Re: [TUHS] v7 K&R C [really lexers]

[Jon Steinhart <jon@fourwinds.com>]

Steffen Nurpmeso writes:
> Tony Finch wrote in
> <alpine.DEB.2.20.2005142316170.3374@grey.csi.cam.ac.uk>:
>  |Larry McVoy <lm@mcvoy.com> wrote:
>  |>
>  |> It's got some perl goodness, regexps are part of the syntax, ....
>  |
>  |I got into Unix after perl and I've used it a lot. Back in the 1990s I saw
>  |Henry Spencer's joke that perl was the Swiss Army Chainsaw of Unix, as a
>  |riff on lex being its Swiss Army Knife. I came to appreciate lex
>  |regrettably late: lex makes it remarkably easy to chew through a huge pile
>  |of text and feed the pieces to some library code written in C. I've been
>  |using re2c recently (http://re2c.org/), which is differently weird than
>  |lex, though it still uses YY in all its variable names. It's remarkable
>  |how much newer lexer/parser generators can't escape from the user
>  |interface of lex/yacc. Another YY example: http://www.hwaci.com/sw/lemon/
>
> P.S.: i really hate automated lexers.  I never ever got used to
> use them.  For learning i once tried to use flex/bison, but
> i failed really hard.  I like that blood, sweat and tears thing,
> and using a lexer seems so shattered, all the pieces.  And i find
> them really hard to read.
>
> If you can deal with them they are surely a relief, especially in
> rapidly moving syntax situations.  But if i look at settled source
> code which uses it, for example usr.sbin/ospfd/parse.y, or
> usr.sbin/smtpd/parse.y, both of OpenBSD, then i feel lost and am
> happy that i do not need to maintain that code.
>
> --steffen

Wow, I've had the opposite experience.  I find lex/yacc/flex/bison really
easy to use.  The issue, which I believe was covered in the early docs,
is that some languages are not designed with regularity in mind which makes
for ugly code.  But to be fair, that code is at least as ugly with hand-crafted
code.

I believe that the original wisecrack was directed towards FORTRAN.  My ancient
experience was that it was using lex/yacc for HSPICE was not going to work so I
had to hand-craft code for that.

Jon