On 6 September 2015 at 02:31, Timothy Baldridge <tbaldri...@gmail.com>
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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