#include <string>

class Sentence
{
public:

    Sentence(std::string const& input)
        : data {input}
    {
        if( words() < 1)
        {
            throw std::logic_error{"För kort mening!"};
        }
        if( words() > 9 )
        {
            throw std::logic_error{"För lång mening!"};
        }
    }

    void add_word(std::string const& new_word)
    {
        if (words() >= 9)
        {
            throw std::logic_error{"Redan maximal längd för meningen!"};
        }
        
        data += " ";
        data += new_word;
    }

private:
    std::string data;

    int words() const
    {
        int spaces {};
        for(char l : data)
        {
            if (l == ' ')
            {
                ++spaces;
            }
        }
        return spaces + 1;
    }
};

Sentence operator+(std::string const& new_word, Sentence const& sentence)
{
    Sentence new_sentence {sentence};
    new_sentence.add_word(new_word);
    return new_sentence;
}