TIL that "tagged literals" have an existing meaning in clojure. In my mind,
the terms "tagged vector" and "tagged literal" were interchangeable. From a
quick Google search there doesn't seem to be an existing meaning for
"tagged vector". I think we can agree that it a representation of variants
in Clojure.
So given that, if we want to represent a single key/value pair, the
> most natural way to do it would be:
>
> [:foreground #color/rgb "ff0000"]
>
> Variants fulfil the same purpose as key/value pairs in a map. The key
> denotes a context-sensitive purpose for the data, rather than its type.
>
Could you elaborate on what you mean by variants being like a key value
pair? Also, for the purposes of discussing variants, we can ignore reader
tags right? I understand they serve a different purpose. The example in her
talk had the map
{:type :pickup :store-id 123
:address nil
:email nil}
and the equivalent variant was `[:pickup 123]`
If the map was instead
{:pickup {:store-id 123}
:digital nil
:delivery nil}
then yes, a variant could be thought of as a key value pair. Is this what
you meant?
On Sunday, 6 September 2015 13:29:05 UTC+5:30, James Reeves wrote:
>
> On 6 September 2015 at 02:31, Timothy Baldridge <tbald...@gmail.com
> <javascript:>> wrote:
>
>> >> Thanks, it helps to know using a tagged vector is a real pattern :)
>>
>> I don't know that it's a "real pattern". If I saw code like this in
>> production I would probably raise quite a stink about it during code
>> reviews. It's a cute hack, but it is also an abuse of a data structure. Now
>> when I see [:foo 42] I don't know if I have a vector of data or a tagged
>> value. It's a better idea IMO to use something like deftype or defrecord to
>> communicate the type of something. I'd much rather see #foo.bar.Age{:val
>> 42} than [:foo.bar/age 42]. At least then when I do (type val) I don't get
>> clojure.lang.PersistentVector.
>>
>
> I'll have to disagree with you here. To my mind, tagged literals don't
> quite have the same purpose as variants do.
>
> For example, consider a map:
>
> {:foreground #color/rgb "ff0000"
> :background #color/rgb "ffffff"}
>
> The hex strings are given a tag to indicate the type of data they contain,
> while the keys in the map tell us the purpose of that data.
>
> We clearly wouldn't write something like:
>
> #{#foreground {:val #color/rgb "ff0000"}
> #background {:val #color/rgb "ffffff"}}
>
> So given that, if we want to represent a single key/value pair, the most
> natural way to do it would be:
>
> [:foreground #color/rgb "ff0000"]
>
> Variants fulfil the same purpose as key/value pairs in a map. The key
> denotes a context-sensitive purpose for the data, rather than its type.
>
> - James
>
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