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apache-flexeof

Premature EOF error in flex

When I run the following code in flex , i get premature EOF at the last line as an error. If the definition part is removed no error is generated.Why is this so??

%{
     #include <stdio.h>
       int x = 0;
}%

%%
"a"  {x=x+1; printf("id %d",x); }
%%

int yywrap(void)
{
    return 0;
}

int main(void)
{
int x = 0;
    yylex();
    return 0;
}
Solution

  • The third line of your code has the problem . It should be %} instead of }%

    Try this :

    %{
x = 0;
%}

%%
[a]  {x++; printf("id %d",x); }
%%

int main(void)
{
    yylex();
    return 0;
}

    I don't know what you intend to do but a working example that will print an id for every a encountered in input file will somewhat look like this :

    %{
x = 0;
%}

%%
[a]  {x++; printf("id %d ",x); }
%%

int main(int argc,char * argv[])
{
  yyin = fopen(argv[1],"r");
  yylex();
  fclose(yyin);
  return 0;
}