Read in enum types

[Alex]

Hi,

I want to read in enum types from standard input. Unfortunately it does not
work. The code is given as follows:

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

using namespace std;

enum TYP { eins, zwei, drei};

int main()
{
Â*Â*Â*Â*stringÂ*input("datIn");
Â*Â*Â*Â*ifstreamÂ*IN(input.c_str());
Â*Â*Â*Â*TYPÂ*t;

Â*Â*Â*Â*cinÂ*>>Â*t;Â*Â*//Â*Fehlermeldung

Â*Â*Â*Â*returnÂ*0;
}

Do I have to define an input operator ?

Thank you for your help.

[dasjotre]

Alex wrote:

Hi,

I want to read in enum types from standard input. Unfortunately it does not
work. The code is given as follows:

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

using namespace std;

enum TYP { eins, zwei, drei};

int main()
{
string input("datIn");
ifstream IN(input.c_str());
TYP t;

cin >t; // Fehlermeldung

return 0;
}

Do I have to define an input operator ?

You could read an int and convert it to TYP

[Haro Panosyan]

Alex wrote:

Hi,

I want to read in enum types from standard input. Unfortunately it does not
work. The code is given as follows:

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

using namespace std;

enum TYP { eins, zwei, drei};

int main()
{
string input("datIn");
ifstream IN(input.c_str());

As a side note, you can directly do this, instead of above 2 lines
ifstream IN("datIn);

TYP t;

cin >t; // Fehlermeldung

return 0;
}

Do I have to define an input operator ?

Thank you for your help.

[Ondra Holub]

Alex napsal:

Hi,

I want to read in enum types from standard input. Unfortunately it does not
work. The code is given as follows:

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

using namespace std;

enum TYP { eins, zwei, drei};

int main()
{
string input("datIn");
ifstream IN(input.c_str());
TYP t;

cin >t; // Fehlermeldung

return 0;
}

Do I have to define an input operator ?

Thank you for your help.

It depends on format in which is your enum written in the stream.
Anyway you should overload input operator>>:

template<typename T, typename TRAITS>
std::basic_istream<T, TRAITS>& operator>>(std::basic_istream<T,
TRAITS>& is, TYP& data)
{
// Here read your type from is any way you want.
// One possible (of many) example follows:

std::basic_string<Ts;
is >s;

// Here would be better some searching mechanism or table for
bigger enums
if (s == "eins") data = eins;
else if (s == "zwei") data = zwei;
else if (s == "drei") data = drei;
else
{
// Wrong input - do what ever you want, but you should switch
is into bad state
}

return is;
}

It is written from scratch, so there may be some typos.

[Alex]

Thank you for your suggestions. I'll try them out.