NAME¶

std::dec,std::hex,std::oct - std::dec,std::hex,std::oct

Synopsis¶

Defined in header <ios>
std::ios_base& dec( std::ios_base& str ); (1)
std::ios_base& hex( std::ios_base& str ); (2)
std::ios_base& oct( std::ios_base& str ); (3)

Modifies the default numeric base for integer I/O.

1) sets the basefield of the stream str to dec as if by calling
str.setf(std::ios_base::dec, std::ios_base::basefield)

2) sets the basefield of the stream str to hex as if by calling
str.setf(std::ios_base::hex, std::ios_base::basefield)

3) sets the basefield of the stream str to oct as if by calling
str.setf(std::ios_base::oct, std::ios_base::basefield)

This is an I/O manipulator. It may be called with an expression such as out <<
std::hex for any out of type std::basic_ostream or with an expression such as in >>
std::hex 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 <iostream>
#include <sstream>
#include <bitset>
int main()
{
std::cout << "The number 42 in octal: " << std::oct << 42 << '\n'
<< "The number 42 in decimal: " << std::dec << 42 << '\n'
<< "The number 42 in hex: " << std::hex << 42 << '\n';
int n;
std::istringstream("2A") >> std::hex >> n;
std::cout << std::dec << "Parsing \"2A\" as hex gives " << n << '\n';
// the output base is sticky until changed
std::cout << std::hex << "42 as hex gives " << 42
<< " and 21 as hex gives " << 21 << '\n';

// Note: there is no I/O manipulator that sets up a stream to print out
// numbers in binary format (e.g. bin). If binary output is necessary
// the std::bitset trick can be used:
std::cout << "The number 42 in binary: " << std::bitset<8>{42} << '\n';
}

Output:¶

The number 42 in octal: 52
The number 42 in decimal: 42
The number 42 in hex: 2a
Parsing "2A" as hex gives 42
42 as hex gives 2a and 21 as hex gives 15
The number 42 in binary: 00101010

See also¶

setbase changes the base used for integer I/O
(function)
showbase controls whether prefix is used to indicate numeric base
noshowbase (function)