function
boot.janet on line 1471, column 1
(update-in ds ks f & args)
Update a value in a nested data structure `ds`. Looks into `ds` via
a sequence of keys, and replaces the value found there with `f`
applied to that value. Missing data structures will be replaced
with tables. Returns the modified, original data structure.
(def ds @[@{:a 1 :b 2}
@{:a 8 :b 9}])
(defn thrice [x] (* x 3))
(update-in ds [0 :b] thrice)
# `ds` is now
@[@{:a 1 :b 6}
@{:a 8 :b 9}](defn ddup [ds ks val]
(update-in ds ks
(fn [x]
(if (= nil x)
@[val]
(array/push x val)))))
(var a @{})
(ddup a [:a] 1)
(ddup a [:a] 2)
(ddup a [:a] 3)
# @{:a @[1 2 3]}
(update-in @{:a @{:b 1}} [:a :b] (fn [x] (+ 1 x)))
# @{:a @{:b 2}}
(update-in @{:a 1} [:a] (fn [x] (+ 1 x)))
# @{:a 2}