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Old 04-06-2010, 06:12 AM   #1
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Registered: Apr 2010
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flex and bison

i have written two files which are given below.
extern int yylval;

[0-9]+ {yylval=atoi(yytext); return NUMBER;}
[ /t] ;
\n return 0;
. return yytext[0];




#include <stdio.h>


%left '+' '−'

%left '∗'

%token NUMBER


input :

| input expr '\n' { printf(”result=%d\n”,$2); }


expr : NUMBER

| expr '+' expr { $$ = $1 + $3;}

| expr '−' expr { $$ = $1 − $3;}

| expr '∗' expr { $$ = $1 ∗ $3;}



int main(){yyparse();}

this is what i am doing at terminal and errors are generated

root@sandy:/home/sandy/lexyacc# bison -d -y ex1.y
root@sandy:/home/sandy/lexyacc# flex ex2.l
root@sandy:/home/sandy/lexyacc# gcc -o calc lex.yy.c -lm -lfl
ex2.l:2:10: error: #include expects "FILENAME" or <FILENAME>
ex2.l: In function ‘yylex’:
ex2.l:5: error: ‘yylval’ undeclared (first use in this function)
ex2.l:5: error: (Each undeclared identifier is reported only once
ex2.l:5: error: for each function it appears in.)
ex2.l:5: error: ‘NUMBER’ undeclared (first use in this function)

So please help me out in solving these errors
Old 04-06-2010, 06:38 AM   #2
Registered: Jan 2010
Location: Lancashire
Distribution: Slackware Stable
Posts: 553

Rep: Reputation: 116Reputation: 116
First thing - running as root!?!?!?!?!

Second - do you need the -y flag passed to bison? Also there is no need for linking to the flex lib in your compilation as you have defined your own main() function.

This article may help you:


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