[RESOLVED] flex "flex scanner push-back overflow"
flex is happy when i run "flex scanner.l", but returns the error "flex scanner push-back overflow" when i run "flex new_scanner.l"
here are the files:
scanner.l:
Code:
/* scanner for a toy Pascal-like language */
%{
#include <math.h> /* needed for call to atof() */
%}
DIG [0-9]
ID [a-z][a-z0-9]*
%%
{DIG}+ printf("Integer: %s (%d)\n", yytext, atoi(yytext));
{DIG}+"."{DIG}* printf("Float: %s (%g)\n", yytext, atof(yytext));
if|then|begin|end printf("Keyword: %s\n",yytext);
"(" printf("Open paren\n");
")" printf("Close paren\n");
{ID} printf("Identifier: %s\n",yytext);
"+"|"-"|"*"|"/" printf("Operator: %s\n",yytext);
">"|"<" printf("Relational operator: %s\n",yytext);
"{"[^}\n]*"}" /* skip one-line comments */
[ \t\n]+ /* skip whitespace */
. printf("UNRECOGNIZED: %s\n",yytext);
%%
main(){ yylex(); }
new_scanner.l:
Code:
/* scanner for a toy Pascal-like language */
%{
#include <math.h> /* needed for call to atof() */
%}
DIG [0-9]
ID [a-z][a-z0-9]*
VAL {DIG}+"."?{DIG}*|{ID}
SP [ \t\n]*
EXP {EXP}{SP}("+"|"-"|"*"|"/"){SP}{VAL}|{VAL}
%%
{EXP}{SP}(">"|"<"){SP}{EXP} printf("Conditional: %s\n", yytext);
{DIG}+ printf("Integer: %s (%d)\n", yytext, atoi(yytext));
{DIG}+"."{DIG}* printf("Float: %s (%g)\n", yytext, atof(yytext));
if|then|begin|end printf("Keyword: %s\n",yytext);
"(" printf("Open paren\n");
")" printf("Close paren\n");
{ID} printf("Identifier: %s\n",yytext);
"+"|"-"|"*"|"/" printf("Operator: %s\n",yytext);
">"|"<" printf("Relational operator: %s\n",yytext);
"{"[^}\n]*"}" /* skip one-line comments */
[ \t\n]+ /* skip whitespace */
. printf("UNRECOGNIZED: %s\n",yytext);
%%
main(){ yylex(); }
I tried ignoring the error, since lex.yy.c was still created, and entered "cc lex.yy.c -lfl", but I get the error:
Code:
/usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libfl.a(libmain.o): In function `main':
(.text+0x21): undefined reference to `yylex'
collect2: ld returned 1 exit status
If it helps, I'm accessing the linux account via ssh (copied the error message from the putty.log). I'm just entering these commands into the command line and editing the files with emacs. I have a very limited access to the system, and I don't know how to get rid of that error. I need to add those lines for the project.
Re: flex "flex scanner push-back overflow"
This is screwed up. I've narrowed the issue down to one line in new_scanner.l:
Code:
EXP {EXP}{SP}("+"|"-"|"*"|"/"){SP}{VAL}|{VAL}
I ruled it further down to the recursive definition! I don't understand, and I must less care. I rewrote it without the {EXP} and now it works!
Code:
BINOP "+"|"-"|"*"|"/"
EXP_END ({SP}{BINOP}{SP}{VAL})*
and I rewrote the conditional regex:
Code:
{VAL}{EXP_END}{SP}(">"|"<"){SP}{VAL}{EXP_END}
win.
