On Apr 29, 2019, at 8:48 AM, Guy Steele <guy.ste...@oracle.com> wrote: > >> On Apr 28, 2019, at 4:32 PM, Brian Goetz <brian.go...@oracle.com> wrote: >> >> . . . >> Looking ahead to the next round, we can build on this. In the first round, >> we mistakenly thought that there was something that could reasonably be >> called a “raw” string, but this notion is a fantasy; no string literal is so >> raw that it can’t recognize its closing delimiter. So “rawness” is really >> only a matter of degree. > > This is _almost_ true. If a string is truly raw (that is, it can contain > _anything_), then one absolutely cannot depend on recognizing the closing > delimiter by examining what might be the raw content. > > Put another way: one cannot determine how long the raw content is by > examining it. That’s a solid principle.
I'm going to be nit-picky here and refer to my earlier mentions of the paradigm of strong quoting, which at its heart simply means you have an infinite set of delimiters to choose from, when wrapping a payload into a literal syntax. Adding a numeral to the open quote means that there are now an unbounded set of open quotes, so it is an instance of strong quoting. Another instance of strong quoting adds nonces, and yet another just lengthens the quote pattern until it doesn't occur (anywhere) in the raw string payload. The numeric prefix convention is different from other kinds of strong quoting conventions, in that the end-quote can be a substring of the payload. Actually, the end-quote is most naturally the empty string, which is a substring of every string. The numeric prefix convention and other strong-quote conventions all share a common property: The convention as a whole is universal for arbitrary payloads, but for any given payload there are quotes which work and others that don't work. In the case of the numeric prefix convention, once you choose an open-quote (with numeral) you are limited to payloads of that length. That's not quite a "raw string" any more, since it's suitable only for a fixed-sized character field. Likewise, once you choose a particular nonce-based or patterned quote (e.g., seven double-quotes), payloads containing the corresponding end-quote as a substring are no longer suitable. Once you pick a particular payload string, the next question is whether you can embed that particular string into your program without inserting escape sequences. Only with a strong quote scheme of some sort is this possible. But, with any of several strong quote schemes, it is possible to dispense with escapes for any given string; it is not a fantasy. — John
