing algorithm which seems to be the most efficient general context-free algorithm known is described. It is similar to both Knuth's LR(k) algorithm and the familiar top-down algorithm. It has a time bound proportional to n3 (where n is the length of the string being parsed) in general; it has an n2 bound for unambiguous grammars; and it runs in linear time on a large class of grammars, which seems to include most practical context-free programming language grammars. In an empirical comparison it appears to be superior to the top-down and bottom-up algorithms studied by Griffiths and Petrick.

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Author Archives

Research and Advances Dec 1 1972

A method for incrementally compiling languages with nested statement structure

A method of incremental compilation is presented which applies especially to programming languages in which statements can be nested (such as Algol and PL/I). The method permits editing of the source language using a general purpose text editor, and incremental processing of changes without frequent recompilation of entire routines. The essential points of the method are: (1) the syntax of the language is restricted insofar as which constructs may occur on lines; (2) an internal data structure (called the skeleton) is maintained to represent the statement structure; (3) the recompilation is partially batched in the sense that recompilation of modified lines does not occur until the last of a set of editing commands has been received; and (4) the parsing and compilation are factored into two parts, that done on individual lines and that done globally to handle the relationships between the lines.
Research and Advances Oct 1 1971

Toward an understanding of data structures

This paper presents a notation and formalism for describing the semantics of data structures. This is based on directed graphs with named edges and transformations on these graphs. In addition, and implementation facility is described which could be part of a programming language, which allows a programmer who has expressed the semantics of an algorithm in terms of the graphs to then specify the implementation of some of his data structures in order to gain efficiency.
Research and Advances Oct 1 1970

A formalism for translator interactions

A formalism is presented for describing the actions of processors for programming languages—compilers, interpreters, assemblers—and their interactions in complex systems such as compiler-compilers or extendible languages. The formalism here might be used to define and answer such a question as “Can one do bootstrapping using a metacompiler whose metaphase is interpretive?” In addition an algorithm is presented for deciding whether or not a given system can be produced from a given set of component processors.
Research and Advances Feb 1 1970

An efficient context-free parsing algorithm

A parsing algorithm which seems to be the most efficient general context-free algorithm known is described. It is similar to both Knuth's LR(k) algorithm and the familiar top-down algorithm. It has a time bound proportional to n3 (where n is the length of the string being parsed) in general; it has an n2 bound for unambiguous grammars; and it runs in linear time on a large class of grammars, which seems to include most practical context-free programming language grammars. In an empirical comparison it appears to be superior to the top-down and bottom-up algorithms studied by Griffiths and Petrick.

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