The following is an update of the comp.compilers article
"CEX - Context-Free Expression Filter"
2007 February 25
https://compilers.iecc.com/comparch/article/07-02-067
Both an updated and UTF-8 converted version of the original have been
posted under comp.theory here:
https://groups.google.com/g/comp.theory/c/JTnm83_tWcA
The following cites from the original have been updated:
In 1993, the regular expression filter REX was introduced. Notable
amongst its features was that processing was carried out entirely
within an algebraic paradigm. The utility and the algorithms
underlying it have eventually found their way into other applications
(e.g. XML-Query).
This was originally in the comp.compilers archive. The latest updates
may now be found at GitHub under
https://github.com/RockBrentwood/RegEx
CEX is the long-planned successor to REX. It will not handle the full
range of REX functionality, but will process language expressions at
the next stage up the Chomsky hierarchy: Context-Free Expressions.
The Untold Story of Formal Languages >http://federation.g3z.com/CompSci/index.htm#Untold
(Numerous other references may be found on this page, both above and
below this link)
Currently linked at:
https://web.archive.org/web/20080106150352/http://federation.g3z.com/CompSci/ index.htm#Untold
Descriptions only are available, not the PDF's; and has been largely
subsumed both by the following and publications recent and pending
listed in the references (cited in the comp.theory article):
The Algebraic Approach II-V
https://www.scribd.com/document/235317956/The-Algebraic-Approach-II-V
The new framework for context-free expressions, which is part of a new algebraic foundation for formal language and automata theory laid out
in recent publications and elsewhere, is a descendant of the algebraic formulation published in 1963 by Chomsky and Schützenberger.
A follow-up note to the 2018 papers that I sent both directly to
Chomsky and as an open letter on the recent developments is here:
https://www.scribd.com/document/392094748/The-evolution-of-recent-development s-in-formal-language-theory-from-the-1960-s
An early draft of the presentation for one of the recent publications
may be found here:
Co Equalizers and Tensor Products for Idempotent Semirings
https://www.scribd.com/document/392094657/Co-Equalizers-and-Tensor-Products-f or-Idempotent-Semirings
More details may be found in the comp.theory article.
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