std::showbase,std::noshowbase (3) - Linux Manuals

std::showbase,std::noshowbase: std::showbase,std::noshowbase

NAME

std::showbase,std::noshowbase - std::showbase,std::noshowbase

Synopsis

Defined in header <ios>
std::ios_base& showbase( std::ios_base& str ); (1)
std::ios_base& noshowbase( std::ios_base& str ); (2)

1) enables the showbase flag in the stream str as if by calling str.setf(std::ios_base::showbase)
2) disables the showbase flag in the stream str as if by calling str.unsetf(std::ios_base::showbase)
This is an I/O manipulator, it may be called with an expression such as out << std::showbase for any out of type std::basic_ostream or with an expression such as in >> std::showbase for any in of type std::basic_istream.
The showbase flag affects the behavior of integer output (see std::num_put::put), monetary input (see std::money_get::get) and monetary output (see std::money_put::put).

Parameters

str - reference to I/O stream

Return value

str (reference to the stream after manipulation)

Notes

As specifed in std::num_put::put, the showbase flag in integer output acts like the # format specifier in std::printf, which means the numeric base prefix is not added when outputting the value zero.

Example

// Run this code

  #include <sstream>
  #include <locale>
  #include <iostream>
  #include <iomanip>
  int main()
  {
      // showbase affects the output of octals and hexadecimals
      std::cout << std::hex
                << "showbase: " << std::showbase << 42 << '\n'
                << "noshowbase: " << std::noshowbase << 42 << '\n';

      // and both input and output of monetary values
      std::locale::global(std::locale("en_US.utf8"));
      long double val = 0;
      std::istringstream is("3.14");
      is >> std::showbase >> std::get_money(val);
      std::cout << "With showbase, parsing 3.14 as money gives " << val << '\n';
      is.seekg(0);
      is >> std::noshowbase >> std::get_money(val);
      std::cout << "Without showbase, parsing 3.14 as money gives " << val << '\n';
  }

Output:

  showbase: 0x2a
  noshowbase: 2a
  With showbase, parsing 3.14 as money gives 0
  Without showbase, parsing 3.14 as money gives 314