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.
| str | - | reference to I/O stream |
str (reference to the stream after manipulation).
#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
| changes the base used for integer I/O (function) |
|
| controls whether prefix is used to indicate numeric base (function) |
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