Raw strings starting/ending with backtick (original) (raw)

Cay Horstmann cay.horstmann at sjsu.edu
Mon Nov 26 09:44:50 UTC 2018

Le 26/11/2018 à 10:20, John Rose a écrit :

On Nov 26, 2018, at 1:05 AM, Cay Horstmann <cay.horstmann at sjsu.edu_ _<mailto:cay.horstmann at sjsu.edu>> wrote:

the scheme that I suggest would, in your notation be an OQ1 scheme, with Q = ''' and R = '\n', quoting any string s as n * Q + R + s + n * Q, with sufficiently large n. Do you recall what sharp edges one would run into? It's not intuitive to me and it would be good to learn from your experience. Having backtick-with-whitespace as an option besides backtick-alone basically introduces two new quoting conventions. Also, the choice of whitespace is tricky to use in syntax because whitespace displays ambiguously.  I'm sympathetic to using whitespace for R since it seems to make the two quoting conventions so similar that they are seemingly just one, with an optional tweak.  But the whitespace has downsides too: Making a quoting convention depend on details of whitespace is asking for puzzlers.  There are joke computer languages which depend on the distinction between O and 0, or space and tab; we don't want to be like that. 1. You'd want to use R ~ /\s*\n/ since there's no visual difference between that pattern and a simple /\n/.

Yes.

2. The close quote would have to contain R somewhere also, which leads to possible near-misses if the Q's are there and the R isn't.  Again, having R be next to invisible (whitespace) makes it harder to find a bug if it happens.

No, that was not what I intended. Any sequence m * Q, where m ≥ n, would close, with (m - n) * Q belonging to s.

I thought that was how it had to be. How else can you parse raw strings ending in backticks? But I just realized that is not how it works in 12-ea. I misunderstood how your closing quotes work. Would it be hard on the parser to do it my way?

3. After the R, you surely want the ability to strip some horizontal space also.

No.

We are adding an intrinsic "align" method to handle this.  My point is that mandating a newline causes new problems:  The user then is required to manage horizontal space on the new line.

I am aware of the "align" methods. Now those have sharp edges. Of course aligning problems can be avoided by placing the string at the leftmost column, like I have done in my example. This is why R = /\s*\n/ is a good choice.

4. The design of the close-quote has similar sharp edges.

Making R = '|' or some other printing character, and the close-quote be RQ*, would cause fewer problems with whitespace-related format.  But it would also in effect introduce a second quoting convention.

See above.

Cheers,

Cay

--

Cay S. Horstmann | http://horstmann.com | mailto:cay at horstmann.com

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