reading from file

This is a discussion on reading from file within the C++ Programming forums, part of the General Programming Boards category; Having a problem reading from an input file. Have two sets of data- account numbers and balances. I set them ...

  1. #1
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    reading from file

    Having a problem reading from an input file. Have two sets of data- account numbers and balances. I set them up in parallel arrays but the book im using does not explain anything about reading from a file. Just curious how I could read the arrays from a function.

  2. #2
    & the hat of GPL slaying Thantos's Avatar
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  3. #3
    Registered User
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    Something is wrong with my functions but I havent been able to find a good resource to help me out. I am getting errors saying my customer and balance array are unrefereneced. Any help would be appreciated

    Code:
     
    #include <iostream>
    #include <fstream>
    #include <iomanip>
    #include <cmath>
    
    using namespace std;
    
    void headings(ofstream &outFile);
    void readData(ifstream &inFile);
    void sort(ifstream &inFile);
    
    int main()
    {
    	const int size = 50;
    	
    	//declare variables
    	int customer[size];
    	double balance[size];
    	
    	//open files
    	ifstream inFile;
    	ofstream outFile;
    	inFile.open("prog7.txt");
    	outFile.open("prog7.out");
    
    	headings(outFile);
    	
    	// read from file
    	double temp = 0;
    	readData(inFile);
    	while (!inFile.eof())
    {
    	readData(inFile);
    	temp ++;
    }
    	sort(inFile);
    	outFile.close();
    	inFile.close();
    	return 0;
    }
    	void headings(ofstream &outFile)
    	{
    		
    		outFile <<setw(10)<< "Customer ID"
    				<<setw(10)<< "Balance"
    				<<endl;
    	}
    	void readData(ifstream &inFile)
    		{
    			double temp = 0;
    			inFile >> customer[temp] >> balance[temp];
    		}
    	void sort(ifstream &inFile)
    		{
            	for(int j=1; j< size; j++)
    			{
    				for(int i=0; i< size-1; i++)
    				{
    					if(balance[i] > balance[i+1]
    					{
    						temp=balance[i];
    						balance[i]=balance[i+1];
    						balance[i+1]=temp;
    					}
    				}
    			}
    		}
    	void printResults(ofstream &outFile, ifstream &inFile)
    		{
    			outFile << setprecision(2) << fixed << showpoint;
    			outFile <<setw(10)<< customer[size]
    					<<setw(10)<< balance[size]
    					<<endl << endl;
    		}

  4. #4
    & the hat of GPL slaying Thantos's Avatar
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    You need to pass them to the functions. customer is declared in main so only main can see it.
    IE:
    Code:
    void readData(ifstream &inFile, int customer[], double balance[])
    {
    double temp = 0;
    inFile >> customer[temp] >> balance[temp];
    }
    which then would be called with:
    Code:
    readData(inFile, customer, balance);
    However that function has an error in that temp is a double but you are using it as the index to an array

  5. #5
    diligentStudent()
    Join Date
    Apr 2002
    Posts
    79
    Hi. I get a bunch of compile-time errors with your code. Be careful:
    Code:
        if(balance[i] > balance[i+1]
    You haven't closed the parenthesis of the if conditional.
    Correct:
    Code:
        if(balance[i] > balance[i+1])
        {
            /*...*/
        }
    Good Luck,
    Steve

  6. #6
    Registered User
    Join Date
    Dec 2004
    Posts
    10
    ok thanks for the help so far. I cleaned up the code and managed to get no errors after debugging, but still am not getting any output. Not sure how to add reference variables to arrays while in a function. Any help on how to do this or what my problem might be would be greatly appreciated.

    Code:
    #include <iostream>
    #include <fstream>
    #include <iomanip>
    #include <cmath>
    #define size 50
    
    using namespace std;
    
    void headings(ofstream &outFile);
    void readData(ifstream &inFile, int customer[], float balance[]);
    void sort(ifstream &inFile, float balance[]);
    void printResults(ofstream &outFile, ifstream &inFile, int customer[], float balance[]);
    
    int main()
    {
    	//declare variables
    	int customer[size];
    	float balance[size];
    	
    	//open files
    	ifstream inFile;
    	ofstream outFile;
    	inFile.open("prog7.txt");
    	outFile.open("prog7.out");
    
    	// funtion to print headings
    	headings(outFile);
    	
    	// read from file
    	float temp = 0;
    	readData(inFile, customer, balance);
    	
    	// loop
    	while (!inFile.eof())
    	{
    		readData(inFile, customer, balance);
    		temp ++;								
    	}
    	
    	// function to sort in descending order
    	sort(inFile, balance);
    
    	// function to print results
    	printResults(outFile, inFile, customer,  balance); 
    
    
    	outFile.close();
    	inFile.close();
    	return 0;
    }
    	void headings(ofstream &outFile)
    	{
    		outFile <<setw(10)<< "Customer ID"
    				<<setw(10)<< "Balance"
    				<<endl;
    	}
    	void readData(ifstream &inFile, int customer[], float balance[]) 
    		{
    			static int i = 0;			  
    			static int j = 0;
    			inFile >> customer[j] >> balance[i];
    		}
    	void sort(ifstream &inFile, float balance[])
    		{
    			float temp = 0;			
            	for(int j=1; j< size; j++)
    			{
    				for(int i=0; i< size-1; i++)
    				{
    					if(balance[i] > balance[i+1])
    					{
    						temp=balance[i];
    						balance[i]=balance[i+1];
    						balance[i+1]=temp;
    					}
    				}
    			}
    		}
    	void printResults(ofstream &outFile, ifstream &inFile, int customer[], float balance[])
    		{
    			outFile << setprecision(2) << fixed << showpoint;
    			outFile <<setw(10)<< customer
    					<<setw(10)<< balance
    					<<endl << endl;
    		}

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