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Dependent name resolution & namespace std / Standard Library
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Closed 8 years ago.
I am trying to construct an ifstream_iterator on pair. My code is as follows:
typedef pair<float, int> T;
istream& operator>>(istream& stream, T& in) {
stream >> in.first >> in.second;
return stream;
}
int main(int argc, char **argv) {
ifstream infile("dummy2");
istream_iterator<T> iit(infile);
istream_iterator<T> eos;
while (iit != eos) {
cout << (*iit).first << endl;
++iit;
}
return 0;
}
I have a dummy file "dummy2" as follows:
"a" 4 "b" 5
I would like to output pairs {"a", 4} and {"b", 5}.
However, I get nasty compilation error
In file included from /usr/include/c++/4.6/iterator:66:0,
from filestream.cpp:9:
/usr/include/c++/4.6/bits/stream_iterator.h: In member function ‘void std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::_M_read() [with _Tp = std::pair<float, int>, _CharT = char, _Traits = std::char_traits<char>, _Dist = long int]’:
/usr/include/c++/4.6/bits/stream_iterator.h:70:9: instantiated from ‘std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::istream_iterator(std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::istream_type&) [with _Tp = std::pair<float, int>, _CharT = char, _Traits = std::char_traits<char>, _Dist = long int, std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::istream_type = std::basic_istream<char>]’
filestream.cpp:32:33: instantiated from here
/usr/include/c++/4.6/bits/stream_iterator.h:121:6: error: no match for ‘operator>>’ in ‘*((std::istream_iterator<std::pair<float, int> >*)this)->std::istream_iterator<std::pair<float, int> >::_M_stream >> ((std::istream_iterator<std::pair<float, int> >*)this)->std::istream_iterator<std::pair<float, int> >::_M_value’
/usr/include/c++/4.6/bits/stream_iterator.h:121:6: note: candidates are:
/usr/include/c++/4.6/istream:122:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:122:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&) {aka std::basic_istream<char>& (*)(std::basic_istream<char>&)}’
/usr/include/c++/4.6/istream:126:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>, std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
/usr/include/c++/4.6/istream:126:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}’
/usr/include/c++/4.6/istream:133:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:133:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘std::ios_base& (*)(std::ios_base&)’
/usr/include/c++/4.6/istream:169:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:169:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘bool&’
/usr/include/c++/4.6/istream:173:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.6/istream:173:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘short int&’
/usr/include/c++/4.6/istream:176:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:176:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘short unsigned int&’
/usr/include/c++/4.6/istream:180:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.6/istream:180:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘int&’
/usr/include/c++/4.6/istream:183:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:183:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘unsigned int&’
/usr/include/c++/4.6/istream:187:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:187:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘long int&’
/usr/include/c++/4.6/istream:191:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:191:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘long unsigned int&’
/usr/include/c++/4.6/istream:196:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:196:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘long long int&’
/usr/include/c++/4.6/istream:200:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:200:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘long long unsigned int&’
/usr/include/c++/4.6/istream:205:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:205:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘float&’
/usr/include/c++/4.6/istream:209:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:209:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘double&’
/usr/include/c++/4.6/istream:213:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:213:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘long double&’
/usr/include/c++/4.6/istream:217:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/usr/include/c++/4.6/istream:217:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘void*&’
/usr/include/c++/4.6/istream:241:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
/usr/include/c++/4.6/istream:241:7: note: no known conversion for argument 1 from ‘std::pair<float, int>’ to ‘std::basic_istream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}’
/usr/include/c++/4.6/bits/basic_string.tcc:998:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.6/bits/random.tcc:923:5: note: template<class _IntType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::uniform_int_distribution<_IntType>&)
/usr/include/c++/4.6/bits/random.tcc:968:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::uniform_real_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:1890:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::cauchy_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.h:3381:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::bernoulli_distribution&)
/usr/include/c++/4.6/bits/random.tcc:1733:5: note: template<class _RealType1, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::normal_distribution<_RealType1>&)
/usr/include/c++/4.6/bits/random.tcc:1063:5: note: template<class _IntType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::geometric_distribution<_IntType>&)
/usr/include/c++/4.6/bits/random.tcc:2085:5: note: template<class _RealType1, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::gamma_distribution<_RealType1>&)
/usr/include/c++/4.6/bits/random.tcc:1622:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::exponential_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:2143:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::weibull_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:2200:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::extreme_value_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:194:5: note: template<class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::linear_congruential_engine<_UIntType, __a, __c, __m>&)
/usr/include/c++/4.6/bits/random.tcc:491:5: note: template<class _UIntType, long unsigned int __w, long unsigned int __n, long unsigned int __m, long unsigned int __r, _UIntType __a, long unsigned int __u, _UIntType __d, long unsigned int __s, _UIntType __b, long unsigned int __t, _UIntType __c, long unsigned int __l, _UIntType __f, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::mersenne_twister_engine<_UIntType, __w, __n, __m, __r, __a, __u, __d, __s, __b, __t, __c, __l, __f>&)
/usr/include/c++/4.6/bits/random.tcc:642:5: note: template<class _UIntType, long unsigned int __w, long unsigned int __s, long unsigned int __r, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::subtract_with_carry_engine<_UIntType, __w, __s, __r>&)
/usr/include/c++/4.6/bits/random.tcc:709:5: note: template<class _RandomNumberEngine, long unsigned int __p, long unsigned int __r, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::discard_block_engine<_RandomNumberEngine, __p, __r>&)
/usr/include/c++/4.6/bits/random.tcc:815:5: note: template<class _RandomNumberEngine, long unsigned int __k, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::shuffle_order_engine<_RandomNumberEngine, __k>&)
/usr/include/c++/4.6/bits/random.tcc:1138:5: note: template<class _IntType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::negative_binomial_distribution<_IntType>&)
/usr/include/c++/4.6/bits/random.tcc:1328:5: note: template<class _IntType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::poisson_distribution<_IntType>&)
/usr/include/c++/4.6/bits/random.tcc:1577:5: note: template<class _IntType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::binomial_distribution<_IntType>&)
/usr/include/c++/4.6/bits/random.tcc:1782:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::lognormal_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:1827:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::chi_squared_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:1936:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::fisher_f_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:1981:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::student_t_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:2308:5: note: template<class _IntType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::discrete_distribution<_IntType>&)
/usr/include/c++/4.6/bits/random.tcc:2488:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::piecewise_constant_distribution<_RealType>&)
/usr/include/c++/4.6/bits/random.tcc:2690:5: note: template<class _RealType, class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::piecewise_linear_distribution<_RealType>&)
/usr/include/c++/4.6/bits/istream.tcc:957:5: note: template<class _CharT2, class _Traits2> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT2*)
/usr/include/c++/4.6/bits/istream.tcc:925:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&)
/usr/include/c++/4.6/istream:709:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char&)
/usr/include/c++/4.6/istream:714:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char&)
/usr/include/c++/4.6/istream:756:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char*)
/usr/include/c++/4.6/istream:761:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char*)
/usr/include/c++/4.6/istream:852:5: note: std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&&, _Tp&) [with _CharT = char, _Traits = std::char_traits<char>, _Tp = std::pair<float, int>] <near match>
/usr/include/c++/4.6/istream:852:5: note: no known conversion for argument 1 from ‘std::istream_iterator<std::pair<float, int> >::istream_type {aka std::basic_istream<char>}’ to ‘std::basic_istream<char>&&’
/usr/include/c++/4.6/iomanip:70:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Resetiosflags)
/usr/include/c++/4.6/iomanip:100:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setiosflags)
/usr/include/c++/4.6/iomanip:131:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setbase)
/usr/include/c++/4.6/iomanip:169:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setfill<_CharT>)
/usr/include/c++/4.6/iomanip:199:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setprecision)
/usr/include/c++/4.6/iomanip:229:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setw)
/usr/include/c++/4.6/iomanip:263:5: note: template<class _CharT, class _Traits, class _MoneyT> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Get_money<_MoneyT>)
make: *** [filestream] Error 1
I cannot quite make sense of what is happening here. Any help is appreciated.
Thanks a lot!
You'll note that simply doing this:
T t;
infile >> t;
Works like a charm! What is up?
std::pair is declared in namespace std.
istream_iterator<> uses operator>> indeed, and it does so using ADL at instantiation time (this is known as two-phase-lookup).
However, at instantiation time, it will not consider your operator>> as it doesn't exist in the namespace that implements istream_iterator and neither was it declared in any of the associated namespaces implied by the arguments (this is the ADL step).
You could be tempted "fix" it by defining your overload in the std namespace (and it works) but that is not allowed by the standard and technically results in Undefined Behaviour.
So you'd do better to introduce a type that allows ADL to kick in:
struct T : public std::pair<int,float> {};
Live On Coliru
#include <utility>
#include <iostream>
#include <iterator>
struct T : std::pair<float, int> {
using std::pair<float, int>::pair;
};
std::istream& operator>>(std::istream& stream, T& in) {
return stream >> in.first >> in.second;
}
int main() {
std::istream_iterator<T> iit(std::cin);
std::istream_iterator<T> eos;
while (iit != eos) {
std::cout << (*iit).first << std::endl;
++iit;
}
}
I suspect that theoretically you should be able to trick thing by reordering includes and injecting the overload early enough so it is "visible" during the first phase of name lookup. However, whether this option is available depends on the implementation and if you're out of luck you still couldn't achieve it without altering the standard library headers (don't do that).
This is a fairly common problem, for which there's no really clean solution. One that normally works is to put your operator into namespace std:
typedef pair<float, int> T;
namespace std {
istream& operator>>(istream& stream, T& in) {
stream >> in.first >> in.second;
return stream;
}
}
int main(int argc, char **argv) {
ifstream infile("dummy2");
istream_iterator<T> iit(infile);
istream_iterator<T> eos;
while (iit != eos) {
cout << (*iit).first << endl;
++iit;
}
return 0;
}
Officially, this gives undefined behavior--you can add some specializations to namespace std, but you can't add overloads there. Unofficially, I've yet to see a compiler/library where it caused a problem.
Related
Isn't this:
operator<<(std::cout, 0);
The same as this?
std::cout<<0;
I tried this piece of code:
#include<iostream>
int main()
{
operator<<(std::cout,0);
return 0;
}
But I got the following error message:
a.cpp: In function ‘int main()’:
a.cpp:11:28: error: call of overloaded ‘operator<<(std::ostream&, int)’ is ambiguous
a.cpp:11:28: note: candidates are:
/usr/include/c++/4.6/ostream:528:5: note: std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const unsigned char*) [with _Traits = std::char_traits<char>]
/usr/include/c++/4.6/ostream:523:5: note: std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const signed char*) [with _Traits = std::char_traits<char>]
/usr/include/c++/4.6/ostream:510:5: note: std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const char*) [with _Traits = std::char_traits<char>]
/usr/include/c++/4.6/bits/ostream.tcc:323:5: note: std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const char*) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.6/ostream:473:5: note: std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, unsigned char) [with _Traits = std::char_traits<char>]
/usr/include/c++/4.6/ostream:468:5: note: std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, signed char) [with _Traits = std::char_traits<char>]
/usr/include/c++/4.6/ostream:462:5: note: std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, char) [with _Traits = std::char_traits<char>]
/usr/include/c++/4.6/ostream:456:5: note: std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char) [with _CharT = char, _Traits = std::char_traits<char>]
Can someone explain it please?
No, it is the same as:
std::cout.operator<<(0);
Using operator<<(std::cout, 0); makes Argument-Dependent Lookup (ADL) kick in, which finds multiple candidates that accept a std::basic_ostream<char> and an int (or a type that has a valid implicit conversion from int) as input. Once ADL kicks in, all of these various overloads become valid candidates.
I was writing a simple piece of c++ code to print out input till the input is not 42. Here is my code:
#include <iostream>
using namespace std;
int main(){
while(true){
int inp;
cin >> inp >> endl;
if(inp == 42){
break;
}
cout << inp << endl;
}
return 0;
}
However when I compile it ,I get a list of errors:
testlife.cpp: In function ‘int main()’:
testlife.cpp:9:14: error: no match for ‘operator>>’ (operand types are ‘std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}’ and ‘<unresolved overloaded function type>’)
cin >> inp >> endl;
~~~~~~~~~~~^~~~~~~
In file included from /usr/include/c++/6/iostream:40:0,
from testlife.cpp:2:
/usr/include/c++/6/istream:120:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(__istream_type& (*__pf)(__istream_type&))
^~~~~~~~
/usr/include/c++/6/istream:120:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&) {aka std::basic_istream<char>& (*)(std::basic_istream<char>&)}’
/usr/include/c++/6/istream:124:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>; std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
operator>>(__ios_type& (*__pf)(__ios_type&))
^~~~~~~~
/usr/include/c++/6/istream:124:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}’
/usr/include/c++/6/istream:131:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(ios_base& (*__pf)(ios_base&))
^~~~~~~~
/usr/include/c++/6/istream:131:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::ios_base& (*)(std::ios_base&)’
/usr/include/c++/6/istream:168:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(bool& __n)
^~~~~~~~
/usr/include/c++/6/istream:168:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘bool&’
/usr/include/c++/6/istream:172:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]
operator>>(short& __n);
^~~~~~~~
/usr/include/c++/6/istream:172:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘short int&’
/usr/include/c++/6/istream:175:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(unsigned short& __n)
^~~~~~~~
/usr/include/c++/6/istream:175:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘short unsigned int&’
/usr/include/c++/6/istream:179:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]
operator>>(int& __n);
^~~~~~~~
/usr/include/c++/6/istream:179:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘int&’
/usr/include/c++/6/istream:182:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(unsigned int& __n)
^~~~~~~~
/usr/include/c++/6/istream:182:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘unsigned int&’
/usr/include/c++/6/istream:186:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(long& __n)
^~~~~~~~
/usr/include/c++/6/istream:186:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long int&’
/usr/include/c++/6/istream:190:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(unsigned long& __n)
^~~~~~~~
/usr/include/c++/6/istream:190:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long unsigned int&’
/usr/include/c++/6/istream:195:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(long long& __n)
^~~~~~~~
/usr/include/c++/6/istream:195:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long long int&’
/usr/include/c++/6/istream:199:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(unsigned long long& __n)
^~~~~~~~
/usr/include/c++/6/istream:199:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long long unsigned int&’
/usr/include/c++/6/istream:214:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(float& __f)
^~~~~~~~
/usr/include/c++/6/istream:214:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘float&’
/usr/include/c++/6/istream:218:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(double& __f)
^~~~~~~~
/usr/include/c++/6/istream:218:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘double&’
/usr/include/c++/6/istream:222:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(long double& __f)
^~~~~~~~
/usr/include/c++/6/istream:222:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long double&’
/usr/include/c++/6/istream:235:7: note: candidate: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
operator>>(void*& __p)
^~~~~~~~
/usr/include/c++/6/istream:235:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘void*&’
/usr/include/c++/6/istream:259:7: note: candidate: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
operator>>(__streambuf_type* __sb);
^~~~~~~~
/usr/include/c++/6/istream:259:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_istream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}’
In file included from /usr/include/c++/6/string:53:0,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/ostream:38,
from /usr/include/c++/6/iostream:39,
from testlife.cpp:2:
/usr/include/c++/6/bits/basic_string.tcc:1437:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)
operator>>(basic_istream<_CharT, _Traits>& __in,
^~~~~~~~
/usr/include/c++/6/bits/basic_string.tcc:1437:5: note: template argument deduction/substitution failed:
testlife.cpp:9:17: note: couldn't deduce template parameter ‘_Alloc’
cin >> inp >> endl;
^~~~
In file included from /usr/include/c++/6/iostream:40:0,
from testlife.cpp:2:
/usr/include/c++/6/istream:799:5: note: candidate: std::basic_istream<_CharT2, _Traits2>& std::operator>>(std::basic_istream<_CharT2, _Traits2>&, _CharT2*) [with _CharT2 = char; _Traits2 = std::char_traits<char>; _CharT = char; _Traits = std::char_traits<char>]
operator>>(basic_istream<char>& __in, char* __s);
^~~~~~~~
/usr/include/c++/6/istream:799:5: note: no known conversion for argument 2 from ‘<unresolved overloaded function type>’ to ‘char*’
In file included from /usr/include/c++/6/istream:934:0,
from /usr/include/c++/6/iostream:40,
from testlife.cpp:2:
/usr/include/c++/6/bits/istream.tcc:923:5: note: candidate: std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&) [with _CharT = char; _Traits = std::char_traits<char>]
operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
^~~~~~~~
/usr/include/c++/6/bits/istream.tcc:923:5: note: no known conversion for argument 2 from ‘<unresolved overloaded function type>’ to ‘char&’
In file included from /usr/include/c++/6/iostream:40:0,
from testlife.cpp:2:
/usr/include/c++/6/istream:756:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char&)
operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
^~~~~~~~
/usr/include/c++/6/istream:756:5: note: template argument deduction/substitution failed:
testlife.cpp:9:17: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘unsigned char&’
cin >> inp >> endl;
^~~~
In file included from /usr/include/c++/6/iostream:40:0,
from testlife.cpp:2:
/usr/include/c++/6/istream:761:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char&)
operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
^~~~~~~~
/usr/include/c++/6/istream:761:5: note: template argument deduction/substitution failed:
testlife.cpp:9:17: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘signed char&’
cin >> inp >> endl;
^~~~
In file included from /usr/include/c++/6/iostream:40:0,
from testlife.cpp:2:
/usr/include/c++/6/istream:803:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char*)
operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
^~~~~~~~
/usr/include/c++/6/istream:803:5: note: template argument deduction/substitution failed:
testlife.cpp:9:17: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘unsigned char*’
cin >> inp >> endl;
^~~~
In file included from /usr/include/c++/6/iostream:40:0,
from testlife.cpp:2:
/usr/include/c++/6/istream:808:5: note: candidate: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char*)
operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
^~~~~~~~
/usr/include/c++/6/istream:808:5: note: template argument deduction/substitution failed:
testlife.cpp:9:17: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘signed char*’
cin >> inp >> endl;
^~~~
In file included from /usr/include/c++/6/iostream:40:0,
from testlife.cpp:2:
/usr/include/c++/6/istream:924:5: note: candidate: template<class _CharT, class _Traits, class _Tp> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&&, _Tp&)
operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
^~~~~~~~
/usr/include/c++/6/istream:924:5: note: template argument deduction/substitution failed:
testlife.cpp:9:17: note: couldn't deduce template parameter ‘_Tp’
cin >> inp >> endl;
I have never encountered such error before nor I am unable to debug it given the simple block of code I am writing. I am using g++ compiler installed on ubuntu system.
Remove the endl from the cin statement:
cin >> inp;
Instead of:
cin >> inp >> endl;
There's no overload of the std::endl I/O manipulator for std::istream as the error message clearly states.
Also you should handle errors when taking input, otherwise your loop will run forever:
int main(){
while(true){
int inp;
if(cin >> inp && inp == 42) {
break;
}
else {
cin.clear();
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
continue;
}
cout << inp << endl;
}
return 0;
}
So I came on here earlier asking about a school assignment that involved reading each character from a file. That issue was fixed, but now I have encountered another problem.
Part of my assignment is to take in a user inputted file name, then set that file name to a text file that will be outputted with the results of the program.
Here is the program itself:
#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <fstream>
using namespace std;
int main()
{
const int fileNameSize = 20;
int fileCount = 0;
int testcount = 0;
const string outName;
std::ifstream inFile;
std::ofstream outFile;
<a bunch of other stuff>
outFile.open(outName);
int chartotal = acount + tcount + ecount + ocount + icount + ncount + scount + hcount + rcount;
outFile << "File name: " << inputFileName << endl;
outFile << "Number of E's: " << ecount << endl;
outFile << "Number of T's: " << tcount << endl;
outFile << "Number of A's: " << acount << endl;
outFile << "Number of O's: " << ocount << endl;
outFile << "Number of I's: " << icount << endl;
outFile << "Number of N's: " << ncount << endl;
outFile << "Number of S's: " << scount << endl;
outFile << "Number of H's: " << hcount << endl;
outFile << "Number of R's: " << rcount << endl;
outFile << "Total Number of Characters: " << chartotal << endl;
outFile << "--------------------------------" << endl;
outFile.close();
return 0;
}
inFile.close();
inFile.clear();
}
//cout << "exit colm flag";
//cout << "exit row flag\n";
}
It's my understanding that outFile.open(outName); should create a new file with the file name set as outName, however I just get a huge long error whenever I compile.
What am I doing wrong?
Edit: Here is the error I recieve
closed4Ahrens.cpp: In function 'int main()':
closed4Ahrens.cpp:19:9: error: no match for 'operator>>' in 'std::cin >> outName'
closed4Ahrens.cpp:19:9: note: candidates are:
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:122:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:122:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&) {aka std::basic_istream<char>& (*)(std::basic_istream<char>&)}'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:126:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>, std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:126:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:133:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:133:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'std::ios_base& (*)(std::ios_base&)'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:169:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:169:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'bool&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:173:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:173:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'short int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:176:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:176:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'short unsigned int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:180:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char, _Traits = std::char_traits<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:180:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:183:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:183:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'unsigned int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:187:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:187:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'long int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:191:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:191:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'long unsigned int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:196:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:196:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'long long int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:200:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:200:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'long long unsigned int&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:205:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:205:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'float&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:209:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:209:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'double&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:213:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:213:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'long double&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:217:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:217:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'void*&'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:241:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:241:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'std::basic_istream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}'
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/bits/basic_string.tcc:998:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::basic_string<_CharT, _Traits, _Alloc>&)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/bits/istream.tcc:957:5: note: template<class _CharT2, class _Traits2> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT2*)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/bits/istream.tcc:925:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:709:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char&)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:714:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char&)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:756:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char*)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/istream:761:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char*)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/iomanip:70:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Resetiosflags)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/iomanip:100:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setiosflags)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/iomanip:131:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setbase)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/iomanip:169:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setfill<_CharT>)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/iomanip:199:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setprecision)
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/iomanip:229:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::_Setw)
closed4Ahrens.cpp:68:24: error: no matching function for call to 'std::basic_ofstream<char>::open(const string&)'
closed4Ahrens.cpp:68:24: note: candidate is:
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/fstream:702:7: note: void std::basic_ofstream<_CharT, _Traits>::open(const char*, std::ios_base::openmode) [with _CharT = char, _Traits = std::char_traits<char>, std::ios_base::openmode = std::_Ios_Openmode]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/fstream:702:7: note: no known conversion for argument 1 from 'const string {aka const std::basic_string<char>}' to 'const char*'
Update: I deleted the const in const string outName, now the error message is much shorter
closed4Ahrens.cpp:68:24: error: no matching function for call to 'std::basic_ofstream<char>::open(std::string&)'
closed4Ahrens.cpp:68:24: note: candidate is:
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/fstream:702:7: note: void std::basic_ofstream<_CharT, _Traits>::open(const char*, std::ios_base::openmode) [with _CharT = char, _Traits = std::char_traits<char>, std::ios_base::openmode = std::_Ios_Openmode]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/fstream:702:7: note: no known conversion for argument 1 from 'std::string {aka std::basic_string<char>}' to 'const char*'
Update 2: I've done as Paul Evans suggested
string outFileName;
ifstream inFile;
ofstream outFile;
char inputFileName [fileNameSize+1];
cout << "How many files are being processed?\n";
cin >> fileCount;
cout << "What is the output file name?\n";
cin >> outFileName;
const string outName(outFileName);
and
outFile.open(outName);
And now I am receiving this error message:
closed4Ahrens.cpp: In function 'int main()':
closed4Ahrens.cpp:70:17: error: no matching function for call to 'std::basic_ofstream<char>::open()'
closed4Ahrens.cpp:70:17: note: candidate is:
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/fstream:702:7: note: void std::basic_ofstream<_CharT, _Traits>::open(const char*, std::ios_base::openmode) [with _CharT = char, _Traits = std::char_traits<char>, std::ios_base::openmode = std::_Ios_Openmode]
/opt/csw/lib/gcc/i386-pc-solaris2.10/4.6.3/../../../../include/c++/4.6.3/fstream:702:7: note: candidate expects 2 arguments, 0 provided
Your telling the compiler that outfile is const without initializing it, don't do that. Do this instead:
const string outName{"The path of the outfile"};
or
string outFileName;
// get outFileName
const string outName{outFileName};
I am attempting to print out the numbers from 1 to 1000 in C++ without any control statements or conditionals. I have found this question + answer on SO, but I cannot compile it on Linux with gcc 4.8. Any ideas why this is not working?
This is the code I'm trying:
#include <iostream>
template<int N>
struct NumberGeneration{
static void out(std::ostream& os)
{
NumberGeneration<N-1>::out(os);
os << N << std::endl;
}
};
template<>
struct NumberGeneration<1>{
static void out(std::ostream& os)
{
os << 1 << std::endl;
}
};
int main(){
NumberGeneration<1000>::out(std::cout);
}
The error I get is this:
main2.cpp:9:34: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) instantiating ‘struct NumberGeneration<100>’
NumberGeneration<N-1>::out(os);
^
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:9:34: error: incomplete type ‘NumberGeneration<100>’ used in nested name specifier
main2.cpp:10:8: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) substituting ‘template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char) [with _CharT = char; _Traits = std::char_traits<char>]’
os << N << std::endl;
^
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:10:8: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) substituting ‘template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, char) [with _Traits = std::char_traits<char>]’
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:10:8: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) substituting ‘template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, signed char) [with _Traits = std::char_traits<char>]’
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:10:8: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) substituting ‘template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, unsigned char) [with _Traits = std::char_traits<char>]’
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:10:13: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) substituting ‘template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, _CharT) [with _CharT = char; _Traits = std::char_traits<char>]’
os << N << std::endl;
^
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:10:13: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) substituting ‘template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>]’
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:10:13: error: template instantiation depth exceeds maximum of 900 (use -ftemplate-depth= to increase the maximum) substituting ‘template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::endl(std::basic_ostream<_CharT, _Traits>&) [with _CharT = char; _Traits = std::char_traits<char>]’
main2.cpp:9:34: recursively required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 999; std::ostream = std::basic_ostream<char>]’
main2.cpp:9:34: required from ‘static void NumberGeneration<N>::out(std::ostream&) [with int N = 1000; std::ostream = std::basic_ostream<char>]’
main2.cpp:21:28: required from here
main2.cpp:10:13: error: no match for ‘operator<<’ (operand types are ‘std::basic_ostream<char>’ and ‘<unresolved overloaded function type>’)
main2.cpp:10:13: note: candidates are:
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:108:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ostream_type& (*)(std::basic_ostream<_CharT, _Traits>::__ostream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(__ostream_type& (*__pf)(__ostream_type&))
^
/usr/include/c++/4.8/ostream:108:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_ostream<char>::__ostream_type& (*)(std::basic_ostream<char>::__ostream_type&) {aka std::basic_ostream<char>& (*)(std::basic_ostream<char>&)}’
/usr/include/c++/4.8/ostream:117:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ios_type& (*)(std::basic_ostream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>; std::basic_ostream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
operator<<(__ios_type& (*__pf)(__ios_type&))
^
/usr/include/c++/4.8/ostream:117:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_ostream<char>::__ios_type& (*)(std::basic_ostream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}’
/usr/include/c++/4.8/ostream:127:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(ios_base& (*__pf) (ios_base&))
^
/usr/include/c++/4.8/ostream:127:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::ios_base& (*)(std::ios_base&)’
/usr/include/c++/4.8/ostream:166:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(long __n)
^
/usr/include/c++/4.8/ostream:166:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long int’
/usr/include/c++/4.8/ostream:170:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(unsigned long __n)
^
/usr/include/c++/4.8/ostream:170:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long unsigned int’
/usr/include/c++/4.8/ostream:174:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(bool __n)
^
/usr/include/c++/4.8/ostream:174:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘bool’
In file included from /usr/include/c++/4.8/ostream:609:0,
from /usr/include/c++/4.8/iostream:39,
from main2.cpp:1:
/usr/include/c++/4.8/bits/ostream.tcc:91:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char; _Traits = std::char_traits<char>]
basic_ostream<_CharT, _Traits>::
^
/usr/include/c++/4.8/bits/ostream.tcc:91:5: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘short int’
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:181:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(unsigned short __n)
^
/usr/include/c++/4.8/ostream:181:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘short unsigned int’
In file included from /usr/include/c++/4.8/ostream:609:0,
from /usr/include/c++/4.8/iostream:39,
from main2.cpp:1:
/usr/include/c++/4.8/bits/ostream.tcc:105:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char; _Traits = std::char_traits<char>]
basic_ostream<_CharT, _Traits>::
^
/usr/include/c++/4.8/bits/ostream.tcc:105:5: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘int’
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:192:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(unsigned int __n)
^
/usr/include/c++/4.8/ostream:192:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘unsigned int’
/usr/include/c++/4.8/ostream:201:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(long long __n)
^
/usr/include/c++/4.8/ostream:201:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long long int’
/usr/include/c++/4.8/ostream:205:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(unsigned long long __n)
^
/usr/include/c++/4.8/ostream:205:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long long unsigned int’
/usr/include/c++/4.8/ostream:220:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(double __f)
^
/usr/include/c++/4.8/ostream:220:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘double’
/usr/include/c++/4.8/ostream:224:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(float __f)
^
/usr/include/c++/4.8/ostream:224:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘float’
/usr/include/c++/4.8/ostream:232:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(long double __f)
^
/usr/include/c++/4.8/ostream:232:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘long double’
/usr/include/c++/4.8/ostream:245:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
operator<<(const void* __p)
^
/usr/include/c++/4.8/ostream:245:7: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘const void*’
In file included from /usr/include/c++/4.8/ostream:609:0,
from /usr/include/c++/4.8/iostream:39,
from main2.cpp:1:
/usr/include/c++/4.8/bits/ostream.tcc:119:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_ostream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
basic_ostream<_CharT, _Traits>::
^
/usr/include/c++/4.8/bits/ostream.tcc:119:5: note: no known conversion for argument 1 from ‘<unresolved overloaded function type>’ to ‘std::basic_ostream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}’
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:548:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const unsigned char*)
operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
^
/usr/include/c++/4.8/ostream:548:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘const unsigned char*’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:543:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const signed char*)
operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
^
/usr/include/c++/4.8/ostream:543:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘const signed char*’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:530:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const char*)
operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
^
/usr/include/c++/4.8/ostream:530:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘const char*’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/ostream:609:0,
from /usr/include/c++/4.8/iostream:39,
from main2.cpp:1:
/usr/include/c++/4.8/bits/ostream.tcc:321:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const char*)
operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s)
^
/usr/include/c++/4.8/bits/ostream.tcc:321:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘const char*’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:513:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const _CharT*)
operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
^
/usr/include/c++/4.8/ostream:513:5: note: substitution of deduced template arguments resulted in errors seen above
/usr/include/c++/4.8/ostream:493:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, unsigned char)
operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
^
/usr/include/c++/4.8/ostream:493:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘unsigned char’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:488:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, signed char)
operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
^
/usr/include/c++/4.8/ostream:488:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘signed char’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:482:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, char)
operator<<(basic_ostream<char, _Traits>& __out, char __c)
^
/usr/include/c++/4.8/ostream:482:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘char’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:476:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char)
operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
^
/usr/include/c++/4.8/ostream:476:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: cannot convert ‘std::endl’ (type ‘<unresolved overloaded function type>’) to type ‘char’
os << N << std::endl;
^
In file included from /usr/include/c++/4.8/iostream:39:0,
from main2.cpp:1:
/usr/include/c++/4.8/ostream:471:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, _CharT)
operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
^
/usr/include/c++/4.8/ostream:471:5: note: substitution of deduced template arguments resulted in errors seen above
In file included from /usr/include/c++/4.8/string:52:0,
from /usr/include/c++/4.8/bits/locale_classes.h:40,
from /usr/include/c++/4.8/bits/ios_base.h:41,
from /usr/include/c++/4.8/ios:42,
from /usr/include/c++/4.8/ostream:38,
from /usr/include/c++/4.8/iostream:39,
from main2.cpp:1:
/usr/include/c++/4.8/bits/basic_string.h:2753:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
operator<<(basic_ostream<_CharT, _Traits>& __os,
^
/usr/include/c++/4.8/bits/basic_string.h:2753:5: note: template argument deduction/substitution failed:
main2.cpp:10:13: note: couldn't deduce template parameter ‘_Alloc’
os << N << std::endl;
^
And when I increase template instantiation depth I get :
$ gcc -Wall -ftemplate-depth=1100 -omain2 main2.cpp
/tmp/ccI81cmF.o: In function `main':
main2.cpp:(.text+0x5): undefined reference to `std::cout'
/tmp/ccI81cmF.o: In function `__static_initialization_and_destruction_0(int, int)':
main2.cpp:(.text+0x38): undefined reference to `std::ios_base::Init::Init()'
main2.cpp:(.text+0x47): undefined reference to `std::ios_base::Init::~Init()'
/tmp/ccI81cmF.o: In function `NumberGeneration<1>::out(std::ostream&)':
main2.cpp:(.text._ZN16NumberGenerationILi1EE3outERSo[_ZN16NumberGenerationILi1EE3outERSo]+0x19): undefined reference to `std::ostream::operator<<(int)'
main2.cpp:(.text._ZN16NumberGenerationILi1EE3outERSo[_ZN16NumberGenerationILi1EE3outERSo]+0x1e): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)'
main2.cpp:(.text._ZN16NumberGenerationILi1EE3outERSo[_ZN16NumberGenerationILi1EE3outERSo]+0x26): undefined reference to `std::ostream::operator<<(std::ostream& (*)(std::ostream&))'
/tmp/ccI81cmF.o: In function `NumberGeneration<1000>::out(std::ostream&)':
main2.cpp:(.text._ZN16NumberGenerationILi1000EE3outERSo[_ZN16NumberGenerationILi1000EE3outERSo]+0x25): undefined reference to `std::ostream::operator<<(int)'
main2.cpp:(.text._ZN16NumberGenerationILi1000EE3outERSo[_ZN16NumberGenerationILi1000EE3outERSo]+0x2a): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)'
main2.cpp:(.text._ZN16NumberGenerationILi1000EE3outERSo[_ZN16NumberGenerationILi1000EE3outERSo]+0x32): undefined reference to `std::ostream::operator<<(std::ostream& (*)(std::ostream&))'
As state in the comment, you reach the template depth limit, and use the wrong compiler:
so use a C++ compiler as g++
And then you may pass this argument to increase depth limit -depth=1000
or you may instantiate intermediate template as
template struct NumberGeneration<500>;
or rewrite your template to not use a depth linear with N
something like the following
// index_sequence and make_index_sequence available in C++14, but not in C++11
template <std::size_t...> struct index_sequence {};
namespace detail
{
template <typename, typename> struct concat;
template <std::size_t... Is1, std::size_t... Is2>
struct concat<index_sequence<Is1...>, index_sequence<Is2...>> :
index_sequence<Is1..., (sizeof...(Is1) + Is2)...>
{
using type = index_sequence<Is1..., (sizeof...(Is1) + Is2)...>;
};
}
template <std::size_t N>
struct make_index_sequence :
detail::concat<typename make_index_sequence<N / 2>::type,
typename make_index_sequence<N - N / 2>::type>::type
{
using type = typename
detail::concat<typename make_index_sequence<N / 2>::type,
typename make_index_sequence<N - N / 2>::type>::type;
};
template <>
struct make_index_sequence<1u> : index_sequence<0u> {
using type = index_sequence<0u>;
};
template <>
struct make_index_sequence<0u> : index_sequence<> {
using type = index_sequence<>;
};
And then with variadic template:
template<int N>
struct NumberGeneration{
static void out(std::ostream& os)
{
out(make_index_sequence<N>(), os);
}
private:
template<std::size_t ...Is>
static void out(index_sequence<Is...>, std::ostream& os)
{
std::initializer_list<int>{ ((os << (1 + Is) << std::endl), void(), 0)...};
}
};
Live example
The big problem is that it is really bad C++. It has a 1000 deep template instantiation depth, and the C++11 standard only advises 900. What more, there is little to no need for something that deep to do such a simple task.
Most compilers have template instantiation depth modification flags that make it larger. That is, however, a patch over the problem. The right way to fix that code is to either not write it, or decrease the depth.
#include <iostream>
template<int Max, unsigned Count=Max>
struct NumberGeneration{
void operator()(std::ostream& os) const
{
NumberGeneration<Max, (Count+1)/2>()(os);
NumberGeneration<Max-(Count+1)/2, (Count)/2>()(os);
}
};
template<int Max>
struct NumberGeneration<Max, 1>{
void operator()(std::ostream& os) const
{
os << Max << std::endl;
}
};
// not required:
template<int Max>
struct NumberGeneration<Max, 0>{
void operator()(std::ostream& os) const
{}
};
int main(){
NumberGeneration<1000>()(std::cout);
}
This now has a recursive template instantiation depth of about 10 instead of 1000, and is nearly as simple as the original version. I simply replaced single recursion with divide-and-conquer.
In C++14, efficient lists of integers via std::integral_sequence exist, and allow the above kind of thing even easier.
I also made NumberGeneration<X> into a stateless invokable type instead of having a static void out() method.
I have an enum in my code that is the following: enum Status {In-Active, Active};.
A status object is passed to a Person object as a parameter, so I want the user to enter Active or In-Active and save them in a Status variable. How can I do this? I tried it at first but it didnt work.
Here is my code:
#include <iostream>
using namespace std;
enum Status {InActive, Active};
class Person {
private:
string name;
int age;
Status status;
public:
Person (const string &_name, const int _age, const Status _status) : name(_name), age(_age), status(_status) {}
string &getName () { return name; }
int getAge () { return age; }
Status getStatus () { return status; }
void setName (const string &_name) { name = _name; }
void setAge (const int _age) { age = _age; }
void setStatus (const Status _status) { status = _status; }
};
////////////////////////////////////////////////////////////////////////////////
///////////////////////////////// Main Method //////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
int main () {
string name;
int age;
Status status;
cout << "Enter a name: "; getline(cin, name);
cout << "Enter age: "; cin >> age;
cout << "Enter status: "; cin >> status;
Person p(name, age, status);
return 0;
}
and here is the error I got (this is the build log):
Compiling: C:\Users\KiKo-SaMa\Desktop\C++\Person.cpp
C:\Users\KiKo-SaMa\Desktop\C++\Person.cpp: In function 'int main()':
C:\Users\KiKo-SaMa\Desktop\C++\Person.cpp:36:38: error: no match for 'operator>>' in 'std::cin >> status'
C:\Users\KiKo-SaMa\Desktop\C++\Person.cpp:36:38: note: candidates are:
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:122:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:122:7: note: no known conversion for argument 1 from 'Status' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&) {aka std::basic_istream<char>& (*)(std::basic_istream<char>&)}'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:126:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>, std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:126:7: note: no known conversion for argument 1 from 'Status' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:133:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:133:7: note: no known conversion for argument 1 from 'Status' to 'std::ios_base& (*)(std::ios_base&)'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:169:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:169:7: note: no known conversion for argument 1 from 'Status' to 'bool&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:173:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char, _Traits = std::char_traits<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:173:7: note: no known conversion for argument 1 from 'Status' to 'short int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:176:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:176:7: note: no known conversion for argument 1 from 'Status' to 'short unsigned int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:180:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char, _Traits = std::char_traits<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:180:7: note: no known conversion for argument 1 from 'Status' to 'int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:183:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:183:7: note: no known conversion for argument 1 from 'Status' to 'unsigned int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:187:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:187:7: note: no known conversion for argument 1 from 'Status' to 'long int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:191:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:191:7: note: no known conversion for argument 1 from 'Status' to 'long unsigned int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:196:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:196:7: note: no known conversion for argument 1 from 'Status' to 'long long int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:200:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:200:7: note: no known conversion for argument 1 from 'Status' to 'long long unsigned int&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:205:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:205:7: note: no known conversion for argument 1 from 'Status' to 'float&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:209:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:209:7: note: no known conversion for argument 1 from 'Status' to 'double&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:213:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:213:7: note: no known conversion for argument 1 from 'Status' to 'long double&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:217:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:217:7: note: no known conversion for argument 1 from 'Status' to 'void*&'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:241:7: note: std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:241:7: note: no known conversion for argument 1 from 'Status' to 'std::basic_istream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}'
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/basic_string.tcc:998:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::basic_string<_CharT, _Traits, _Alloc>&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/istream.tcc:957:5: note: template<class _CharT2, class _Traits2> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT2*)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/bits/istream.tcc:925:5: note: template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:709:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:714:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char&)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:756:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char*)
c:\mingw\bin\../lib/gcc/mingw32/4.6.2/include/c++/istream:761:5: note: template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char*)
Process terminated with status 1 (0 minutes, 0 seconds)
43 errors, 0 warnings
where did my code go wrong?
Thanks
You can't read enum values directly, you'll need a std::map that maps user input to an enum value.
std::map<std::string,Status> m;
m["In-Active"] = In-Active;
m["Active"] = Active;
std::string sstatus;
cin >> sstatus;
Status status = m[sstatus];
Enum objects are being parsed at compile time and it can only contain constant integer values.
Person p(name, age, status); //Here without using status object you should send a value directly like "In-Active" or "Active". So there would be no input from the user regarding th status field.
enum Status {InActive, Active};
Here Status is a enum class and any object created would contain values "Inactive" or "Active". If you try to assign some other value you would get an compiler error.
Status status;
Here status is an enum object created and it contains garbage value.
cout << "Enter status: "; cin >> status;
Here you are asking user for an input for an enum object which is totally invalid for the compiler.
You can also wrap the enum inside a class and provide operator>>. This is a modified example from this link http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Type_Safe_Enum
#include <iostream>
template<typename def>
class safe_enum : public def
{
public:
int val;
safe_enum(int v) : val(v) {}
// inner underlying() const { return val; }
bool operator == (const safe_enum & s) const { return this->val == s.val; }
bool operator != (const safe_enum & s) const { return this->val != s.val; }
bool operator < (const safe_enum & s) const { return this->val < s.val; }
bool operator <= (const safe_enum & s) const { return this->val <= s.val; }
bool operator > (const safe_enum & s) const { return this->val > s.val; }
bool operator >= (const safe_enum & s) const { return this->val >= s.val; }
};
struct status_def {
enum type { NoValue, InActive, Active };
};
typedef safe_enum<status_def> Status;
std::istream& operator>>(std::istream& Istr, Status& other)
{
std::cout << "Enter Status value: " << std::endl;
//here the logic to handle input error
Istr >> other.val;
return Istr;
}
std::ostream& operator<<(std::ostream& os,const Status& toPrint)
{
if (toPrint.val == Status::Active)
return os << "Active";
if (toPrint.val == Status::NoValue)
return os << "NoValue";
if (toPrint.val == Status::InActive)
return os << "InActive";
throw;
}
int main(void)
{
Status test(Status::NoValue);
std::cout << test << std::endl;
std::cin >> test;
std::cout << test << std::endl;
}