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copied!<p>It is very easy to differentiate between EOF and other errors, as long as you don't configure the stream to use exceptions.</p> <p>Simply check <code>stream.eof()</code> at the end.</p> <p>Before that only check for failure/non-failure, e.g. <code>stream.fail()</code> or <code>!stream</code>. Note that <code>good</code> is not the opposite of <code>fail</code>. So in general never even look at the <code>good</code>, only at the <code>fail</code>.</p> <hr> <p><strong>Edit:</strong></p> <p>Some example code, namely your example modified to distinguish an ungood bool specification in the data:</p> <pre><code>#include <iostream> #include <sstream> #include <string> #include <stdexcept> using namespace std; bool throwX( string const& s ) { throw runtime_error( s ); } bool hopefully( bool v ) { return v; } bool boolFrom( string const& s ) { istringstream stream( s ); (stream >> boolalpha) || throwX( "boolFrom: failed to set boolalpha mode." ); bool result; (stream >> result) || throwX( "boolFrom: failed to extract 'bool' value." ); char c; stream >> c; hopefully( stream.eof() ) || throwX( "boolFrom: found extra characters at end." ); return result; } void readbools( istream& is ) { string word; while( is >> word ) { try { bool const b = boolFrom( word ); cout << (b ? "T" : "F") << endl; } catch( exception const& x ) { cerr << "!" << x.what() << endl; } } cout << "- " << is.good() << is.eof() << is.fail() << is.bad() << "\n"; } void testread( string const& s ) { istringstream is( s ); readbools( is ); } int main() { cout << string( 60, '-' ) << endl; testread( "true false" ); cout << string( 60, '-' ) << endl; testread( "true false tr" ); cout << string( 60, '-' ) << endl; testread( "true false truex" ); } </code></pre> <p>Example result:</p> <pre> ------------------------------------------------------------ T F - 0110 ------------------------------------------------------------ T F !boolFrom: failed to extract 'bool' value. - 0110 ------------------------------------------------------------ T F !boolFrom: found extra characters at end. - 0110 </pre> <hr> <p><strong>Edit 2</strong>: in the posted code and results, added example of using <code>eof()</code> checking, which I forgot.</p> <hr> <p><strong>Edit 3</strong>: The following corresponding example uses the OP’s proposed skip-whitespace-before-reading solution:</p> <pre><code>#include <iostream> #include <sstream> #include <string> using namespace std; void readbools( istream& is ) { bool b; while( is >> ws && !is.eof() && is >> b ) // <- Proposed scheme. { cout << (b ? "T" : "F") << endl; } if( is.fail() ) { cerr << "!readbools: failed to extract 'bool' value." << endl; } cout << "- " << is.good() << is.eof() << is.fail() << is.bad() << "\n"; } void testread( string const& s ) { istringstream is( s ); is >> boolalpha; readbools( is ); } int main() { cout << string( 60, '-' ) << endl; testread( "true false" ); cout << string( 60, '-' ) << endl; testread( "true false tr" ); cout << string( 60, '-' ) << endl; testread( "true false truex" ); } </code></pre> <p>Example result:</p> <pre> ------------------------------------------------------------ T F - 0100 ------------------------------------------------------------ T F !readbools: failed to extract 'bool' value. - 0110 ------------------------------------------------------------ T F T !readbools: failed to extract 'bool' value. - 0010 </pre> <p>The main difference is that this approach produces 3 successfully read values in the third case, even though the third value is incorrectly specified (as <code>"truex"</code>).</p> <p>I.e. it fails to recognize an incorrect specification as such.</p> <p>Of course, my ability to write Code That Does Not Work™ is no proof that it can not work. But I am fairly good at coding up things, and I could not see any way to detect the <code>"truex"</code> as incorrect, with this approach (while it was easy to do with the read-words exception based approach). So at least for me, the read-words exception based approach is simpler, in the sense that it is easy to make it behave correctly.</p> <p>Cheers & hth.,</p>

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