std::boolalpha, std::noboolalpha

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Input/output library

I/O manipulators

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

strstreambuf (deprecated)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

istrstream (deprecated)

ostrstream (deprecated)

strstream (deprecated)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

Input/output manipulators

Floating-point formatting
showpointnoshowpoint setprecision	fixedscientifichexfloatdefaultfloat (C++11)(C++11)
Integer formatting
setbase showbasenoshowbase	dechexoct
Boolean formatting
boolalphanoboolalpha
Field width and fill control
setfill setw	internalleftright
Other formatting
showposnoshowpos	uppercasenouppercase
Whitespace processing
ws ends	skipwsnoskipws
Output flushing
flush endl	unitbufnounitbuf
Status flags manipulation
resetiosflags	setiosflags
Time and money I/O
get_money (C++11) get_time (C++11)	put_money (C++11) put_time (C++11)
Quoted manipulator
quoted (C++14)

 

Defined in header <ios>
std::ios_base& boolalpha( std::ios_base& str );	(1)
std::ios_base& noboolalpha( std::ios_base& str );	(2)

1) Enables the boolalpha flag in the stream str as if by calling str.setf(std::ios_base::boolalpha)

2) Disables the boolalpha flag in the stream str as if by calling str.unsetf(std::ios_base::boolalpha)

std::boolalpha is an I/O manipulator, so it may be called with an expression such as out << std::boolalpha for any out of type std::basic_ostream or with an expression such as in >> std::boolalpha for any in of type std::basic_istream.

Parameters

str

-

reference to I/O stream

Return value

str (reference to the stream after manipulation)

Example

Run this code

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

Output:

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

See also

resetiosflags	clears the specified ios_base flags (function)
setiosflags	sets the specified ios_base flags (function)
do_truenamedo_falsename [virtual]	provides the string to use as the name of the boolean true and false (virtual protected member function of std::numpunct)