Print boolean in C++ [using std::boolalpha and std::noboolalpha]

In this article, we have presented how to print boolean values in C++ (as integer and text) and explored the concepts of std::boolalpha and std::noboolalpha.

Table of contents:

1. Print boolean in C++ by default
2. std::boolalpha
3. std::noboolalpha
4. Conclusion

Print boolean in C++ by default

Boolean values are interpreted by cout in C++ as integers. As true is mapped to 1 and false is mapped to 0. This is by default and can be changed.

Following C++ code illustrates the concept:

#include <iostream>
int main()
{
  std::cout << false << std::endl;
  std::cout << true << std::endl;
}

Output:

0
1

std::boolalpha

std::boolalpha is an I/O manipulator that can be passed to cout to change the way boolean values are interpreted by cout.

When std::boolalpha is passed to cout, boolean values are treated as string values. true is interpreted as "true" and false is interpreted as "false".

std::cout << std::boolalpha << true << std::endl;

If we set the following:

std::cout << std::boolalpha;

Then, all cout following the above line will consider that boolaplha is already set. To revert to the original behavior, one need to set:

std::cout << std::noboolalpha;

Following C++ code illustrates the concept:

#include <iostream>
int main()
{
  std::cout << std::boolalpha << false << std::endl;
  std::cout << std::boolalpha << true << std::endl;
}

Output:

0
1

std::noboolalpha

Similar to std::boolalpha, std::noboolalpha is an I/O manipulator that enables cout to treat boolean values as integer values. This is the default behaviour.

std::cout << std::noboolalpha << false << std::endl;

Following C++ code illustrates the concept:

#include <iostream>
int main()
{
  std::cout << std::noboolalpha << false << std::endl;
  std::cout << std::noboolalpha << true << std::endl;
}

Output:

0
1

Conclusion

Following C++ code summarizes the idea of printing boolean using cout:

#include <iostream>
int main()
{
  std::cout << false << std::endl;
  std::cout << std::boolalpha << false << std::endl;
  std::cout << true << std::endl;
  std::cout << std::boolalpha << true << std::endl;
  std::cout << std::noboolalpha << true << std::endl;
  std::cout << std::noboolalpha << false << std::endl;
}

Output:

0
false
1
true
1
0

With this article at OpenGenus, you must have the complete idea of how to print boolean in C++.