std:: showbase, std:: noshowbase

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

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

#include <iomanip>
#include <iostream>
#include <locale>
#include <sstream>
 
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';
}

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

See also