Propose an Enumeration Type

[adamretter]

I have no idea right now how this would work or what it would look like! However, I have a feeling that the ability to define a sealed type of enumerations could be useful.

For example if I have a function like compute-checksum($algorithm, $data), it might be useful if I could define that the $algorithm is one of a number of enumerated (supported) values and nothing else.

A further example to start a discussion:

declare enumeration local:animal := {
    CAT
    DOG
    PIG
};

declare function local:sound($animal as enumeration(local:animal)) as xs:string {
    if ($animal eq local:animal:CAT) then
        "meow"
    else if ($animal eq local:animal:DOG) then
        "woof"
    else
        "oink"
};

[michaelhkay]

Enumeration types are great, but a new kind of type is a big addition to the language: it needs lots of infrastructure like subsumption rules etc. One way to handle this is like I tried to do with locally-defined union types: define it simply as a convenient way of defining an atomic type that is a restriction of xs:string with an enumeration facet, with the same semantics as if it was imported from a schema. Note that you would then be allowed to pass an enumeration to a function that expects a string, but not the other way around... Michael Kay Saxonica

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On 24 Nov 2018, at 03:27, Adam Retter ***@***.***> wrote: I have no idea right now how this would work or what it would look like! However, I have a feeling that the ability to define a sealed type of enumerations could be useful. For example if I have a function like compute-checksum($algorithm, $data), it might be useful if I could define that the $algorithm is one of a number of enumerated (supported) values and nothing else. A further example to start a discussion: declare enumeration local:animal := { CAT DOG PIG }; declare function local:sound($animal as local:animal) as xs:string { if ($animal eq local:animal:CAT) then "meow" else if ($animal eq local:animal:DOG) then "woof" else "oink" }; — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#17>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACSIIhad86WMSOBZTMc-qgfkbYKm4M8dks5uyLypgaJpZM4YxQN9>.