Re: is lex useful?

kelley@phys.ocean.dal.ca says...
>So, my question is: if lex is useful, why isn't it used? Is there
>some snag (speed problems, perhaps, or difficult to port code?) that
>makes it smart to avoid lex?


Scott.Nicol@infoadvan.com (Scott Nicol) writes:
>The most common complaint is speed, but I don't think that is relevent in
>most applications. With a typical compiler (especially an optimizing
>compiler), scanning is among the cheapest components, consuming perhaps 5% to
>10% of the total compile time. Even if you bring the scan time down to 0,
>you have only speeded up the compiler 10%.


But it's probably a very cheap 10%. And if you sped the rest of the
compiler up, that scanning time is going to look more and more
attractive (eg speed rest of compiler up by factor of 2, now scanning
is nearly 20% of time). Of course, 10% is probably an overestimate for
a compiler that does a significant amount of work, as you've stated.


--
              Tyson Dowd
    trd@mundil.cs.mu.oz.au
http://www.cs.mu.oz.au/~trd
[For what it's worth, Ken Thompson's very fast Plan 9 C compiler hard coded
both the lexer and the parser for speed. -John]


--

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