Do-while不断循环cout,忽略cin [英] Do-while endlessly looping cout, ignores cin
问题描述
此程序在指定范围内打印指定数量的数字。然而,当我输入一个字符,它只是无休止地循环,无论do-while循环我在做什么。例如:如果我在输入最大数cin输入一个字符,它只是垃圾邮件输入最大数无休止,它只是跳过任何人都知道为什么?
#include< iostream> ;
#include< cmath>
#include< cstdlib>
#include< ctime>
使用命名空间std;
$ b b int roll(int mini,int maxi)
{
int v = maxi - mini;
int x = mini +(rand()%(v + 1));
return x;
}
void caller()
{
int a;
int b;
int c;
do {
cout<<Enter minimum number<< endl;
cin.clear();
cin>> a;
} while(cin.fail());
do {
cout<<<Enter maximum number<< endl;
cin.clear );
cin>> b;
} while(cin.fail()|| a> b);
do {
cout<< 多少卷? << endl;
cin.clear();
cin>> C;
} while(cin.fail());
for(int i = 0; i cout<辊(a,b) endl;
}
int main()
{
srand(time(NULL));
caller();
return 0;
}
code> istream :: fail()用于循环控制。请参阅为什么iostream :: eof处于循环条件中会被视为错误?类似的问题。
相反,我依赖 istream :: operator>>
的返回值。
我还使用以下函数重置标志并清除输入流上的输入:
void flush_stream :: istream& stream)
{
stream.clear();
stream.ignore(std :: numeric_limits< std :: riversize> :: max(),'\\\
');
}
查看如何刷新cin缓冲区?更多信息。
我会编写你的输入检查,因此:
int get_valid_number(const std :: string& prompt)
{
int number = 0;
bool valid = false;
while(!valid)
{
std :: cout<提示<< std :: endl;
if(std :: cin>> number)
{
valid = true;
}
flush_stream(std :: cin);
}
return number;希望将此提取到函数中的好处是显而易见的。 查看。
This program prints a specified amount of numbers within a specified range. However, when I enter a character, it just endlessly loops whichever do-while loop I do it in. E.g: If I enter a character in "Enter maximum number" cin, it just spams "Enter maximum number" endlessly, it just skips the cin and loops the cout (same goes for the other 2 do-whiles. Anyone know why?
#include <iostream>
#include <cmath>
#include <cstdlib>
#include <ctime>
using namespace std;
int roll(int mini, int maxi)
{
int v = maxi - mini;
int x = mini + (rand() % (v+1));
return x;
}
void caller()
{
int a;
int b;
int c;
do {
cout << "Enter minimum number" << endl;
cin.clear();
cin >> a;
} while (cin.fail());
do {
cout << "Enter maximum number" << endl;
cin.clear();
cin >> b;
} while (cin.fail() || a > b);
do {
cout << "How many rolls?" << endl;
cin.clear();
cin >> c;
} while (cin.fail());
for (int i = 0; i < c; i++)
cout << roll(a, b) << endl;
}
int main()
{
srand (time(NULL));
caller();
return 0;
}
解决方案 I prefer not to use istream::fail()
for loop control. See Why is iostream::eof inside a loop condition considered wrong? for a similar issue.
Instead, I rely upon the return value of istream::operator >>
.
I also use the following function to reset the flags and clear the input on input stream:
void flush_stream(std::istream& stream)
{
stream.clear();
stream.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}
See How do I flush the cin buffer? for more on this.
So I'd code your input checks thus:
int get_valid_number(const std::string& prompt)
{
int number = 0;
bool valid = false;
while (!valid)
{
std::cout << prompt << std::endl;
if (std::cin >> number)
{
valid = true;
}
flush_stream(std::cin);
}
return number;
}
Hopefully the benefits of extracting this into a function are obvious. See it run.
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