Why this template recursion won't compile? - c++

Question

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&))'

Answer 1

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

Answer 2

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.