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[[Category:WG211]]

<h1>Verifiable Composition of Grammars</h1>

<h3>August Schwerdfeger and Eric Van Wyk</h3>

Abstract:

One challenge in extensible languages arises in the composition of the
concrete syntax specifications for a host language and a collection of
(domain-specific) language extensions. For this talk, these
specifications consist, as is to be expected, of context-free grammars
with each terminal symbol mapped to a regular expression, from which a
slightly-modified LALR(1) parser and context-aware scanner are
generated. Traditionally, conflicts are detected in the parse-table
of the composed grammar when it is constructed, but this comes too
late as it may be a non-expert programmer that directs the language
tools to compose an eclectic set of language extensions chosen by the
programmer for a particular task.

In this talk we discuss a modular analysis that is performed
independently by each extension designer on her extension (composed
alone with the host language). If each extension passes this modular
analysis, then the language composed later by the non-expert
programmer will compile with no conflicts or lexical ambiguities.
Thus, extension writers can verify that their extension will safely
compose with others and, if not, fix the specification so that it
will. This is possible due to the context-aware scanner's lexical
disambiguation and a set of reasonable restrictions limiting the sort
of constructs that can be introduced by a language extension. The
restrictions ensure that the states in the parse table can be
partitioned so that each state can be attributed to the host language
or a single language extension.

* [[Media:vanwyk-wg09.pdf | vanwyk-wg09.pdf ]]: Slides

==File Attachments==

*[[Media:vanwyk-wg09.pdf | vanwyk-wg09.pdf]]

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