sp1r1t@pandora:~/eva$ g++ individuals.cpp main.cpp tree.cpp
individuals.h:20: error: ‘bool operator<(individual&)’ must take exactly two arguments
individuals.cpp:58: error: no ‘bool individual::operator<(individual&)’ member function declared in class ‘individual’
individuals.h:20: error: ‘bool operator<(individual&)’ must take exactly two arguments
/usr/lib/gcc/i486-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/list.tcc: In member function ‘void std::list<_Tp, _Alloc>::merge(std::list<_Tp, _Alloc>&) [with _Tp = individual, _Alloc = std::allocator<individual>]’:
/usr/lib/gcc/i486-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/list.tcc:257: instantiated from ‘void std::list<_Tp, _Alloc>::sort() [with _Tp = individual, _Alloc = std::allocator<individual>]’
main.cpp:48: instantiated from here
/usr/lib/gcc/i486-linux-gnu/4.1.2/../../../../include/c++/4.1.2/bits/list.tcc:222: error: no match for ‘operator<’ in ‘__first2. std::_List_iterator<_Tp>::operator* [with _Tp = individual]() < __first1. std::_List_iterator<_Tp>::operator* [with _Tp = individual]()’
individuals.h:20: note: candidates are: bool operator<(individual&)
individuals.h:20: error: ‘bool operator<(individual&)’ must take exactly two arguments