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Re: Very Fast: Directly Coded Lexical Analyzer
- From: Robert Dewar <dewar at adacore dot com>
- To: Ronny Peine <RonnyPeine at gmx dot de>
- Cc: gcc at gcc dot gnu dot org
- Date: Fri, 10 Aug 2007 07:49:18 -0400
- Subject: Re: Very Fast: Directly Coded Lexical Analyzer
- References: <998d0e4a0705311334w7eba684cwcfe1ed70c4b63add@mail.gmail.com> <20070601072828.236560@gmx.net> <200706011226.49596.RonnyPeine@gmx.de>
Ronny Peine wrote:
Hi,
my questions is, why not use the element construction algorithm? The Thomson
Algorithm creates an epsilon-NFA which needs quite a lot of memory. The
element construction creates an NFA directly and therefor has fewer states.
Well, this is only interesting in the scanner creation which is not so
important than the scanner itself, but it can reduce the memory footprint of
generator. It's a pity i can't find a url for the algorithmdescription, maybe
i even have the wrong naming of it. I have only read it in script Compiler
Construction at the University.
To me, very fast (millions of lines a second) lexical analyzers are
trivial to write by hand, and I really don't see the point of tools,
and certainly not the utility of any theory in writing such code.
If anything the formalism of a finite state machine just gets in the
way, since it is more efficient to encode the state in the code
location than in data.