title: Getting weird error when compiling
body: <pre><code>In file included from /usr/include/c++/7/bits/stl_algobase.h:71:0,  
                   from /usr/include/c++/7/bits/char_traits.h:39,  
                   from /usr/include/c++/7/ios:40,    
                   from /usr/include/c++/7/ostream:38,    
                   from /usr/include/c++/7/iostream:39,    
                   from /root/Desktop/proj08_main.cpp:2:  
  /usr/include/c++/7/bits/predefined_ops.h: In instantiation of ‘bool   __gnu_cxx::__ops::_Iter_pred&lt;_Predicate&gt;::operator()(_Iterator) [with _Iterator = __gnu_cxx::__normal_iterator&lt;std::__cxx11::basic_string&lt;char&gt;*, std::vector&lt;std::__cxx11::basic_string&lt;char&gt; &gt; &gt;; _Predicate = std::__cxx11::basic_string&lt;char&gt;]’:  
  /usr/include/c++/7/bits/stl_algo.h:120:14:   required from ‘_RandomAccessIterator std::__find_if(_RandomAccessIterator, _RandomAccessIterator, _Predicate, std::random_access_iterator_tag) [with _RandomAccessIterator =   __gnu_cxx::__normal_iterator&lt;std::__cxx11::basic_string&lt;char&gt;*, std::vector&lt;std::__cxx11::basic_string&lt;char&gt; &gt; &gt;; _Predicate = __gnu_cxx::__ops::_Iter_pred&lt;std::__cxx11::basic_string&lt;char&gt; &gt;]’
  /usr/include/c++/7/bits/stl_algo.h:161:23:   required from ‘_Iterator std::__find_if(_Iterator, _Iterator, _Predicate) [with _Iterator = __gnu_cxx::__normal_iterator&lt;std::__cxx11::basic_string&lt;char&gt;*, std::vector&lt;std::__cxx11::basic_string&lt;char&gt; &gt; &gt;; _Predicate = __gnu_cxx::__ops::_Iter_pred&lt;std::__cxx11::basic_string&lt;char&gt; &gt;]’  
  /usr/include/c++/7/bits/stl_algo.h:3932:28:   required from ‘_IIter std::find_if(_IIter, _IIter, _Predicate) [with _IIter = __gnu_cxx::__normal_iterator&lt;std::__cxx11::basic_string&lt;char&gt;*,   std::vector&lt;std::__cxx11::basic_string&lt;char&gt; &gt; &gt;; _Predicate = std::__cxx11::basic_string&lt;char&gt;]’  
  /usr/include/c++/7/bits/stl_algo.h:526:47:   required from ‘bool std::none_of(_IIter, _IIter, _Predicate) [with _IIter = __gnu_cxx::__normal_iterator&lt;std::__cxx11::basic_string&lt;char&gt;*, std::vector&lt;std::__cxx11::basic_string&lt;char&gt; &gt; &gt;; _Predicate = std::__cxx11::basic_string&lt;char&gt;]’  
  /root/Desktop/proj08_market.cpp:116:79:   required from here  
  /usr/include/c++/7/bits/predefined_ops.h:283:11: error: no match for call to ‘(std::__cxx11::basic_string&lt;char&gt;) (std::__cxx11::basic_string&lt;char&gt;&amp;)’
    { return bool(_M_pred(*__it)); }  
             ^~~~~~~~~~~~~~~~~~~~
  </code></pre>
  
  <p>I have checked every single line of my code and I have searched everywhere but I still can't find what causes this error.</p>