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SLE 2019
Sun 20 - Fri 25 October 2019 Athens, Greece
co-located with SPLASH 2019
Mon 21 Oct 2019 16:00 - 16:30 at Templars - Session 4: Parsing Chair(s): Adrian Johnstone

We consider the possibility of making the lexicalisation phase of compilation more powerful by avoiding the need for the lexer to return a single token string from the input character string. This has the potential to empower language design by softening the boundaries between lexical and phrase level specification. The large number of lexicalisations makes it impractical to parse each one individually, but it is possible to share the parsing of common subparts, reducing the number of tokens parsed from the product of the token numbers associated with the components to their sum. We report total numbers of lexicalisations of example Java strings, and the impact on these numbers of various lexical disambiguation strategies, and we introduce a new generalised parsing technique that can efficiently parse multiple lexicalisations of character string simultaneously. We then use this technique on Java, reporting on the number of lexicalisations that correspond to syntactically correct Java strings and the degree to which the standard Java lexer is safe in the sense that it does not remove all the syntactically correct lexicalisations of an input character string. Our multi-lexer parser is an alternative to scannerless parsing of a character level grammar, retaining the separation between grammar terminals and the corresponding lexical tokens. This has the advantages of allowing the parser to use terminal level lookahead and keeping lexical level disambiguation separate from the context free grammar.

Mon 21 Oct
Times are displayed in time zone: Beirut change

16:00 - 17:30
Session 4: ParsingSLE 2019 at Templars
Chair(s): Adrian JohnstoneRoyal Holloway, University of London
Multiple Lexicalisation - A Java Based Study
SLE 2019
Elizabeth ScottRoyal Holloway University of London, Adrian JohnstoneRoyal Holloway, University of London
Breaking Parsers: Mutation-based Generation of Programs with Guaranteed Syntax ErrorsNEW IDEABest Paper
SLE 2019
Moeketsi RaselimoStellenbosch University, Jan TaljaardStellenbosch University, Bernd FischerStellenbosch University
Default disambiguation for online parsers
SLE 2019
Lukas DiekmannKing's College London, Laurence TrattKing's College London
DOI Pre-print