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Suan Yeo | 1 Jul 00:38

Parsing across multiple buffers and maintaining state (prefably without additional memory usage)

I'm trying to search for a particular string within a chain of buffers, say,
"sausage". Right now, it works fine if "sausage" is wholly in one buffer, but if
it is split between 2 buffers, eg, {"........sau", "sage........", ...}, flex
does not match it. This is my current implementation:

while (buf)
{
  buf_state = yy_scan_bytes(...);
  result = yylex();
  yy_delete_buffer(buf_state);
  buf = buf->next;
}

I use yy_scan_bytes because as I understand it does not copy it into a new
buffer (ie. scans in-place). How should I change my implementation to achieve
the above (other than copying everything into a single buffer)?
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Yu-zhong shen | 23 Feb 03:33

Help! How to use unicode in flex?

I am working with flex in GNUWin32.

I want to process some unicode text with it.

Is there any option or patch of flex that support the unicode?

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孟伟超 | 31 Dec 11:01
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Excuse me

I want a flex
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Georg.Tenckhoff | 29 Apr 10:19
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(no subject)

Hallo everybody,

is there any trick to convince flex to auto-complete options entered e.g. from stdin? Posed the same
question differently: Can I access the flex parse tables as a kind of tree structure indicating which
characters are allowed to follow as branches?

Freundliche Grüße / Kind regards

Georg Tenckhoff
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lookthree | 27 Jan 22:13

Help please

Hi,
I'm a new Flex user.
I'm having the follow problem:

1. I've created one file Example.l:

%option c++
%option yylineno
%option noyywrap
%option caseless

delim [ \t\n]
ws {delim}+
letter [A-Za-z]
digit [0-9]
id {letter}({letter}|{digit})*
number {digit}+(\.{digit}+)?(E[+\-]?{digit}+)?

%%
            int yylval;
{ws}        {;}
if          { return(IF);}
then        { return(THEN);}
else        { return(ELSE);}
{id}        { return(ID);}
{number}    { return(NUMBER);}
"<"         { yylval = LT; return(RELOP);}
"<="        { yylval = LE; return(RELOP);}
"="         { yylval = EQ; return(RELOP);}
"<>"        { yylval = NE; return(RELOP);}
">"         { yylval = GT; return(RELOP);}
">="        {yylval = GE; return(RELOP);}
.           {return(ERROR);}
%%


and i've run >Flex example.l

and it has returned the file lex.yy.cc.

2. Well, i've created also the main program in c++, let's call it main_prog.cpp:



#include <stdio.h>
#include <ctype.h>
enum {LT, LE, NE, GT, GE, EQ, IF, THEN, ELSE, ID, NUMBER, RELOP, ERROR};
#include <FlexLexer.h>
#include "lex.yy.cc"

int main(int argc, char *argv[])
{
    int token;
    FlexLexer* lexer = new yyFlexLexer();
    while ((token=lexer->yylex()) != 0) {
        switch (token) {
        case RELOP: printf("%s","RELOP"); break;
        case NUMBER: printf("%s","NUMBER"); break;
        case ID: printf("%s","ID"); break;
        case IF: printf("%s","IF"); break;
        case THEN: printf("%s","THEN"); break;
        case ELSE: printf("%s","ELSE");break;
        case ERROR: printf("%s", "illegal character"); break;
        default:
                    printf("%s","UNKNOWN");
                    break;
        }
        printf("%s\n", lexer->YYText());
    }
    return 0;
}

The problem becomes when I compile it using

        g++ main_prog.cpp -o main_prog

,infact the system answer me with:

/usr/include/FlexLexer.h:113: error: redefinition of ‘class yyFlexLexer’
/usr/include/FlexLexer.h:113: error: previous definition of ‘class yyFlexLexer’

thank you for helping me,

Simone.










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Eric Fowler | 8 Sep 04:25

Flex empty string

I hear a rumor this is the place for online flex discussion.

I am a relative newbie and I want to match NMEA 0183 strings coming from a GPS.

They look like this:
$GPGGA,123519,4807.038,N,01131.000,E,1,08, 0.9,545.4,M,46.9,M,,*47

except when they look like this:

$GPGGA,123519,4807.038,N,01131.000,E,,,,,,,,,*47

In other words, many fields can be blank, but they are always comma - delimited. When they exist they are nicely structured, e.g. {DIGIT}{4}"."{DIGIT}{3} matches a latitude string.

So how do I distinguish between a field with some specific data and a delimiter, and an empty string followed by the same delimiter?

Thanks.

Eric

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Carlos Smith | 2 Jun 15:47

Building flex-2.5.34 from CVS

Hi,

Just want to confirm i succesfully build
flex 2.5.34 fresh from cvs.

The README.cvs says to use

gettext 0.14.5, but it does not work.
Instead you needs gettext-devl (for autopoint)

Also, is ident 2.8 the correct version.
May be it is 2.2.8 ?

-- carlos
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harsh | 31 May 08:11

warning

Hi,

 

I get a warning dealing with "yy_flex_realloc" saying that:'void* yy_flex_realloc(void*, yy_size_t)' defined but not used,

I would like to know how it's posssible to avoid it.

 

Best regards,

Harsh

 

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post2li | 29 May 13:09
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Flex/Bison Segment Fault?

I am trying to test the code in the book "Lex & Yacc, 2nd", however,
it didn't work as described. Pls.

# uname -a
Linux redhat9 2.4.20-8 #1 Thu Mar 13 17:54:28 EST 2003 i686 i686 i386
GNU/Linux

# flex -V
flex version 2.5.4

# bison -V
bison (GNU Bison) 1.35

# flex -olexa.yy.c ch1-05.l
# bison -obisa.tab.c ch1-05.y
# gcc -o ex bisa.tab.c lexa.yy.c -ll

# ./ex
Segmentation fault
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kkc | 25 May 18:34
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lex & yacc, Second Edition example compile code problem


I try compile all code using "make" command in linux, but it come back with
compile error, please help.

thank you!

/* output
[work]$ make
flex ch1-01.l
mv lex.yy.c ch1-01.c
gcc -g -o ch1-01.pgm ch1-01.c -ly -ll
/usr/bin/ld: cannot find -ly
collect2: ld returned 1 exit status
make: *** [ch1-01.pgm] Error 1
[work]$

*/
--

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arun kv | 30 Apr 12:54
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memory errors ....

  
Hi All, 

I have implemented a parser using lex and yacc ,  my lex and yacc files are named parser.y and scanner.l 
(these files are compiled with flex++ and bison++  to make my parser compatible with C++) 
My parser is working fine but .... 
The issue is when I run my parser with purify (a memory detection tool ) .It gives out memory errors in the flex
and bison generated  source codes (parser.cpp , parser.h and scanner.h )

The purify errors for the parser are : 
IPR :Invalid pointer read , IPW :Invalid pointer write , BSR: Beyond stack read error 
Shown by these variables in parser.cpp 
yystate
yyn    
yyssp  
yyvsp  
yyerrstatus    
yycharl

For detailed purify log please see the attached file. 
What I want to know is that, Is there any way in which I can control these variables form my lex and yacc files. 
Or how else I can fix these memory errors shown by purify. 
Best Regards 
Arun
Attachment (parser.log): application/octet-stream, 41 KiB
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