example-or-fix-request: delimited-dsl where closing delimiter is also an escape leader

[dancingbug]

How to write a delimited-dsl closing delimiter that is the same as an escape leader?

suppose for sake of illustration that in the object language to be parsed, strings were delimited by %
Then I would want to match delimited strings as follows:

• "%one two%" --> "one two"
• "%one %% two%" --> "one % two"

In Pascal, for instance, the basic syntax of a string is delimited with single quotes.
If you want to escape a single quote inside such a string, you type it twice.

What is the recommended way to handle this?

here is a snippet that did not work

struct pct_quoted {
  static constexpr auto quote_sym = lexy::symbol_table<char>.map<'%'>('%');
  static constexpr auto rule = [] {
    auto delim = dsl::percent_sign;
    auto escape = dsl::escape(delim).symbol<quote_sym>();
    auto pct_q = dsl::delimited(delim, delim);
    return pct_q(dsl::ascii::character,escape);
  }();
};

void test_pct_quot() {
  auto input = lexy::zstring_input("%one%%two%");

  lexy::trace<pct_quoted>(stdout,input);
};

 1:  1: pct_quoted:
 1:  1: - literal: %
 1:  2: - token: one
 1:  5: - literal: %
 1:  6: - finish

Thank you for this nice library.

[foonathan]

A simple fix would be to change the closing delimiter to match % but not %% using dsl::not_followed_by: https://lexy.foonathan.net/playground/?id=xaazc4dMo&mode=tree.