C ++ fstream讀寫文件

Question

我完全被困住了。 這是我不完整的程序。 程序卡在.at或確定元音行是否固定。 我需要一些建議來修復程序。 該程序應該執行的操作將使用包含以下行的文本文件：

C++ Programming is fun
Winter is here, will it ever end?
The style requirements document is so useful
Functions really make programming easier
Spring must be coming soon...
I wish this #$##$$!!## program was done
What comes after C++, D--?

我應該進行一些計算並導出到文件，因此它看起來像在此鏈接中： http : //tinypic.com/r/24fhbfb/5

到目前為止，這是我的代碼。 任何關於我在做什么錯的指針將不勝感激。 我必須在函數中做所有事情。

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>

using namespace std;

void OpenFiles (ifstream& inFile, ofstream& outFile);

void OutputDivider (ofstream& outFile, char symbol, int num);

void SetFileMessage (ifstream& inFile, bool& fileFound, string& message); 

void OutputFileMessage (bool& fileFound, ofstream& outFile, string& message);

void InitializeFileCounters (int& lineCounter, int& totalOfAs, int& characterTotal);

void OutputHeading (ofstream& outFile, string information, string name, int width);

string ReadALine (ifstream& inFile, int& lineLength);

void InitializeLineCounters (int& vowelCounter, int& charactersOfA, int& blankCounter);

void CalculateLineStats (ifstream& inFile, string readLine, int& vowelCounter, int&   lineLength,
                        int& blankCounter, int&  charactersOfA);



//Header to display in output file
const string INFORMATION = "CST 133 - Exercise 4";
const string MY_NAME = "Tom Hangler";

//Width of screen for dividers
const int SCREEN_WIDTH = 110;

int main(void)
{
    ifstream fin;
    ofstream fout;

    bool fileFound;

    string message;
    string lineCopy;

    int lineCounter;
    int totalOfAs;
    int characterTotal;
    int vowelCounter;
    int charactersOfA;
    int blankCounter;
    int lineLength;

    //Open input and output text files
    OpenFiles(fin, fout);

    //Set message based on if file was found or not
    SetFileMessage(fin, fileFound, message);

    //Output message to text file if file was not found
    OutputFileMessage(fileFound, fout, message);

    if (fileFound)
    {
        InitializeFileCounters(lineCounter, totalOfAs, characterTotal);

        OutputHeading(fout, INFORMATION, MY_NAME, SCREEN_WIDTH);

        InitializeLineCounters(vowelCounter, charactersOfA, blankCounter);

       ReadALine(fin, lineLength);

        CalculateLineStats(fin, lineCopy, vowelCounter, lineLength, blankCounter, charactersOfA);

        ReadALine(fin, lineLength);

    }   

    return 0;
}

void OpenFiles (ifstream& inFile, ofstream& outFile)
{
    inFile.open("LinesEx4.txt");
    outFile.open("Ex4Out.txt");
}

 void OutputDivider (ofstream& outFile, char symbol, int num)
{ 
    //Ouput to text file a divider with symbol '-' and specified length in 'num'
    outFile << setfill(symbol) << setw(num) << symbol << endl;
}

void SetFileMessage (ifstream& inFile, bool& fileFound, string& message)
{
    if (!inFile)
    {
        //Set message string to file not found.
        message = "Input file was not found.";

        //Set the file found flag 
        fileFound = false;
    }
    else
    {
        //Set the file found flag
        fileFound = true;

        //Set message string to file not found.
        message = "Processing continues, file successfully opened.";
    }
}

void OutputFileMessage (bool& fileFound, ofstream& outFile, string& message)
{
    if (fileFound == false)
    {
        //Output divider to text file
        OutputDivider(outFile, '-', SCREEN_WIDTH);

        //Output message to text file.
        outFile << message << endl;

        //Output divider to text file
        OutputDivider(outFile, '-', SCREEN_WIDTH);
    }
    else 
    {
        //Output divider to text file
        OutputDivider(outFile, '-', SCREEN_WIDTH);

        //Output message to text file.
        outFile << message << endl;

        //Output divider to text file
        OutputDivider(outFile, '-', SCREEN_WIDTH);
    }
 }

void InitializeFileCounters (int& lineCounter, int& totalOfAs, int& characterTotal)
{
    //Initialize variables for total counting
    lineCounter = 0;
    totalOfAs = 0;
    characterTotal = 0;
}

void OutputHeading (ofstream& outFile, string information, string name, int width)
{
    outFile << '\n' << endl;

    OutputDivider(outFile, '*', width);

    outFile << setfill(' ') << setw((width + information.length()) / 2) << information << endl;

    outFile << setfill(' ') << setw((width + name.length()) / 2) << name << endl;

     outFile << "Line" << setw(50) << "Length" << setw(15) << "# of Vowels" << 
    setw(15) << "# of As" << setw(15) << "# of Blanks" << endl;

     OutputDivider(outFile, '*', width);
  }

 string ReadALine (ifstream& inFile, int& lineLength)
{
     string readLine;

    getline(inFile, readLine);
    lineLength = readLine.length();

    return readLine;
}

void InitializeLineCounters (int& vowelCounter, int& charactersOfA, int& blankCounter)
 {
     //Initialize variables for line analysis
     vowelCounter = 0;
    charactersOfA = 0;
    blankCounter = 0;
}

void CalculateLineStats (ifstream& inFile, string readLine, int& vowelCounter, int&    lineLength,
                                int& blankCounter, int&  charactersOfA)
{
    int index;

     for (index = 0; index < lineLength; index++)
   {
        if (readLine.at(index) == 'A' || readLine.at(index) == 'E' || readLine.at(index) == 'I'
                    || readLine.at(index) == 'O' || readLine.at(index) == 'U')
        {
            vowelCounter++;
        }
        if (readLine.at(index) == ' ')
        {
             blankCounter++;
        } 
        if (readLine.at(index) == 'A') 
        {
            charactersOfA++;
         }
    }  

}

Answer 1

您不是從ReadALine()存儲返回值，而是將lineLength > 0傳遞給CalculateLineStats() 。 這將導致at()拋出std::out_of_range異常，該異常不會被調用方捕獲，並會導致程序異常終止。

改成：

lineCopy = ReadALine(fin, lineLength);

沒有理由將lineLength存儲在單獨的變量中。

Answer 2

好像您將空字符串lineCopy傳遞給函數CalculateLineStats作為第二個參數，然后調用.at() 。 在調用此函數之前，應先將其讀入其中。