Re: is lex useful?

The moderator writes:


|> [The advantage of precomputing the state machine is that your lexer can run
|> a lot faster. AT&T lex is slow, but that's due to bad implementation. Flex
|> is quite fast, easily competitive with hand-written lexers. -John]


I'd be very surprised if it could compete with a lexer which just uses
a big switch on the character. And of course, once you know that the
next character is, e.g., alpha, there are very quick methods to scan
the rest.


On the other hand, I'm curious if anyone has looked into the
possibility of using mixed scanners. A quick switch on the first
character to catch the easy cases (symbols, white space to skip, etc.),
and the possibility of using regular expressions for the harder ones,
which hopefully don't occur as frequently in the source code.
--
James Kanze Tel.: (+33) 88 14 49 00 email: kanze@gabi-soft.fr
GABI Software, Sarl., 8 rue des Francs-Bourgeois, F-67000 Strasbourg, France
[The inner loop in a flex lexer is basically two table lookups, in the same
ballpark as a switch. -John]
--

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