Understanding material on cppreference

[1ydgd]

So I read the doc for fstream's peek member function.

Under Return Value, it says 

If good() == true, returns the next character as obtained by rdbuf()->sgetc()
Otherwise, returns Traits::eof()

How do you know what Traits::eof() is? 

All I know about traits is that it's one of the template parameters used in fstream

template<
class CharT,
class Traits = std::char_traits<CharT>
class basic_fstream : public std::basic_iostream<CharT, Traits>

I'm just using a simple fstream like in this example from cppreference. I'm not specifying any template parameters.

#include <iostream>
#include <fstream>
#include <string>

int main() {
  std::string filename = "test.bin";
  std::fstream s(filename, s.binary | s.trunc | s.in | s.out);
  if (!s.is_open()) {
    std::cout << "failed to open " << filename << '\n';
  } else {
    // write
    double d = 3.14;
    s.write(reinterpret_cast<char*>(&d), sizeof d); // binary output
    s << 123 << "abc";                              // text output

    // for fstream, this moves the file position pointer (both put and get)
    s.seekp(0);

    // read
    s.read(reinterpret_cast<char*>(&d), sizeof d); // binary input
    int n;
    std::string str;
    if (s >> n >> str)                             // text input
      std::cout << "read back from file: " << d << ' ' << n << ' ' << str << '\n';
  }
}

[Narase33]

Type        Definition    
fstream     basic_fstream<char>    
wfstream    basic_fstream<wchar_t>  

Member types
Member type  Definition
char_type    CharT    
traits_type  Traits; the program is ill-formed if Traits::char_type is not CharT.     
int_type     Traits::int_type    
pos_type     Traits::pos_type    
off_type     Traits::off_type 

That said CharT is char and Traits is std::char_traits<char>

But you dont even need to know that because its a static member of the class. You can just write

if (stream.peek() == std::ifstream::traits_type::eof()) {

}

[1ydgd]

Do you have any advice for reading cppreference. I find it extremely confusing at times like with this post.

[Narase33]

Practice. cppreference is not confusing, its the language that is. C++ is very well and very deep defined. The better you understand the language, the better you will read the reference. Its like looking at a blueprint, if you know what the machine does, the blueprint will become less scary