C++ Manipulator noboolalpha

C++ manipulator noboolalpha function is used to set the output stream to display bool values as integers 0 or 1 (i.e. the default setting).

Syntax

Parameter

str: stream object whose format flag is affected.

Return value

It returns argument str.

Data Races

Data races may be occurred when modified str concurrent accesses to the same stream object.

Exceptions

str is in a valid state, if an exception is thrown.

Example 1

Let's see the simple example to demonstrate the use of noboolalpha:

#include <iostream>     // std::cout, std::boolalpha, std::noboolalpha

using namespace std;

int main () {
  bool b = true;
  cout <<"When we use boolalpha then b = " <<boolalpha << b << '\n';
  cout <<"When we use noboolalpha then b = " <<noboolalpha << b << '\n';
  return 0;
}

Output:

When we use boolalpha then b = true
When we use noboolalpha then b = 1

Example 2

Let's see another simple example:

#include <sstream>
#include <locale>
#include <iostream>

using namespace std;

int main()
{
    // boolalpha output
    cout << boolalpha 
              << "boolalpha true: " << true << '\n'
              << "boolalpha false: " << false << '\n';
    cout << noboolalpha 
              << "noboolalpha true: " << true << '\n'
              << "noboolalpha false: " << false << '\n';
    // booalpha parse
    bool b1, b2;
    istringstream is("true false");
    is >> boolalpha >> b1 >> b2;
    cout << '\"' << is.str() << "\" parsed as " << b1 << ' ' << b2 << '\n';
    
return 0;
}

Output:

boolalpha true: true
boolalpha false: false
noboolalpha true: 1
noboolalpha false: 0
"true false" parsed as 1 0

Example 3

Let's see another simple example:

#include <sstream>
#include <locale>
#include <iostream>

using namespace std;

int main()
{
    // boolalpha output
    cout << boolalpha 
              << "boolalpha true: " << true << '\n'
              << "boolalpha false: " << false << '\n';
    cout << noboolalpha 
              << "noboolalpha true: " << true << '\n'
              << "noboolalpha false: " << false << '\n';
    // booalpha parse
    bool b1, b2;
    istringstream is("true false");
    is >> boolalpha >> b1 >> b2;
    cout << '\"' << is.str() << "\" parsed as " << b1 << ' ' << b2 << '\n';
    
return 0;
}

Output:

booleanValue is 1
booleanValue (after using boolalpha) is true

switch booleanValue and use noboolalpha

booleanValue is 0
booleanValue (after using boolalpha) is false

Next TopicC++ Manipulator

← prev next →