Finding all values of :b in the maps inside a vector inside a map inside a vector:
user=> (def x [{:a [{:b 1} {:b 2} {:a -30}]}
{}
{:a [{:b 3}]}])
user=> (select [ALL :a ALL :b] x)
[1 2 nil 3]Replacing vectors of numbers with their sums:
user=> (def x [{:a [1 2 3]}
{:a [3 4 5]}])
user=> (transform [ALL :a] (partial apply +) x)
[{:a 6} {:a 12}]Summing vectors, but leaving lists of numbers alone:
user=> (def x [{:a [1 2 3]}
{:a '(-40 -45)}
{:a [4 5 6]}])
user=> (transform [ALL :a vector?] (partial apply +) x)
[{:a 6} {:a (-40 -45)} {:a 15}]Extracting all the vectors from a tree, regardless of nesting level:
user=> (def x `(list [1 2 3]
(concat [4 5 6] [7 8 9])))
user=> (select (walker vector?) x)
([1 2 3] [4 5 6] [7 8 9])Reversing the first two elements of any vector, ignoring other types:
user=> (def x (vector "not vector"
["first" "SECOND" 3 4]
"not vector"
[-11111 2] ])
user=> (transform [ALL vector? (srange 0 2)] reverse x)
["not vector" ["SECOND" "first" 3 4] "not vector" [2 -11111]]Showing the even values of vectors along with their indices:
user=> (defn describe-evens [v]
(->> v
(select [(view (partial map-indexed vector))
ALL
(collect-one FIRST)
LAST
even?])
(map (fn [[index val]]
(format "index %d has value %d" index val)))))
user=> (describe-evens [-1 -2 -3 -4])
("index 1 has value -2" "index 3 has value -4")