strange behavior at switch directive

[nuderobmonkey]

I'm wondering why at the below code within the switch directive the 'default' branch will executed at line 26. That should never happen if the input file supplies correct formatted data.

#include <iostream>
#include <fstream>
#include <vector>
#include <exception>

enum class Note { A, B, C, D, E, F, G };
enum class String { E, A, D, G, B };
struct Pos
{
    Note m_note;
    int m_fret;
    String m_string;
};

std::istream & operator>>( std::istream & is, String & string)
{
    std::string tmp;
    is >> tmp;
    switch(tmp[0])
    {
        case 'E': string = String::E; break;
        case 'A': string = String::A; break;
        case 'D': string = String::D; break;
        case 'G': string = String::G; break;
        case 'B': string = String::B; break;
        default:
            //std::cout << (int)tmp[0];
            throw std::runtime_error("Wrong_string:"+tmp+"!");
    }
    return is;
}
std::istream & operator>>( std::istream & is, Note & note)
{
    std::string tmp;
    is >> tmp;
    switch(tmp[0])
    {
        case 'A': note = Note::A; break;
        case 'B': note = Note::B; break;
        case 'C': note = Note::C; break;
        case 'D': note = Note::D; break;
        case 'E': note = Note::E; break;
        case 'F': note = Note::F; break;
        case 'G': note = Note::G; break;
        default:
            throw std::runtime_error("Wrong_note:"+tmp+"!");
    }
    return is; 
}
std::istream & operator>>( std::istream & is, Pos & pos)
{
    is >> pos.m_string >> pos.m_fret >> pos.m_note;
    return is;
}

int main()
{
    std::ifstream ifs("notes_on_frets.txt");
    Pos pos;
    std::vector<Pos> pos_v;
    while( ifs >> pos) pos_v.push_back(pos);
}

A short sample of notes_on_frets.txt file:
E 0 E
E 1 F
E 3 G
E 5 A
E 7 B
E 8 C
Any idea what's going wrong?

[helios]

On lines 18, 35, and for >> pos.m_fret on line 52 you're not checking whether anything was read correctly. What happens when you reach the end of input?

[nuderobmonkey]

What fix would you suggest?

I've tried changing line 61 to:

    while( ifs.good() )
    {
        ifs >> pos;
         pos_v.push_back(pos);
     }
}

for fetching the eof, but this doesn't work :(

*edit:
Now I test the stream before the swiches will executed and letting the streams immediately return if input couldn't read and it works fine.

[Cubbi]

Remember to change line 61 back. What you had was correct, the while(ifs.good()) replacement is wrong.