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# std::setbase

From cppreference.com
< cpp‎ | io‎ | manip

Defined in header `<iomanip>` |  |
/*unspecified*/ setbase( int base ); |  |

Sets the numeric base of the stream. When used in an expression out << setbase(base) or in >> setbase(base), changes the `basefield` flag of the stream `out` or `in`, depending on the value of `base`:

- the value 16 sets `basefield` to std::ios_base::hex
- the value 8 sets std::ios_base::oct
- the value 10 sets std::ios_base::dec.

Values of `base` other than 8, 10, or 16 reset `basefield` to zero, which corresponds to decimal output and prefix-dependent input.

### [edit] Parameters

base | - | new value for basefield

### [edit] Return value

Returns an object of unspecified type such that if `str` is the name of an output stream of type std::basic_ostream<CharT, Traits> or std::basic_istream<CharT, Traits>, then the expression str << setbase(base) or str >> setbase(base) behaves as if the following code was executed:

    str.setf(base ==  8 ? std::ios_base::oct :
                base == 10 ? std::ios_base::dec :
                    base == 16 ? std::ios_base::hex :
                         std::ios_base::fmtflags(0),
             std::ios_base::basefield);

### [edit] Example

Run this code

    #include <iostream>
    #include <sstream>
    #include <iomanip>
    int main()
    {
        std::cout << "Parsing string \"10 0x10 010\"\n";

        int n1, n2, n3;
        std::istringstream s("10 0x10 010");
        s >> std::setbase(16) >> n1 >> n2 >> n3;
        std::cout << "hexadecimal parse: " << n1 << ' ' << n2 << ' ' << n3 << '\n';

        s.clear();
        s.seekg(0);
        s >> std::setbase(0) >> n1 >> n2 >> n3;
        std::cout << "prefix-dependent parse: " << n1 << ' ' << n2 << ' ' << n3 << '\n';

        std::cout << "hex output: " << std::setbase(16)
                  << std::showbase << n1 << ' ' << n2 << ' ' << n3 << '\n';
    }

Output:

    Parsing string "10 0x10 010"
    hexadecimal parse: 16 16 16
    prefix-dependent parse: 10 16 8
    hex output: 0xa 0x10 0x8

### [edit] See also

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

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