Maybe it is possible that removing lexer scanner? about ctpg HOT 2 OPEN

The problem is that the parser is supposed to be a constexpr object. This is the whole idea behind the library.

Now there are some problems:

• I need to calculate the size of a finite automaton table to construct a lexer, so...
• I need all of the sizes of regexes in compile time
• I would like to allow inline terms but only if they are expressed as literals, like say "[0-9]"_r

For the char_term and 'string_term' it is easy, for the regex term I found a way but in c++20 standard:

template<std::size_t N>
struct regex
{
    constexpr regex(const char (&str)[N])
    {
        std::ranges::copy(str, array);
    }

    char array[N];
};
 
template<regex a>
constexpr auto operator ""_r()
{
    return a;
}

int main()
{
    constexpr auto expr = "[0-9]"_r;
    return 0;
}

Of course I could allow inlining them like this: regex_term("[0-9]"), but this seemed to verbose and the grammar looked ugly.

from ctpg.

the target of inline is to solve the priority of matching lexer along with the process of syntax parsed. And i don't know whether or not it can realized and how to realize it. whereas the style of writing is not very important.

from ctpg.