# std::ios_base::precision

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< cpp‎ | io‎ | ios base

streamsize precision() const; | (1) |
streamsize precision( streamsize new_precision ); | (2) |

Manages the precision (i.e. how many digits are generated) of floating point output performed by std::num_put::do_put.

1) Returns the current precision.
2) Sets the precision to the given one. Returns the previous precision.

The default precision, as established by std::basic_ios::init, is 6.

### Parameters

new_precision | - | new precision setting

### Return value

the precision before the call to the function

### Example

Run this code

    #include <iostream>
    int main()
    {
        const double d = 1.2345678901234;
        std::cout << "The  default precision is " << std::cout.precision() << "\n\n";
        std::cout << "With default precision d is " << d << '\n';
        std::cout.precision(12);
        std::cout << "With high    precision d is " << d << '\n';
    }

Output:

    The  default precision is 6

    With default precision d is 1.23457
    With high    precision d is 1.23456789012

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 189 | C++98 | 'precision' was defined as 'the number of digits after the decimal point', but it is not correct in some cases | corrected

### See also

width | manages field width (public member function)
setprecision | changes floating-point precision (function)

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