std::showpoint 显示小数点

std::showpoint

ios_base& showpoint (ios_base& str);

Show decimal point

Sets the  showpoint format flag for the  str stream.

When the  showpoint format flag is set, the decimal point is always written for floating point values inserted into the stream (even for those whose decimal part is zero). Following the decimal point, as many digits as necessary are written to match the  precision set for the stream (if any).

This flag can be unset with the  noshowpoint manipulator. When not set, the decimal point is only written for numbers whose decimal part is not zero.

The precision setting can be modified using the  precision member function.

For standard streams, the  showpoint flag is  not set on initialization.