Expression for exploding "complex atomics" to maps

[ghislainfourny]

This is a counterproposal to the extension of the ? syntax to "complex atomics" such as dates.

The idea is that

Expr 🎆

explodes an atomic (like date, etc...) returned by Expr into a map (with fields year, month, etc).

(the choice of 🎆 is arbitrary and a placeholder for any other reasonable choice of syntax)

It can also work on a sequence of atomics, returning a sequence of maps.

Then one can write

(current-date():fireworks: )?year

where the semantics of ? is completely unchanged.

Parentheses are here for clarity on precedence, but may or may not be needed depending on the relative precedence of 🎆 and ?.

This way, 🎆 could be combined and used with all other functionality applying to maps (functions, obtaining the keys, the values, etc), providing a more general functionality than only for ?-based lookup.

As raised in Slack, it would be clear to anybody seeing 🎆 and getting an error with an XQuery 3.1 query that this is something new, rather than an existing ? with modified semantics

[ChristianGruen]

Hi Ghislain, a rather explosive proposal ;) So we could decide between 💥 and 🎆…

One (pretty boring) alternative would be a fn:to-map function, which binds the actual value to a value key and provide additional mappings depending on the type:

to-map(current-date())?year

[michaelhkay]

Yes, I did consider that approach. The downside is that it needs another magic symbol. An alternative would be a function map:from(current-date())?year but it doesn't read so nicely. Michael Kay Saxonica

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On 18 Dec 2020, at 16:02, Ghislain Fourny ***@***.***> wrote: This is a counterproposal to the extension of the ? syntax to "complex atomics" such as dates. The idea is that Expr 🎆 explodes an atomic (like date, etc...) returned by Expr into a map (with fields year, month, etc). (the choice of 🎆 is arbitrary and a placeholder for any other reasonable choice of syntax) It can also work on a sequence of atomics, returning a sequence of maps. Then one can write (current-date()🎆)?year where the semantics of ? is completely unchanged. Parentheses are here for clarity on precedence, but may or may not be needed depending on the relative precedence of 🎆 and ?. This way, 🎆 could be combined and used with all other functionality applying to maps (functions, obtaining the keys, the values, etc), providing a more general functionality than only for ?-based lookup. As raised in Slack, it would be clear to anybody seeing 🎆 and getting an error with an XQuery 3.1 that this is something new, rather than an existing ? with modified semantics — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#23>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AASIQISHEIBXZJWM6GFQET3SVN4IXANCNFSM4VBLTLMA>.

[michaelhkay]

I'm now inclined to have a function fn:parts() which extracts the components of an atomic value as a map, so you write parts(current-date())?year or current-date() => parts()?year It's a little bit harder this way to define the rules in such a way that implementations are allowed to raise an error statically if you do something inappropriate, like implicit-timezone() => parts?hour [should be "hours"], but I expect we can manage. Michael Kay Saxonica

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On 18 Dec 2020, at 16:18, Christian Grün ***@***.***> wrote: Hi Ghislain, a rather explosive proposal ;) So we could decide between 💥 and 🎆… One (pretty boring) alternative would be a fn:to-map function, which binds the actual value to a value key and provide additional mappings depending on the type: to-map(current-date())?year — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#23 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AASIQIVS5PWIY4EOZ7MS3K3SVN6FNANCNFSM4VBLTLMA>.

[ChristianGruen]

I’m in favor of the extra function. It seems better extensible to me as, in principle, the argument of an fn:parts function could also be a sequence, records, or function items (including maps and arrays).