Undefined symbols for architecture i386:
  "operator/(decimal const&, decimal const&)", referenced from:
      custom_object::process(level&) in custom_object.o
      variant::operator/(variant const&) const in variant.o
  "operator<<(std::ostream&, decimal)", referenced from:
      TEST_sqrt_function() in formula_function.o
      variant::serialize_to_string(std::string&) const in variant.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)