lex & yacc

[lexslave]

hi there,

i would like to install lex & yacc into my fedora12 o.s.

¿does anyone know the steps?







cheers

[aleph]

The GNU implementation of lex/yacc is called "flex" and "bison" respectively. Just grab them from the repository and you're done.

yum install flex bison

There's also byacc, the BSD yacc, in the repo.

[lexslave]

Originally Posted by aleph

The GNU implementation of lex/yacc is called "flex" and "bison" respectively. Just grab them from the repository and you're done.

yum install flex bison

There's also byacc, the BSD yacc, in the repo.

yum install flex bison has to be typed like this inside the terminal window?

i mean - yum install flex - installs flex only?

[dd_wizard]

Yes, "yum install flex bison" gets both unless one is a dependency.

dd_wizard

[lexslave]

Originally Posted by dd_wizard

Yes, "yum install flex bison" gets both unless one is a dependency.

dd_wizard

and it did once i connected to the internet. thanks.


now there's more:


now i'm trying to create my C file by doing:
-flex example.l-
this step works with no problem. it creates the
file lex.yy.c properly.


but when i do
'gcc lex.yy.c -lfl -o program '

says
- bash: gcc: command not found -








S.O.S

[dd_wizard]

I see flex, byacc, and bison in the repos.

dd_wizard

---------- Post added at 04:44 PM CDT ---------- Previous post was at 04:43 PM CDT ----------

Your way to fast, aleph!

[jpollard]

Note: there are some differences between the old yacc/bison and lex/flex
utilities. Yacc only allows a single parser, bison allows multiple. These differences
carry on into lex/flex. These changes are present in the input files and are make
bison/flex source incompatible with yacc/lex.

[RupertPupkin]

You can use either the -l or -X option to force maximum compatibility with traditional lex or POSIX lex, respectively. There is a similar option (-y) to make bison compatible with yacc.

[jpollard]

These make it more "upwardly" compatible, but there are a few things that
are still a bit different. Most usage is accepted that way, but a full compiler
specification will likely fail without some tweaking.

[Hlingler]

Have you by any chance installed gcc ? Or any of the compilers or development tools ? Just install the whole pile, and be done with it:
su
yum groupinstall "Development Tools" "Development Libraries"

V

[lexslave]

ok



i have tried it before doin' the
- yum install flex -

and before doing the
- gcc lex.yy.c -lfl -o program -



and the first one, "groupinstall Development Tools" gives an interminable number of
read/write errors while doing the 'transaction' (final part of install).

same with "Development Libraries" it outputs some kind of error as well.




count that i'm using Fedora booting from a usb external device.


¿any solution?
¿would change anything to boot from hard drive?

[aleph]

the Dev Tools group contains a huge amount of software and *****. Perhaps you had your disk space run out before the install completed.

[Hlingler]

Post the full output of the errors so that we don't have to guess what's wrong. Or just install the bare minimum compilers:
su
yum install gcc gcc-c++

But it would be best to find out what went wrong: if, as Aleph guesses, you ran out of disk space, that is a bad thing.

V

[lexslave]

Originally Posted by Hlingler

Post the full output of the errors so that we don't have to guess what's wrong. Or just install the bare minimum compilers:
su
yum install gcc gcc-c++

But it would be best to find out what went wrong: if, as Aleph guesses, you ran out of disk space, that is a bad thing.

V

that worked out!.


now doing my output and last file:

gcc lex.yy.c –lfl –o program


(with -lfl command to link with flex library).




but how can i input a file to the executable 'program'.

Since by typing only the word 'program' all alone it shows up that is not a command.

---------- Post added at 10:03 PM CDT ---------- Previous post was at 06:08 PM CDT ----------

anybody home?

[jpollard]

If you are attempting to develop a small language, you really need to get
a good bit of background on the interaction between flex, bison, and applications...

Flex is used to generate C code (or C++) for a scanner from a specification file.

Bison is used tp generate C code (or C++) for a parser from a specification file.

As a side effect, the generated C/C++ allows for a parser that may use a scanner
from flex or a hand crafted scanner.

None of this goes on to address the application (whether a data processing
application or a compiler).

After compiling all source files (scanner - which may have multiple files, parser -
which again may/will have multiple files, and application - still more source files)
the final executable is generated with the system linker. This is invoked either
directly, or as part of the C/C++ compiler sequence. This usually involve make,
and a lot of libraries (which is why the program development group install is so
useful).

Some of your questions indicate the lack of a development background - I suggest
the textbook "lex & yacc, Second Edition"

(http://oreilly.com/catalo /9781565920002)

which has a number of examples that will help. Besides, I found that the subject is
sufficiently complex that I refer back to it whenever I start another such project. I
just don't remember all of the nuances to the subject.

One of the reasons I prefer flex/bison over lex/yacc is that I sometimes have
situations where I may be scanning/parsing two different files, or the same file
with sections containing different languages... requiring two or more parsers
and scanners. flex/bison allows for this, lex/yacc does not. Flex/Bison are
also more portable in that flex/bison run on more platforms than does lex/yacc.