I've been using manipulators for some time without fully understand how they work.
This code:
std::cout << std::hex << std::showbase;
std::cout << std::uppercase << 77 << '\n';
std::cout << std::nouppercase << 77 << '\n';
Or alternatively this:
std::cout << std::hex;
std::cout << std::setiosflags(std::ios::showbase | std::ios::uppercase) << 77 << '\n';
std::cout << std::nouppercase << 77 << '\n';
Both outputs this:
0X4D // 'X' and 'D' uppercase
0x4d // 'x' and 'd' lowercase
However none of the following lines of code can convert the string "abcd" to uppercase. Why?
std::cout << std::uppercase << "abcd" << '\n';
std::cout << std::setiosflags(std::ios::uppercase) << "abcd" << '\n';
Another question is why showbase and uppercase must be qualified with std::ios:: inside std::setiosflags() and only with std:: outside that function?
Finaly, why std::hex can't be accepted inside std::setiosflags()
Thank you
Read the documentation for std::uppercase.
Enables the use of uppercase characters in floating-point and hexadecimal integer output.
std::ios_base::hex is accepted by std::setiosflags there is an example in the docs.
Here is the example for std::uppercase:
#include <iostream>
int main()
{
std::cout << std::hex << std::showbase
<< "0x2a with uppercase: " << std::uppercase << 0x2a << '\n'
<< "0x2a with nouppercase: " << std::nouppercase << 0x2a << '\n'
<< "1e-10 with uppercase: " << std::uppercase << 1e-10 << '\n'
<< "1e-10 with nouppercase: " << std::nouppercase << 1e-10 << '\n';
}
Here is the example for std::setiosflags:
#include <iostream>
#include <iomanip>
int main()
{
std::cout << std::resetiosflags(std::ios_base::dec)
<< std::setiosflags( std::ios_base::hex
| std::ios_base::uppercase
| std::ios_base::showbase) << 42 << '\n';
}
The definitions:
std::hex is defined as std::ios_base& hex( std::ios_base& str );
std::ios_base::hex is defined as static constexpr fmtflags hex = /*...*/;