flex and multiple inputs

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2 total messages Started by Andrew Thomas Thu, 19 Oct 1989 02:23

#512

Author: Andrew Thomas
Date: Thu, 19 Oct 1989 02:23

20 lines
1420 bytes

I have recently tried to write a parser using bison and flex.  It
worked fine on a single input file, but I wanted to read mulitple
files and parse them in the same way.  The program always aborted from
the parser on the second file saying that EOF had been reached.  I
tried setting yyin to a new file pointer before calling yyparse but it
did not help.  Eventually I changed the skeleton file to remove the
'static' definitions from the function 'yyrestart'.  Now from the
routine which calls yyparse, I set yyin to stdin (so yyrestart won't
try to close some other file), then call yyrestart with a pointer to
the file I want to read.  This has the desired effect, but now the
line number counting I have put in the .l file is off by the number of
lines in the previous file.   Is there a correct way to read multiple
input files with one parser run?

--

Andrew Thomas
andrewt@watsnew.waterloo.edu	Systems Design Eng.	University of Waterloo
"If a million people do a stupid thing, it's still a stupid thing." - Opus

Re: flex and multiple inputs

#518

Author: Vern Paxson
Date: Fri, 20 Oct 1989 15:41

34 lines
1553 bytes

In article <ANDREWT.89Oct18222337@watsnew.waterloo.edu> andrewt@watsnew.waterloo.edu (Andrew Thomas) writes:
> I have recently tried to write a parser using bison and flex.  It
> worked fine on a single input file, but I wanted to read mulitple
> files and parse them in the same way....
> Eventually I changed the skeleton file to remove the
> 'static' definitions from the function 'yyrestart'....
> This has the desired effect, but now the
> line number counting I have put in the .l file is off by the number of
> lines in the previous file.   Is there a correct way to read multiple
> input files with one parser run?

Yes.  What you want to do is add a rule like:

	<<EOF>>	{
		if there's another input file
			{
			fclose( yyin );
			yyin = fopen( file, "r" );
			reset line number counter
			YY_NEW_FILE;
			}
		else
			return;
		}

This is a new feature so it may be somewhat buggy.  If you have
problems with it, send me mail.

		Vern


	Vern Paxson			      vern@cs.cornell.edu
	Computer Science Dept.		      decvax!cornell!vern
	Cornell University		      vern@LBL (bitnet)

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