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

< cpp‎ | io‎ | manip
Input/output manipulators
Floating-point formatting
Integer formatting
Boolean formatting
Field width and fill control
Other formatting
Whitespace processing
Output flushing

Status flags manipulation
Time and money I/O
Quoted manipulator
Defined in header <ios>

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.


[edit] Parameters

str - reference to I/O stream

[edit] Return value

str (reference to the stream after manipulation).

[edit] Example

#include <bitset>
#include <iostream>
#include <sstream>
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';


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

[edit] See also

changes the base used for integer I/O
(function) [edit]
controls whether prefix is used to indicate numeric base
(function) [edit]