/tmp/ccv0lOTL.o: In function `world_set(world_t&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >)':
simulation.cpp:(.text+0x38a9): undefined reference to `overlap_404(world_t&, int, int)'
simulation.cpp:(.text+0x40f6): undefined reference to `overlap_404(world_t&, int, int)'
collect2: error: ld returned 1 exit status