# std::fixed, std::scientific, std::hexfloat, std::defaultfloat

From cppreference.com
< cpp‎ | io‎ | manip

Defined in header `<ios>` |  |
std::ios_base& fixed( std::ios_base& str ); | (1) |
std::ios_base& scientific( std::ios_base& str ); | (2) |
std::ios_base& hexfloat( std::ios_base& str ); | (3) | (since C++11)
std::ios_base& defaultfloat( std::ios_base& str ); | (4) | (since C++11)

Modifies the default formatting for floating-point output.

1) Sets the `floatfield` of the stream `str` to `fixed` as if by calling str.setf(std::ios_base::fixed, std::ios_base::floatfield)
2) Sets the `floatfield` of the stream `str` to `scientific` as if by calling str.setf(std::ios_base::scientific, std::ios_base::floatfield)
3) Sets the `floatfield` of the stream `str` to `fixed` and `scientific` simultaneously as if by calling str.setf(std::ios_base::fixed | std::ios_base::scientific, std::ios_base::floatfield). This enables hexadecimal floating-point formatting.
4) Sets the `floatfield` of the stream `str` to zero, as if by calling str.unsetf(std::ios_base::floatfield). This enables the default floating-point formatting, which is different from fixed and scientific.

This is an I/O manipulator, it may be called with an expression such as out << std::fixed for any `out` of type std::basic_ostream (or with an expression such as in >> std::scientific for any `in` of type std::basic_istream).

### Parameters

str | - | reference to I/O stream

### Return value

`str` (reference to the stream after manipulation)

### Notes

Hexadecimal floating-point formatting ignores the stream precision specification, as required by the specification of std::num_put::do_put.

These manipulators do not affect floating-point parsing.

### Example

Run this code

    #include <iostream>
    #include <iomanip>
    #include <sstream>

    enum class cap { title, middle, end };
    void print(const char* text, double num, cap c)
    {
        if (c == cap::title) std::cout <<
        "┌──────────┬────────────┬──────────────────────────┐\n"
        "│  number  │   iomanip  │      representation      │\n"
        "├──────────┼────────────┼──────────────────────────┤\n"
        ;
        std::cout << std::left
        << "│ " << std::setw(8) << text << " │ fixed      │ "
        << std::setw(24) << std::fixed        << num << " │\n"
        << "│ " << std::setw(8) << text << " │ scientific │ "
        << std::setw(24) << std::scientific   << num << " │\n"
        << "│ " << std::setw(8) << text << " │ hexfloat   │ "
        << std::setw(24) << std::hexfloat     << num << " │\n"
        << "│ " << std::setw(8) << text << " │ default    │ "
        << std::setw(24) << std::defaultfloat << num << " │\n"
        ;
        std::cout << (c != cap::end ?
        "├──────────┼────────────┼──────────────────────────┤\n" :
        "└──────────┴────────────┴──────────────────────────┘\n" );
    }

    int main()
    {
        print("0.0", 0.0, cap::title);
        print("0.01", 0.01, cap::middle);
        print("0.00001", 0.00001, cap::end);

        // Note; choose clang for correct output
        double f;
        std::istringstream("0x1.8p+0") >> f;
        std::cout << "Parsing 0x1.8p+0 gives " << f << '\n';

        std::istringstream("0x1P-1022") >> f;
        std::cout << "Parsing 0x1P-1022 gives " << f << '\n';
    }

Output:

    ┌──────────┬────────────┬──────────────────────────┐
    │  number  │   iomanip  │      representation      │
    ├──────────┼────────────┼──────────────────────────┤
    │ 0.0      │ fixed      │ 0.000000                 │
    │ 0.0      │ scientific │ 0.000000e+00             │
    │ 0.0      │ hexfloat   │ 0x0p+0                   │
    │ 0.0      │ default    │ 0                        │
    ├──────────┼────────────┼──────────────────────────┤
    │ 0.01     │ fixed      │ 0.010000                 │
    │ 0.01     │ scientific │ 1.000000e-02             │
    │ 0.01     │ hexfloat   │ 0x1.47ae147ae147bp-7     │
    │ 0.01     │ default    │ 0.01                     │
    ├──────────┼────────────┼──────────────────────────┤
    │ 0.00001  │ fixed      │ 0.000010                 │
    │ 0.00001  │ scientific │ 1.000000e-05             │
    │ 0.00001  │ hexfloat   │ 0x1.4f8b588e368f1p-17    │
    │ 0.00001  │ default    │ 1e-05                    │
    └──────────┴────────────┴──────────────────────────┘
    Parsing 0x1.8p+0 gives 1.5
    Parsing 0x1P-1022 gives 2.22507e-308

### See also

setprecision | changes floating-point precision (function)

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