Re: Representation of strings and characters in XML version of ixml

There is still a problem regarding some characters that need escaping into the XML representation that I encountered in the grammar for XPath, e.g. the production for a value comparison, which uses ‘>=‘ which needs to be serialised as ‘<=‘., and similar cases with apostrophe and double quote. I’m not sure how that should be handled…

Forgive me, but I am a thousand miles away from code-full laptop so cannot get to the editable examples…..

John Lumley 

Sent from my iPad

> On 25 Dec 2021, at 16:38, C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com> wrote:
> 
> On 24,Dec2021, at 11:29 PM, Liam R. E. Quin <liam@fromoldbooks.org> wrote:
>> 
>>> On Fri, 2021-12-24 at 11:53 -0700, C. M. Sperberg-McQueen wrote:
>>> 
>>> That is, I like knowing, from whether something is a dstring
>>> or an sstring, … hmm.  I don’t know, from that, what I was
>>> about to say I knew. 
>> 
>> i've not been very active here (sorry) so maybe this is off kilter a
>> little - some languages/formats distinguish, though - e.g. in the Unix
>> shells, "$$" is the process ID of the current shell, and '$$" is two
>> dollar signs: interpolation happens in "..." and not in '...' so they
>> have to be treated differently.
>> 
>> But maybe that's not what's going on here?
>> 
> 
> Good point, but you are right that what is going on here is 
> different.  In ixml double and single quotes are used interchangeably;
> the only difference is that within single quotes, double quotes
> do not need to be escaped while single quotes do, and vice
> versa.
> 
> The only task affected by the decisions about whether the
> XML representation should preserve or lose the distinction between 
> single and double quotes in the ixml representation are, as far as
> I know, re-serializing the grammar from XML to ixml, or serializing
> in ixml a grammar first composed in XML.
> 
> If the distinctions are preserved, then when we re-serialize a
> grammar, the quotation marks will be unchanged, and when we
> serialize a born-XML grammar the grammar author can control
> whether the ixml grammar uses single or double quotes.
> 
> However, since we have agreed to suppress whitespace outside
> of literal strings and to lose the distinctions between ‘:’ and ‘=‘
> and between ‘;’ and ‘|’, re-serializing is not going to reproduce the
> original character stream in all cases.
> 
> The more I think about it, the more I think that preserving
> the distinction between dstring and sstring is just a relic of the
> time when the design wanted to preserve the accidentals of the
> ixml grammar, and is at best misleading.  So I now lean towards
> “let us mark them both as @string”.
> 
> Hex notation, on the other hand, I continue to regard as 
> something I’d like to preserve.
> 
> Michael
> 
>

Received on Saturday, 25 December 2021 17:33:05 UTC