std::defaultfloat

ios_base& defaultfloat (ios_base& str);

Use default floating-point notation

Sets the floatfield format flag for the str stream to defaultfloat.

When floatfield is set to defaultfloat, floating-point values are written using the default notation: the representation uses as many meaningful digits as needed up to the stream's decimal precision (precision), counting both the digits before and after the decimal point (if any).

The floatfield format flag is both a selective and a toggle flag: it can take any of the following values, or none:

flag value	effect when set
`fixed`	write floating-point values in fixed-point notation.
`scientific`	write floating-point values in scientific notation.
`hexfloat`	write floating-point values in hexadecimal format. The value of this is the same as `(fixed\|scientific)`
`defaultfloat`	write floating-point values in default floating-point notation. This is the value by default (same as none, before any other `floatfield` bit is set).

For standard streams, the floatfield format flag is set to this value (defaultfloat) on initialization.

Parameters

str: Stream object whose floatfield format flag is affected.
Because this function is a manipulator, it is designed to be used alone with no arguments in conjunction with the insertion (<<) and extraction (>>) operations on streams (see example below).

Return Value

Argument str.

Example

// hexfloat floatfield
#include <iostream>     // std::cout, std::hexfloat, std::defaultfloat

int main () {
  double a = 3.1415926534;
  double b = 2006.0;
  double c = 1.0e-10;

  std::cout.precision(5);

  std::cout << "hexfloat:\n" << std::hexfloat;
  std::cout << a << '\n' << b << '\n' << c << '\n';

  std::cout << '\n';

  std::cout << "defaultfloat:\n" << std::defaultfloat;
  std::cout << a << '\n' << b << '\n' << c << '\n';

  return 0;
}

Possible output:

hexfloat:
0x1.921fb5p+1
0x1.f58000p+10
0x1.b7cdfep-34

defaultfloat:
3.14159
2006
1e-010

Data races

Modifies str. Concurrent access to the same stream object may cause data races.

Exception safety

Basic guarantee: if an exception is thrown, str is in a valid state.

types

manipulators

other functions