reading into code from .txt [c++]

Question

I am trying to code up an adventure game that reads from a script on a text file. The program compiles and runs but it does not read from my .txt file and I cannot figure out what is going wrong.

In my GetAreaInfo function the line

"fin.seekg(NULL,ios::beg);" shows a warning saying

"main.cpp:92:28: warning: passing NULL to non-pointer argument 1 of 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::seekg(std::basic_istream<_CharT, _Traits>::off_type, std::ios_base::seekdir) [with _CharT = char; _Traits = std::char_traits; std::basic_istream<_CharT, _Traits>::off_type = long int; std::ios_base::seekdir = std::_Ios_Seekdir]' [-Wconversion-null]"

I cannot figure out how to make this go away but I beleive it is the problem. Any help would be much appreciated

[code]

//file libraries
#include <iostream>
#include <fstream>
#include <string>
#include <windows.h>
using namespace std;

#define GAMEFILE "world.txt"//read in for the world data
#define CONTINUE    1
#define QUIT            0

//user libraries
struct tArea{//structure that holds the info for the main area

    string strCurrentArea;//name of current area
    string strDescription;//description of current area
    string strNorth;//name of area to the north
    string strSouth;//name of area to the south
    string strEast;//name of area to the east
    string strWest;//name of area to the west

};
//global constants

//function prototypes
void DisplayArea(tArea &area);
void GetAreaInfo(ifstream&,tArea &area);
void Move(ifstream&,tArea &area,string);
int Input(ifstream&,tArea &area);
//execution
int main(){

    ifstream fin;//pointer that opens and reads from file
    tArea area;//area structure data

    fin.open(GAMEFILE);//

    if(fin.fail()){
        cout<<"UNABLE TO FIND GAME FILE\n";

        return -1;
    }
    fin>>area.strCurrentArea>>area.strCurrentArea;//reads in the start point for the game

    GetAreaInfo(fin,area);//calls function to receive info from the file

    DisplayArea(area);//calls function to display the area to the user

    while(1){//main game loop


        if(Input(fin,area)==QUIT){//if user enters quit, game ends

            break;
        }
    }

    fin.close();//closes file

    Sleep(1000);//1 second delay before ending

    return 0;
}
/**********************************************************/
//*****************DisplayArea*****************************/
//******Function is called to display area description*****/
/**********************************************************/
void DisplayArea(tArea &area)
{

    cout<<area.strDescription<<endl<<endl;      
}
/**********************************************************/
//*****************GetAreaInfo*****************************/
//******Function is called to read in the area*************/
//************information from the file********************/
/**********************************************************/
void GetAreaInfo(ifstream &fin,tArea &area){

    string strTemp="";
    string strTemp2="";//temporary for reading in info

    string strArea="<"+area.strCurrentArea+">";//looks for the room name in brackets to find easier i.e instead of main it reads in <main>

    fin.seekg(NULL,ios::beg);//starts the header search from the beginning of the file

    fin.clear();//allows the file to be read through multiple times

    while(getline(fin, strTemp, '\n')){//while loop reads file til it finds the correct area heading

        if(strTemp==strArea){

            getline(fin, area.strDescription, '*');//if it finds the correct area heading, it reads its info    

            // Read past the direction blocks (I.E. <north>) and store the room name for that direction
            fin>>strTemp>>area.strNorth;                
            fin>>strTemp>>area.strEast;             
            fin>>strTemp>>area.strSouth;                
            fin>>strTemp>>area.strWest;//it then read in the surrounding area titles by skipping their <area> descriptors               


            return;                                 
        }
    }
}
/**********************************************************/
//*********************Move********************************/
//******Function is called to move through the*************/
//****game if there is an area in that direction***********/
/**********************************************************/
void Move(ifstream &fin,tArea &area, string strArea){

    if(strArea=="None"){//detects if there is no area in the direction inputted             

        cout<<"You are unable to travel that way\n";//displays error message and returns the function
        return;                                 
    }
    else{

        area.strCurrentArea=strArea;// Sets the current area to the new one

    GetAreaInfo(fin, area); // Passes in the file pointer so the new area data is read  

    DisplayArea(area);// Displays current area

    }
}
/**********************************************************/
//*********************Input*******************************/
//******Main game mechanic feature. Receives **************/
//****user input and reacts to it accordingly to **********/
//*******progress through the game*************************/
/**********************************************************/
int Input(ifstream &fin, tArea &area){

    string strInput="";//holds user input

    cout<<endl<<":";//displays prompt
    cin>>strInput;//reads in the user input

    if(strInput=="look"){
        DisplayArea(area);//calls function to give current area description
    }
    else if(strInput=="north"){
        Move(fin,area,area.strNorth);//calls function to move north if possible
    }
    else if(strInput=="east"){
        Move(fin,area,area.strEast);//calls function to move east if possible
    }
    else if(strInput=="west"){
        Move(fin,area,area.strWest);//calls function to move west is possible
    }
    else if(strInput=="south"){//calls function to move south if possible
        Move(fin,area,area.strSouth);
    }
    else if(strInput=="help"||strInput=="?"){//displays commands to user
        cout<<"Commands: north east west south look quit help\n";
    }
    else if(strInput=="quit"){//ends game
        cout<<"Quit game?\n";
        return QUIT;
    }
    else{//displays when invalid input is received
        cout<<"Invalid input\n";
    }

    return CONTINUE;
}

Answer 1

iostream::seekg has the following signature:

1. istream& seekg (streampos pos);
2. istream& seekg (streamoff off, ios_base::seekdir way);

NULL on the other hand is a null pointer constant.

You probably mean to write:

fin.seekg(0, ios::beg);

or simply:

fin.seekg(0);

Both of these will start seeking from the beginning.