I'm encountering issues with my Flex and Bison integration, specifically related to errors like "stray ` in program"and"expected ';' before '{' token." I've checked my code, but I'm unable to pinpoint the exact problem.
The errors:
lab4.l: In function 'yylex':
lab4.l:10:18: error: expected ';' before '{' token
"#include" { return INCLUDE; }
^
lab4.l:29:13: error: stray '\' in program
[-]?[0-9]+(\.[0-9]+)? { return CONST; }
^
lab4.l:52:3: error: stray '\' in program
[\n] { line++; }
^
The lex code:
%{
#include "lab4.tab.h"
int line = 1;
%}
%option noyywrap
%%
"#include" { return INCLUDE; }
"cin" { return CIN; }
"cout" { return COUT; }
"main()" { return MAIN; }
"namespace" { return NAMESPACE; }
"std" { return STD; }
"int" { return INT; }
"void" { return VOID; }
"double" { return DOUBLE; }
"<iostream>" { return IOSTREAM; }
"<fstream>" { return IOSTREAM; }
"using" { return USING; }
"if" { return IF; }
"else" { return ELSE; }
"while" { return WHILE; }
"struct" { return STRUCT; }
[1-9]* { return DIGIT; }
[a-zA-Z][1-9]* {0, 250} { return ID; }
[-]?[0-9]+(\.[0-9]+)? { return CONST; }
[1-9]* { return NZD; }
[a-zA-Z]* { return CHAR }
"{" { return LBR; }
"}" { return RBR; }
"(" { return LPR; }
")" { return RPR; }
">>" { return RS; }
"<<" { return LS; }
"<" { return LT; }
">" { return GT; }
">=" { return GTE; }
"<=" { return LTE; }
"+" { return PLUS; }
"-" { return MINUS; }
"*" { return MUL; }
"/" { return DIV; }
";" { return SEMICOLON; }
"=" { return ASSIGN; }
"!=" { return DIFF; }
"." { return DOT; }
[\n] { line++; }
%%
The bison code:
%{
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern int yylex();
extern int yyparse();
extern FILE* yyin;
extern int line;
void yyerror();
%}
%token DIGIT CONST ID CHAR NZD
%token INCLUDE USING NAMESPACE STD IOSTREAM FSTREAM
%token INT MAIN DOUBLE VOID STRUCT
%token LPR RPR LBR RBR
%token CIN COUT
%token IF WHILE SEMICOLON DOT
%left ELSE
%left ASSIGN DIFF LS RS
%left LT GT LTE GTE
%left PLUS MINUS MUL DIV
%%
program : headers_block main_block
;
headers_block : headers_list USING NAMESPACE STD SEMICOLON
;
headers_list : header headers_list
| header
header : INCLUDE library
;
library : IOSTREAM
| FSTREAM
;
main_block : type MAIN LBR instr_list RBR
;
type : VOID
| INT
| DOUBLE
| triple
| point
;
triple : NZD DOT DIGIT DIGIT DIGIT
;
point : STRUCT LBR INT ID SEMICOLON INT ID SEMICOLON RBR ID SEMICOLON
;
instr_list : instr instr_list
| instr
;
instr : atribuire
| read
| write
| if_instr
| while_instr
;
atribuire : type ID SEMICOLON
| ID ASSIGN expr SEMICOLON
;
expr : ID
| CONST
| operand expr
;
operand : ID
| CONST
| CONST operator ID
| id_expr
;
id_expr : ID operator ID
;
operator : PLUS
| MINUS
| DIV
| MUL
| LT
| GT
| DIFF
| LTE
| GTE
| ASSIGN
| RS
| LS
;
read : CIN RS ID SEMICOLON
;
write : COUT LS ID SEMICOLON
;
if_instr : IF LPR expr RPR LBR atribuire RBR else_instr
| IF LPR expr RPR LBR atribuire RBR
;
else_instr : ELSE LBR atribuire RBR
;
while_instr : WHILE LPR expr RPR LBR instr RBR
;
%%
int main(int argc, char* argv[]){
++argv, --argc;
if(argc > 0){
yyin = fopen(argv[0], "r");
} else {
yyin = stdin;
}
while(!feof(yyin)){
yyparse();
}
printf("Result: OK\n");
return 0;
}
void yyerror(){
printf("Error at line %d!\n", line);
exit(1);
}
How can I resolve these errors in the context of Flex and Bison interaction? I've included relevant sections of my code above for reference.
You have several issues with your Flex input, among them:
Flex is sensitive to indentation. The pattern in each rule must not be indented. It must start at the beginning of its line.
You are missing a semicolon in the action for this rule:
[a-zA-Z]* { return CHAR }
You have two different rules with pattern [1-9]*, returning different token types.
Patterns must not contain unquoted whitespace characters, such as in this rule:
[a-zA-Z][1-9]* {0, 250} { return ID; }
Remove the spaces in the pattern.