String Library Usage in Yacc File

Question

I am trying to write a compiler using lax and yacc. I started by defining the tokens and syntax tree with adding any associated actions, but when I compile it, I get some errors.

Lexer:

%{
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "y.tab.h"
%}

%%

" " {};
"is" {};
[A-Z]+ { return LAYER;}
[0-9]+\.*[0*9]* {return NUMBER;}
"minimum width" {return MIN_WIDTH;}
"maximum width" {return MAX_WIDTH;}
"minimum length" {return MIN_LENGTH;}
"maximum length" {return MAX_LENGTH;}
"minimum space to" {return MIN_SPACE_TO;}
"minimum space" {return MIN_SPACE;}
"with minimum width" {return MIN_W_FILTER;}
"with minimum span" {return MIN_SPAN_FILTER;}

%%

Parser:

%{
#include <stdio.h>
#include <string.h>

extern FILE * file_in;
%}

%start rule

%token <strval> LAYER NUMBER MIN_WIDTH MAX_WIDTH MIN_LENGTH MAX_LENGTH MIN_SPACE MIN_SPACE_TO MIN_W_FILTER MIN_SPAN_FILTER
%%

rule:
    LAYER operation NUMBER {}
    |
    derived_layer operation NUMBER {}
    ;


derived_layer:
    '(' LAYER filter NUMBER ')' {}
    |
    '(' LAYER operation LAYER ')' {}
    ;

operation:
    MIN_WIDTH {}
    |
    MAX_WIDTH {}
    |
    MIN_LENGTH {}
    |
    MAX_LENGTH {}
    |
    MIN_SPACE_TO {}
    ;

filter:
    MIN_W_FILTER {}
    |
    MIN_SPAN_FILTER {}
    ;

%%

int parsefile (const char * FileName)
{

   FILE * fileIn;
   string strFileName = string(FileName);
   fileIn = fopen(strFileName.c_str(),"r");
   if(!fileIn)
   {
      Std::cout << “error while opening file\n”;
   }
   else
   {
      file_in = fileIn;
      flag = cdfparse();

      if(fileIn)
      {
         fclose(fileIn);
      }
   }
}

I get the following errors:

drc.y: In function ‘parsefile’:
drc.y:53: error: ‘string’ undeclared (first use in this function)
drc.y:53: error: (Each undeclared identifier is reported only once
drc.y:53: error: for each function it appears in.)
drc.y:53: error: expected ‘;’ before ‘strFileName’
drc.y:54: error: ‘strFileName’ undeclared (first use in this function)
drc.y:57: error: expected expression before ‘:’ token
drc.y:57: error: stray ‘\342’ in program
drc.y:57: error: stray ‘\200’ in program
drc.y:57: error: stray ‘\234’ in program
drc.y:57: error: stray ‘\’ in program
drc.y:57: error: stray ‘\342’ in program
drc.y:57: error: stray ‘\200’ in program
drc.y:57: error: stray ‘\235’ in program
drc.y:62: error: ‘flag’ undeclared (first use in this function

I think the error means that the string library is not defined, but I've already included string.h in the header. Isn't that enough?

Answer 1

You need to include:

#include <string>
#include <iostream>

parsefile should return something or it should be void.

This statement:

string strFileName = string(FileName);

should be:

std::string strFileName = FileName;

this statement:

      Std::cout << “error while opening file\n”;

should be (notice the S in std and the quotes):

      std::cout << "error while opening file\n";

There is no definition or declaration of flag = cdfparse();, check it.

Answer 2

string.h contains string functions for char arrays. The string type is contained in the string file. Use #include <string>