从文件读取导致无限循环的问题 [英] Problem with reading from file causing infinite loop

问题描述

确定这个程序我正在工作似乎一切正常，除了有一个问题。这是代码

Ok this program I am working on seems to be all ok except there is a problem. Here is the code

#include <iostream>
#include <fstream>

using namespace std;

/*
Function Name: CalculateBinary
CalculateBinary takes a number from the main function and finds its binary form.
*/

void CalculateBinary( long InputNum)
{   
    //Takes InputNum and divides it down to "1" or "0" so that it can be put in binary form.
    if ( InputNum != 1 && InputNum != 0)
        CalculateBinary(InputNum/2);

    // If the number has no remainder it outputs a "0". Otherwise it outputs a "1". 
    if (InputNum % 2 == 0)
        cout << "0";
    else
        cout << "1";
}


void main()
{
    // Where the current number will be stored
      long InputNum;

    //Opens the text file and inputs first number into InputNum. 
    ifstream fin("binin.txt");
    fin >> InputNum;

    // While Input number is not 0 the loop will continue to evaluate, getting a new number each time.
    while (InputNum >= 0)
    {
        if(InputNum > 1000000000)
            cout << "Number too large for this program ....";
        else
            CalculateBinary(InputNum);

        cout << endl;
        fin >> InputNum;        
    }
}

这是我正在阅读的文本文件

Here is the text file I am reading in

12
8764
 2147483648
2
-1

当我到达8764，它只是继续读这个数字一遍又一遍。它忽略了2147483648.我知道我可以通过声明InputNum为long long解决这个问题。但是我想知道为什么要这样做。

When I get to 8764, it just keeps reading in this number over and over again. It ignores the 2147483648. I know I can solve this by declaring InputNum as a long long. But I want to know why is it doing this?

推荐答案

这是你写的循环的常见问题。

That is the usual problem with such loops which you've written.

正确的和惯用的循环是：

The correct and the idiomatic loop is this:

ifstream fin("binin.txt");
long InputNum;
while (fin >> InputNum && InputNum >= 0)
{
   //now construct the logic accordingly!
    if(InputNum > 1000000000)
         cout << "Number too large for this program ....";
    else
         CalculateBinary(InputNum);
    cout << endl;
}

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