c++ - eof() bad practice? -

possible duplicate:
why iostream::eof inside loop condition considered wrong?

so i've been using eof() function in lot of programs require file input, , professor said fine use few people on have said shouldn't use without specifying reason. wondering, there reason?

you can use eof test exact condition reports - whether have attempted read past end of file. cannot use test whether there's more input read, or whether reading succeeded, more common tests.

wrong:

while (!cin.eof()) {   cin >> foo; } 

correct:

if (!(cin >> foo)) {   if (cin.eof()) {     cout << "read failed due eof\n";   } else {     cout << "read failed due other eof\n";   } }