Very nice! I like the readability-- not sure if thats just indicative of your style or the language, and the map construct is also nice. I don't remember any off-the-shelf map construct, at least not in Dyalog.
Dyalog doesn't have an explicit implementation for maps, but you get the same effect with column-major table stores and the implicit hashmap backing of the search-like primitives [0]. E.g.
keys←'foo' 'bar' 'baz'
values←1729 42 0.5721
indexOf←keys∘⍳ ⍝ The dyadic ⍳ here is what builds a hashmap
where ¯1 is just the value you want missing keys to map to. If you're okay erroring in that case, it can be left off. For map "literals", a syntax like the following gets you there for now:
k v ←'foo' 1729
k v⍪←'bar' 42
k v⍪←'baz' 0.5721
In version 20, proper array literal notation [1] is landing, where you'll be able to do:
keys values←↓⍉[
'foo' 1729
'bar' 42
'baz' 0.5721]
In practice, I suspect that this ends up being more ergonomic than actual maps would be in the language. That said K is all about maps and the entire language is designed around them instead of arrays like APL. IIRC, there was also some discussion on the J forums a while back about whether or not to have explicit hashmap support [2].
It's likely a combination of both. It's certainly possible to write Kap in a much more condensed form. But things like if-statements and hash maps does allow for a more imperative style.
