cin

I was trying to read from standard input. The first line is the number of lines that I will read. The lines that I read next will be printed again. Here is the code: #include <iostream> using namespace std; int main() { int n; cin >> n; for (unsigned int i = 0; i < n; ++i) { char a[10]; cin.get (a, 10); cout << "String: " << a << endl; } return 0; } When I run it and give number of lines, the program exits. I haven't figured out what's going on, so I've decided to ask it here. Thanks in advance. Mixing formatted and unformatted input is fraught with problems. In your particular case, this line

This question already has an answer here: Are there any tricks to use std::cin to initialize a const variable? 6 answers Can the following two lines be condensed into one? int foo; std::cin >> foo; The smart-ass answer: int old; std::cin >> old; The horrible answer: int old, dummy = (std::cin >> old, 0); The proper answer: old has to be defined with a declaration before it can be passed to operator>> as an argument. The only way to get a function call within the declaration of a variable is to place it in the initialization expression as above. The accepted way to declare a variable and read

I am new to C++ and I was wondering how the function cin in case of a boolean data works. Let's say for instance : bool a; cin >> a; I understand that if I give 0 or 1, my data a will be either true or false. But what happens if I give another integer or even a string ? I was working on the following code : #include <iostream> using namespace std; int main() { bool aSmile,bSmile; cout << "a smiling ?" << endl; cin >> aSmile; cout << "b smiling ?" << endl; cin >> bSmile; if (aSmile && bSmile == true) { cout << "problem"; } else cout << "no problem"; return 0; } If I give the values of 0 or 1

I was wondering how to use cin so that if the user does not enter in any value and just pushes ENTER that cin will recognize this as valid input. Martin Cote You will probably want to try std::getline : #include <iostream> #include <string> std::string line; std::getline( std::cin, line ); if( line.empty() ) ... I find that for user input std::getline works very well. You can use it to read a line and just discard what it reads. The problem with doing things like this, // Read a number: std::cout << "Enter a number:"; std::cin >> my_double; std::count << "Hit enter to continue:"; std::cin >>

For example, #include <iostream> int main() { unsigned n{}; std::cin >> n; std::cout << n << ' ' << (bool)std::cin << std::endl; } When input -1 , clang 6.0.0 outputs 0 0 while gcc 7.2.0 outputs 4294967295 1 . I'm wondering who is correct. Or maybe both are correct for the standard does not specify this? By fail, I take to mean (bool)std::cin be evaluated false. clang 6.0.0 fails input -0 too. As of Clang 9.0.0 and GCC 9.2.0, both compilers, using either libstdc++ or libc++ in the case of Clang, agree on the result of the program above, independent of the C++ version (>= C++11) used, and print

有时候时间久了，一些基本功就会忘了，这里记录一下。 问题： 在写CPP程序时，报错： 未声明的cin和cout 代码举例如下： #include "stdafx.h" using namespace std; #include <iostream> int main() { int flag = 0; if (flag) cout<<"success!"; else cout<<"error"; return 0； } 乍一看没问题啊！后来发现 using namespace std; 要紧跟在这句引用的后面 #include <iostream> 解决： 正确的顺序为 #include "stdafx.h" #include <iostream> using namespace std; 文章来源: C++杂记（一）――未声明的cin和cout（已声明std空间情况下）