How does one buffer output in C++ with new lines

Question

I have some code that takes in a paragraph and starts a new line after every sentence.

I would like to buffer the output in the terminal with a new line, but adding "std::cout << endl;" outside of the loop does not seem to work. Any help in separating the input from the output if it is typed into a terminal.

I have commented out the code I expected to work, but which does not.

#include <iostream>
#include <string>
using namespace std;

int main() {

  // std::cout << std::endl;

  for (;;) {
    string line;
    getline(std::cin, line);
    if (!cin) {
      break;
    }
    for (unsigned int i = 0; i < line.length(); ++i) {
      const string text = line.substr(i, 1);
      if (text == "." || text == "?" || text == "!") {
          std::cout << text;
          std::cout << std::endl;
      }else{
          std::cout << text;
      }
    }
  }

  // std::cout << std::endl;

  return 0;
}

Possible duplicate of [Flushing of cout prior to reading input using cin .. why?](http://stackoverflow.com/questions/2704752/flushing-of-cout-prior-to-reading-input-using-cin-why) — Barmar, Jan 19 '17 at 00:18
I tried to flush "cout" with a type before each new push of a new line, but that doesn't seem to allow a new line to be created first still. — Vyff, Jan 19 '17 at 00:34
@CodingPig is almost right. If you want an extra line before input, I think all you need to do is move the commented-out line up one brace. — user4581301, Jan 19 '17 at 00:35
While that works, then it is in the loop and executes before every sentence but I only want it before the paragraph. — Vyff, Jan 19 '17 at 00:39
I recommend learning to use the debugging software that almost certainly came with your debugger. With it you can control the execution of your code, slowing down to line by line if you want to so you can watch the program run and see what it does. You can inspect the variables as well. Very handy. — user4581301, Jan 19 '17 at 00:39
Then you need to find a way to signal a new paragraph that isn't a newline and exit the loop when you find one. Right now the only way out of the loop is to end the console's input. Can't do much after that unless you start the console back up again. — user4581301, Jan 19 '17 at 00:41
Maybe we don't understand the question. I thought you were trying to *prevent* output from being flushed until you read a whole sentence. — Barmar, Jan 19 '17 at 00:43
I made a for loop for the first iteration to add a new line and made the rest covered in its conditions, its inelegant but works for now. — Vyff, Jan 19 '17 at 00:54

score -1 · Accepted Answer · answered Jan 19 '17 at 00:10

-1

The commented line will never work since it will never be called. You have an endless loop for(;;) before it.

answered Jan 19 '17 at 00:10

Coding Pig

66
5

There's a `break` inside the loop. – David Schwartz Jan 19 '17 at 00:12
Does !cin not exit once there is no more to read or does it need an EOF to exit and execute other part of the program? – Vyff Jan 19 '17 at 00:17
The break will be never hit as well - cin is always solid. – Coding Pig Jan 19 '17 at 00:18
@CodingPig When reading from `cin` gets an error or EOF, the `cin` state changes and it becomes falsey. – Barmar Jan 19 '17 at 00:21
This is why you can write things like `while (cin >> variable) { ... }` – Barmar Jan 19 '17 at 00:21
@Vyff `!cin` is `false`, always so it will never break out. – Coding Pig Jan 19 '17 at 00:22
@CodingPig Why don't you just try running the program, you'll see that the loop ends when you type the EOF character. – Barmar Jan 19 '17 at 00:23
@Vyff it needs an EOF. Press Ctrl-D in *nix or Ctrl-Z in Windows. – user4581301 Jan 19 '17 at 00:26
As I only really need the first buffer, can I execute making a new line before this loop starts? – Vyff Jan 19 '17 at 00:29
@Barmar You guys are right. I didn't think of this scenario while assuming the input from console keeps going. – Coding Pig Jan 19 '17 at 00:51
My overall design of the program for what I wanted was bad – Vyff Jan 19 '17 at 00:57
@Vyff BTW, use `cin.good()` instead of `cin` for checking if the input steam ends - cin operatior >> returns reference of stream so it is semantically better to not assume it could be false. – Coding Pig Jan 19 '17 at 01:03

How does one buffer output in C++ with new lines

1 Answers1