cout | 易学教程

Why cout is producing no output on Code Blocks?

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问题 #include <iostream> using namespace std; int main(int argc, char** argv) { cout << "Whatever"; return 0; } Cout does not work, nor printf, nor puts, nor anything. Also, I've checked the project properties and both the debug and release are set to "Console Application" and to "Pause in the end". It makes no sense. Edit: Also, I've tried to flush with endl before (No results). 回答1: I am writing my comment as a response: Your image shows option "-mwindows", that removes the console, as said at

How to Align text to the right using cout?

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问题 Suppose I have a string s which is given below: string s="i am\ngoing\nto\ncuet"; I want to align the string to the right during display in console. So I want to show output like this: EDIT: rightmost characters should be aligned. i am going to cuet I tried this code to show the output: cout.width(75); cout<<s; But it only right align the first line like this: i am going to cuet Then I tried this code to get the output: for(int i=0 ; i<s.size(); i++) { cout.width(75); cout<<s[i]; } But I get

C++ ofstream vs. C++ cout piped to file

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问题 I'm writing a set of unit tests that write calculated values out to files. Each test produces a square matrix that holds anywhere from 50,000 to 500,000 doubles, and I have a total of 128 combinations of test cases. Is there any significant overhead involved in writing cout statements and then piping that output to files, or would I be better off writing directly to the file using an ofstream? 回答1: This is going to be dependent on your system and environment. This likely to be very little

C++输出cout格式控制与定制

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输出格式制输出 cout是STL库中的iostream实例，用于格式化输出。输出格式化格式相关操作需包含<iomanip>，标志位等定义在<ios>或<iostream>中。控制函数格式控制的成员一般有对应的控制符（在cout输出中使用）。 precision(n)：对应setprecision(n)，设置实数的精度； width(n)：对应setw(n)，设置字段宽度为n位； fill(c)：对应setfill(c)，设置填充字符为c； setf(f)：对应setiosflags(f)，设置输出格式状态； unsetf(f)：对应resetioflags(f)，删除格式状态；如，以下两种方式是等价的： for(int i=0; i<10; ++i){ cout<<setw(2)<<n+1<<endl; } for(int i=0; i<10; ++i){ cout.width(2); cout<<n+1<<endl; } 格式标志 cout维护一个当前的格式状态，setf/unsetf在当前状态基础上追加或移除指定格式，而flags则是直接指定格式（替换掉当前格式）。每种格式独占一位，可用或操作组合。 ios::dec 以10进制表示整数 ios::hex 以16进制表示整数 ios::oct 以8进制表示整数 ios::showbase 强制输出整数基数前缀

Displaying chars as ints without explicit cast

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问题 Every time I send a char to the cout object, it displays in ASCII characters unless I cast it to an int. Q: Is there a way to display the numerical value of a char without an explicit cast? I read somewhere that doing too many casts in your code could lead to a loss of integrity (of your program). I am guessing that chars display in ASCII for a particular reason, but I'm not sure why. I am essentially creating a game. I am using small numbers (unsigned chars) that I plan to display to the

Overload << operator to change “ ” to “\n”

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问题 I am trying to overload << operator. For instance cout << a << " " << b << " "; // I am not allowed to change this line is given I have to print it in format <literal_valueof_a><"\n> <literal_valueof_b><"\n"> <"\n"> I tried to overload << operator giving string as argument but it is not working. So I guess literal " " is not a string. If it is not then what is it. And how to overload it? Kindly help; Full code //Begin Program // Begin -> Non - Editable #include <iostream> #include <string>

Is cout Guaranteed to Have the ctype<char> facet?

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问题 Given: auto foo = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"s I can convert all the characters to lowercase by: use_facet<ctype<char>>(cout.getloc()).tolower(data(foo), next(data(foo), foo.size())); Live Example But this depends upon cout.getloc() containing the ctype<char> facet . Presuming that I'm using an unmodified cout can I assume that cout.getloc() will contain the facet ctype<char> or do I need to confirm this before use with: has_facet<ctype<char>>(cout.getloc()) 回答1: From cppreference: Each

C++ cout list with decimals aligned using setw(x) not put_money

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问题 C++ Code runs well, but currently outputting values to right but justified left and not lining up on the decimal. Can't use put_money, what am I missing? Attempted using fprint and put_money, confirmed with classmate we're supposed to use setw(x). #include <iostream> #include <string> #include <iomanip> using namespace std; int main() { const double taxRate = 0.09; const double laborCPH = 35.0; //where CPH is Cost Per Hour double costParts; double costLabor; double totalTax; double totalDue;

String is not printing without new line character in C++

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问题 I'm opening a file, and getting lines from it. The first line should say how many variables there are, and what their names are. The second line should be a logic equation using these variables. The assignment is to have it print out a truth table for the variables and equation. The first line the program is taking in is not printing without me inserting a new line character. I tried converting to a string and using both printf and cout. Main file that inputs everything: #include "truthTable2

Visual C++ 2012 cout crashes during run time

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问题 I decided to try Visual Studio 2012 Express today. First thing to do was to write "Hello world!" application, however, I couldn't make it work. I created a Windows console application project, wrote standard code and it resulted in a run-time error. Here's my code: #include <iostream> using namespace std; int main() { cout << "Hello world!" << endl; system("pause"); return 0; } Looks like something is broken (maybe I missed something?). It gets a runtime error at line 7: http://img443