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这是参考我问的另一个问题,尽管这完全是它自己的问题。

编译时出现两个错误:

1>.\asst4.cpp(73):错误 C2065:'outfile':未声明的标识符

1>.\asst4.cpp(73) : 错误 C2228: '.close' 左侧必须有类/结构/联合

我对我在这里做错了什么感到有些困惑?有什么建议或想法吗?(实际的输出文件靠近代码的顶部。

这是完整的代码:

#include<iostream>
#include<fstream>  //used for reading/writing to files.
#include<string>    //needed for the filename.
#include<stdio.h>   //for goto statement

using namespace std;

int main()
{
    string start;
    char choice;
    char letter;
    int x;
    int y;
    int z;
    string filename;
    int garbage = rand()%('!' - '~' + 1 );
    cout << "Would you like to encrypt or decrypt a file? Please type enc, dec, or stop (case sensitive): " ;
    cin >> start;
    while(start == "enc")
    {
        x = 1;
        y = 1;
        cout << "How many garbage characters would you like between each correct character?: " ;
        cin >> z;
        cout << endl << "Please insert the name of the document you wish to encrypt, make sure you enter the name, and the file type (ie: filename.txt): " ;
        cin >> filename;
        ifstream infile(filename.c_str());
        while(!infile.eof())
        {
            ofstream outfile("encrypted.txt", ios::out);
            infile.get(letter); 
            if (x == y)         
                {
                outfile << garbage;
                x++;             
            }
            else
            {
                if((x - y) == z)            
                {
                    outfile << letter;          
                    y = x;                  
                }
                else                        
                {                           
                    outfile << garbage;
                    x++;
                }
            }
        }
        cout << endl << "Encryption complete...please return to directory of program, a new file named encrypted.txt will be there." << endl;
        infile.close();
        outfile.close();
        cout << "Do you wish to try again? Please press y then enter if yes (case sensitive).";
        cin >> choice;
        if(choice == 'y')
        {
            start = "enc";
        }
        else
        {
            cout << endl << "Do you wish to decrypt a file? Please press y then enter if yes (case sensitive).";
            if(choice = 'y')
            {
                start == "dec";
            }
            else
            {
                start == "no";
            }
        }
    }
    while(start == "dec")
    {

      //lets user choose whether to do another document or not.
      //used to track each character in the document.
        x = 1;    //first counter for tracking correct letter.
        y = 1;    //second counter (1 is used instead of 0 for ease of reading, 1 being the "first character").
              //third counter (used as a check to see if the first two counters are equal).
        //allows for user to input the filename they wish to use.
        cout << "Please make sure the document is in the same file as the program, thank you!" << endl << "Please input document name: " ;
        cin >> filename; //getline(cin, filename);  
        cout << endl;
        cout << "'Every nth character is good', what number is n?: ";
        cin >> z;   //user inputs the number at which the character is good. IE: every 5th character is good, they would input 5.
        cout << endl;
        z = z - 1;  //by subtracting 1, you now have the number of characters you will be skipping, the one after those is the letter you want.
        ifstream infile(filename.c_str()); //gets the filename provided, see below for incorrect input.
        if(infile.is_open()) //checks to see if the file is opened.
        {
            while(!infile.eof())    //continues looping until the end of the file.
            {   
                    infile.get(letter);  //gets the letters in the order that that they are in the file.
                    if (x == y)          //checks to see if the counters match...
                    {
                        x++;             //...if they do, adds 1 to the x counter.
                    }
                    else
                    {
                        if((x - y) == z)            //for every nth character that is good, x - y = nth - 1.
                        {
                            cout << letter;         //...if they don't, that means that character is one you want, so it prints that character.
                            y = x;                  //sets both counters equal to restart the process of counting.
                        }
                        else                        //only used when more than every other letter is garbage, continues adding 1 to the first
                        {                           //counter until the first and second counters are equal.
                            x++;
                        }
                    }
            }
            cout << endl << "Decryption complete...please return to directory of program, a new file named encrypted.txt will be there." << endl;
            infile.close();
            cout << "Do you wish to try again? Please press y then enter if yes (case sensitive).";
            cin >> choice;
            if(choice == 'y')
            {
                start == "dec";
            }
            else
                {
                cout << endl << "Do you wish to encrypt a file? Please press y then enter if yes (case sensitive).";
                if(choice == 'y')
                {
                    start == "enc";
                }
                else
                {
                    start == "no";
                }
            }
        }
        else  //this prints out and program is skipped in case an incorrect file name is used.
        {
            cout << "Unable to open file, please make sure the filename is correct and that you typed in the extension" << endl;
            cout << "IE:" << "     filename.txt" << endl;
            cout << "You input: " << filename << endl;
            cout << "Do you wish to try again? Please press y then enter if yes (case senstive)." ;
            cin >> choice;
            if(choice == 'y')
            {
                start == "dec";
            }
            else
            {
                start == "no";
            }
        }
        getchar();  //because I use visual C++ express.
    }
}

提前谢谢!杰夫

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2 回答 2

2

范围问题。您在 while 循环中声明 outfile ,但试图在所述 while 循环之外访问它。

移动ofstream outfile("encrypted.txt", ios::out);到你之后的那一行ifstream infile(filename.c_str());是你之前的while(!infile.eof())

于 2009-03-07T10:58:42.157 回答
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You've got two choices - as X-istence mentions, the reason your call to outfile.close() is not compiled is because the object 'outfile' does not exist in the same scope as the declaration of outfile.

You could either move the line


ofstream outfile("encrypted.txt", ios::out);

outside the while loop so it obeys the same scoping rules as infile, or you can move your call to outfile.close(); inside the while loop, which would move it into the current scope in which outfile exists.

My preference would be to move the declaration of outfile outside the while loop as opening a file is quite an expensive operation and you really don't want to do this for every letter you read from infile. Open it once, close it once is the way to go in this case.

于 2009-03-07T11:13:05.057 回答