Error(s):

C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\type_traits(1441): error C2672: 'std::invoke': no matching overloaded function found
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(208): note: see reference to function template instantiation '_Rx std::_Invoke_ret<_Rx,_Callable&,_Ty,_Ty>(std::_Forced<_Rx,false>,_Callable &,_Ty &&,_Ty &&)' being compiled
        with
        [
            _Rx=int,
            _Callable=_Decayed,
            _Ty=Fraction
        ]
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(206): note: while compiling class template member function 'int std::_Func_impl<_Decayed,_Alloc,_Ret,Fraction,Fraction>::_Do_call(Fraction &&,Fraction &&)'
        with
        [
            _Alloc=std::allocator<int>,
            _Ret=int
        ]
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(134): note: see reference to class template instantiation 'std::_Func_impl<_Decayed,_Alloc,_Ret,Fraction,Fraction>' being compiled
        with
        [
            _Alloc=std::allocator<int>,
            _Ret=int
        ]
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(337): note: see reference to class template instantiation 'std::_Is_large<_Myimpl>' being compiled
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(316): note: see reference to function template instantiation 'void std::_Func_class<_Ret,Fraction,Fraction>::_Reset_alloc<_Ty,std::allocator<int>>(_Fx &&,const _Alloc &)' being compiled
        with
        [
            _Ret=int,
            _Ty=Comparator,
            _Fx=Comparator,
            _Alloc=std::allocator<int>
        ]
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(316): note: see reference to function template instantiation 'void std::_Func_class<_Ret,Fraction,Fraction>::_Reset_alloc<_Ty,std::allocator<int>>(_Fx &&,const _Alloc &)' being compiled
        with
        [
            _Ret=int,
            _Ty=Comparator,
            _Fx=Comparator,
            _Alloc=std::allocator<int>
        ]
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(482): note: see reference to function template instantiation 'void std::_Func_class<_Ret,Fraction,Fraction>::_Reset<Comparator>(_Fx &&)' being compiled
        with
        [
            _Ret=int,
            _Fx=Comparator
        ]
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\functional(482): note: see reference to function template instantiation 'void std::_Func_class<_Ret,Fraction,Fraction>::_Reset<Comparator>(_Fx &&)' being compiled
        with
        [
            _Ret=int,
            _Fx=Comparator
        ]
source_file.cpp(18): note: see reference to function template instantiation 'std::function<int (Fraction,Fraction)>::function<Comparator>(_Fx)' being compiled
        with
        [
            _Fx=Comparator
        ]
source_file.cpp(18): note: see reference to function template instantiation 'std::function<int (Fraction,Fraction)>::function<Comparator>(_Fx)' being compiled
        with
        [
            _Fx=Comparator
        ]
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\type_traits(1441): error C2893: Failed to specialize function template 'unknown-type std::invoke(_Callable &&,_Types &&...)'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\type_traits(1441): note: With the following template arguments:
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\type_traits(1441): note: '_Callable=_Decayed &'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\type_traits(1441): note: '_Types={Fraction, Fraction}'
Microsoft (R) C/C++ Optimizing Compiler Version 19.00.23506 for x64