Quiz response for: http://blog.adamcameron.me/2015/10/code-quiz-getting-next-three-elements.html

nextids.cfm

<cfscript>

array function nextIds(required array ids, required numeric id, numeric count = 0) {
    var idPos = arguments.ids.find(arguments.id);
    return arguments.ids.filter(function(item, index) {
        return idPos && index != idPos && index <= idPos + count;
    });
}

writeDump( nextIds([7141, 6881, 5821, 8001, 7904, 6601, 7961, 6021, 4721], 7141, 3) );
writeDump( nextIds([7141,6881,5821], 7141, 3) );
writeDump( nextIds([7141], 7141, 3) );
writeDump( nextIds([1111], 9999, 3) );

</cfscript>

nextids.clj

(defn next-ids
  [ids id count]
  (let [end-index (+ (.indexOf ids id) count)]
    (if (.contains ids id)
      (filterv (apply every-pred
        [#(not= % id) #(<= (.indexOf ids %) end-index)]) ids) [])))

(pprint (next-ids [7141 6881 5821 8001 7904 6601 7961 6021 4721] 7141 3))
(pprint (next-ids [7141 6881 5821] 7141 3))
(pprint (next-ids [7141] 7141 3))
(pprint (next-ids [1111] 9999 3))

nextids.groovy

List nextIds(List ids, int id, int count) {
    int endIndex = ids.indexOf(id) + count
    ids.findAll { id in ids && it != id && ids.indexOf(it) <= endIndex }
}

println nextIds([7141, 6881, 5821, 8001, 7904, 6601, 7961, 6021, 4721], 7141, 3).toString()
println nextIds([7141, 6881, 5821], 7141, 3).toString()
println nextIds([7141], 7141, 3).toString()
println nextIds([1111], 9999, 3).toString()

nextids.rb

def next_ids(ids, id, count)
    end_index = ids.index(id).nil? || ids.index(id) + count
    return ids.select { |item| (ids.include? id) && item != id && ids.index(item) <= end_index }
end

puts next_ids([7141, 6881, 5821, 8001, 7904, 6601, 7961, 6021, 4721], 7141, 3).inspect
puts next_ids([7141, 6881, 5821], 7141, 3).inspect
puts next_ids([7141], 7141, 3).inspect
puts next_ids([1111], 9999, 3).inspect

Updated the CFML to use index in filter() and tweaked the Groovy to be a bit simpler.

Tweaked the Clojure a bit. I have this feeling that the conditional is not necessary but I cannot get accurate results with what I've tried so far ;)

Added a Ruby example.