C ++ STL find () function does not accept custom class iterator arguments

Question

When I pass custom iterator arguments to std :: find (), GCC 5.2.1. the compiler (on Ubuntu 15.10) gives two error messages:

(1)

/usr/include/++/5/bits/stl_algo.h: 162: 34: error: no match function to call '__iterator_category (Text_iterator &)
standard :: __ iterator_category (__ first));

(2)

/usr/include/++/5/bits/stl_iterator_base_types.h: 204: 5: error: none type named 'iterator_category in' struct std :: iterator_traits

The error is caused by the line auto p = find(first, last, first_char);that is inside the find_txt () function. When a line is commented out, the code compiles easily. Here is a piece of code that causes errors:

#include "std_lib_facilities.h"//from B. Stroustrup site

using Line = vector<char>;

class Text_iterator {

    list<Line>::iterator ln; //points to lines
    Line::iterator pos; //points to characters

    public: 
    Text_iterator(list<Line>::iterator ll, Line::iterator pp)
        :ln{ll}, pos{pp} { }
    char& operator*() { return *pos; }
    Text_iterator& operator++();
    bool operator==(const Text_iterator& other) const
        { return ln==other.ln && pos==other.pos; }
    bool operator!=(const Text_iterator& other) const
        { return !(*this==other); }
};

Text_iterator& Text_iterator::operator++()
{
    ++pos;
    if (pos==(*ln).end()) {
    ++ln;
    pos = (*ln).begin();
}
    return *this;
}

Text_iterator find_txt(Text_iterator first, Text_iterator last, const string& s)
{
    if (s.size()==0) return last;// can’t find an empty stringchar first_char = s[0];
    char first_char = s[0];
    while (true) {
        auto p = find(first, last, first_char); //<------------the PROBLEM!!!!!!
        //if (p==last || match(p,last,s)) return p;
        //first = ++p;// look at the next character
    }
}

void ex6()
{
    ;
}


int main()
{
    ex6();
}

I mentioned the files mentioned in the error messages:

template<typename _Iterator, typename _Predicate>
    inline _Iterator
    __find_if(_Iterator __first, _Iterator __last, _Predicate __pred)
    {
        return __find_if(__first, __last, __pred,
        std::__iterator_category(__first)); //this is line #162 in stl_algo.h
    }

and

template<typename _Iter>
    inline typename iterator_traits<_Iter>::iterator_category
    __iterator_category(const _Iter&)//this is line #204 in stl_iterator_base_types.h
    { return typename iterator_traits<_Iter>::iterator_category(); }

auto p = find(first, last, first_char); GCC, stl_algo.h stl_iterator_base_types.h? ?

6, 20 " ": ++, 2- . . std:: find() . funtion.

Answer 1

( std::find) , Iterator. -

std::iterator_traits<It> typedefs value_type, difference_type, reference, pointer iterator_category

'iterator_category ' struct std:: iterator_traits

, , std::iterator_traits<Text_iterator>. , -, , .

: std::iterator_traits . , Iterator, InputIterator, std::find.

:

namespace std {
    template<>
    struct iterator_traits<Text_iterator> {
        typedef ptrdiff_t          difference_type;
        typedef char               value_type;
        typedef char*              pointer;
        typedef char&              reference;
        typedef input_iterator_tag iterator_category;
    };
}