Re: Thoughts on pragmas and iXML

On Fri, Feb 14, 2025 at 01:40:21AM +0000, Bethan Tovey-Walsh scripsit:
>> Which makes me think there will need to be some requirement to
>> resolve the meaning of overlapping scope
> 
> Right, I see. (I say that with the same inevitable caveat as before.)

Talking about the requirements of an already abstract unnatural grammar
does not come naturally to anyone, at least not so far as I've observed.

Communication is observed to occur; I think this is success.

> I still believe that this must be managed by the semantics of the
> pragma. 

What the processor does, yes, that goes into the semantics of the
pragma, is implementation-specific, and up to the implementer. 

I would contend that the syntax of pragmas, on the other hand, needs to
allow someone reading a grammar to know which pragmas pertain to which
grammar constructs. It should be possible to know by inspection which
pragmas pertain to a construct even while it should NOT be possible to
know what they're going to do.

As a user, if I am reading a grammar which contains pragmas and I see
something that could be abstracted as

pragma{A} pragma{A} pragma{B} LHS = RHS

how do I read it?

I ought to have a pretty good idea that all three instances of pragmas
apply to that left hand side. But if absolutely everything is up to the
implementer, I then have to figure out which processor version I'm using
and go read some documentation; is this an implementation which applies
the last associated pragma? the first? is it going to throw an error?
how many times is pragma A going to be applied? A user should not, by
design, be that confused; they should be able to learn some few simple
rules about the pragma part of speech and be able to apply those during
inspection.

[snip]
> On a more practical level, it's much easier to have a requirement that
> pragma-data (and thus semantics) are not part of the specification,
> than to say "pragma semantics  should usually be down to the
> implementer, except in these four cases..." Slippery slopes, and all
> that. 

Don't want to specify the semantics; do want sufficiently specific
syntax that I can tell by inspection (for some "in principle" value of
inspection if necessary) what pragmas pertain to what grammar
constructs.
 
>> I think an analogy from natural language may apply; one may not know
>> what the word means, but one would still know where to put it in a
>> sentence if one knew what part of speech it was. 
> 
> Ooh, I like this. What are slithy toves? Who knows! But "slithy" is an
> adjective and "toves" is a plural noun, and you can therefore have "a
> slithy tove", and make it the subject of a verb if you feel like it. 

To extend this a bit; the user also needs to know something about the
rules for multiple adjectives; can the tove be slithy AND mimsy at one
time? is a slithy slithy tove more slithy than a slithy tove, not slithy
(because the sentence must stop for repairs), or only so slithy as a
tove declared slithy once?

Much appreciated,
Graydon


--  
Graydon Saunders  | graydonish@fastmail.com
Þæs oferéode, ðisses swá mæg.
-- Deor  ("That passed, so may this.")

Received on Friday, 14 February 2025 16:25:46 UTC