Найти самое короткое слово, встречающееся в предложении

#include <iostream>
#include <algorithm>
#include <iterator>
#include <string_view>
 
class words_iterator
{
public:
    using iterator_category = std::forward_iterator_tag;
    using value_type = std::string_view;
    using difference_type = std::ptrdiff_t;
    using pointer = std::string_view*;
    using reference = std::string_view&;
 
    words_iterator()
        : source_()
        , wsize_() 
    {}
 
    words_iterator(std::string_view source)
        : source_(source)
        , wsize_() 
    {
        to_next();
    }
 
    std::string_view operator*() const 
    {
        return source_.substr(0, wsize_); 
    }
 
    words_iterator& operator++() 
    {
        to_next();
        return *this;
    }
 
    words_iterator operator++(int) 
    {
        words_iterator result(*this);
        ++*this;
        return result;
    }
 
    bool operator==(const words_iterator& rhv) const 
    {
        return source_.empty() && rhv.source_.empty() 
            || (source_.data() == rhv.source_.data() && source_.size() == rhv.source_.size());
    }
 
    bool operator!=(const words_iterator& rhv) const 
    {
        return !(*this == rhv);
    }
 
private:
    void to_next()
    {
        auto predicate = [] (char ch) 
        {
            int uch = (int)(unsigned char)ch;
            return isalpha(uch) || isdigit(uch) || uch == '_';
        };
        const auto skipEnd = std::find_if(source_.begin() + wsize_, source_.end(), predicate);
        source_.remove_prefix(std::distance(source_.begin(), skipEnd));
        const auto wordEnd = std::find_if_not(source_.begin(), source_.end(), predicate);
        wsize_ = std::distance(source_.begin(), wordEnd);
    }
 
    std::string_view source_;
    size_t wsize_;
};
 
class words_sequence
{
public:
    words_sequence(std::string_view source)
        : source_(source) 
    {}
 
    words_iterator begin() const 
    { 
        return words_iterator(source_);
    }
 
    words_iterator end() const 
    { 
        return words_iterator(); 
    }
 
private:
    std::string_view source_;
};
 
 
int main()
{ 
    std::string_view source = "The class template basic_string_view describes an object that can refer to a constant contiguous sequence of char-like objects with the first element of the sequence at position zero.";
    words_sequence wseq(source);
    for (auto word: wseq)
        std::cout << "[" << word << "] ";
    std::cout << "\n";
    auto it = std::min_element(wseq.begin(), wseq.end(), [](std::string_view f, std::string_view s) { return f.size() < s.size(); });
    if (it != wseq.end())
        std::cout << "min: [" << *it << "]\n";
    else 
        std::cout << "no words found\n";
}