Re: Is this a new idea?

>[Scanning and parsing can be as much as half of the total time that a
>compiler takes (so says Ken Thompson of his Plan 9 C compiler) and that is
>quite amenable to incremental precalculation. -John]


Although the Plan 9 compiler is a very interesting design and the paper on
it is very much worth reading, some of the comments need to be taken with
a grain of salt. He isn't doing ambitious optimization (note that he
ignores `volatile' entirely), which will surely influence the distribution
of time among phases.


I also recall a case (not a compiler and not Ken Thompson) where an
authoritative claim was made that a precompiled binary format was
necessary because re-reading the text file each time was too slow... and
on examination this appeared to be mostly the result of an input parser
written so ineptly that it bordered on incompetence. For the code I had
to write, I ignored the precompiled binary -- its format was complicated
and inconvenient -- and re-read the text file. The performance impact was
unnoticeable.
--
Henry Spencer @ U of Toronto Zoology, henry@zoo.toronto.edu utzoo!henry
--

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