flex (was Re: [HACKERS] Installation procedure.)

BTW, does anyone understand *why* our lexer files require flex and not
just garden-variety lex? Would it be worth trying to make them more
portable?

Some of the oldest and cruftiest AT&T lexers do not support the
concept of an exclusive start state, which we use extensively (it's my
fault; makes for *much* cleaner specifications).

Unfortunately, Sun adopted some SysV packages when they made the
switch from BSD, and got a bad lexer in the bargain. afaik, most other
systems ship a more capable package.

Or perhaps we should ship pre-lexed derived files, as we do for the
larger grammar files?

Yes, that would probably be a good idea...

- Thomas

--
Thomas Lockhart lockhart@alumni.caltech.edu
South Pasadena, California

"J. Michael Roberts" <mirobert@cs.indiana.edu> writes:

- I needed to install flex (no surprise) -- the instructions are quite
explicit, but, well, wrong: flex depends on bison. So you have to get
and compile bison first.

BTW, does anyone understand *why* our lexer files require flex and not
just garden-variety lex? Would it be worth trying to make them more
portable?

Can we do that? Is flex actually required too?

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  maillist@candle.pha.pa.us            |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

"J. Michael Roberts" <mirobert@cs.indiana.edu> writes:

- I needed to install flex (no surprise) -- the instructions are quite
explicit, but, well, wrong: flex depends on bison. So you have to get
and compile bison first.

BTW, does anyone understand *why* our lexer files require flex and not
just garden-variety lex? Would it be worth trying to make them more
portable?

Or perhaps we should ship pre-lexed derived files, as we do for the
larger grammar files?

Having to install bison & flex is probably the most annoying Postgres
prerequisite for people on non-Linux platforms, so I think it would
be nice to clean this up. I hadn't realized that you're essentially
forced to install both...

You undoubtedly already had both installed...

For the record, if configure doesn't find flex, it assumes lex. The
problem is if you don't even have lex.

However, the pre-lexed derived files are a good idea. If somebody then
really wants to mess with those, they can go get flex. That means that
the standard distribution *wouldn't* require flex. For me, it was a good
excuse to get the lead out and finally install flex and bison (OK, it took
me only about fifteen minutes, but you know how those to-do lists get).
But if my only goal were just to get Postgres running, that would be a
rather unnecessary step.

"J. Michael Roberts" <mirobert@cs.indiana.edu> writes:

For the record, if configure doesn't find flex, it assumes lex. The
problem is if you don't even have lex.

Or if you have lex but it doesn't work on Postgres' .l files, as indeed
is true for the vendor lex on HPUX, and probably some other systems.

However, the pre-lexed derived files are a good idea.

Yah. This has been discussed before, but no one has got round to it...

regards, tom lane