We have an atom with some keys and boolean values:
(def btns (reagent.core/atom {:a true :b true :c true}))
I need to change the state of all keys, like this: {:a false :b false :c false}
I tried this, but not good solution, and not working:
(for [btn #btns]
(swap! btns assoc (key btn) false))
you can update multiple keys this way:
user> (def a (atom {:a true :b true :c true}))
;;=> #<Atom#af0fa6a: {:a true, :b true, :c true}>
user> (swap! a into {:b false :c false})
;;=> {:a true, :b false, :c false}
or like this:
user> (swap! a assoc :a false :c false)
;;=> {:a false, :b true, :c false}
if you want to update all the keys in atom to false it could also look like this:
user> (reset! a (zipmap (keys #a) (repeat false)))
;;=> {:a false, :b false, :c false}
or like this:
user> (swap! a #(zipmap (keys %) (repeat false)))
;;=> {:a false, :b false, :c false}
update
also, it is good to abstract out the util function, to make it more readable:
(defn assoc-all-keys [data val]
(zipmap (keys data) (repeat val)))
user> (swap! a assoc-all-keys false)
;;=> {:a false, :b false, :c false}
Related
Suppose that I have a Clojure map like this:
(def mymap {:a [1 2 3] :b {:c [] :d [1 2 3]}})
I would like a function remove-empties that produces a new map in which entries from (:b mymap) that have an empty sequence as a value are removed. So (remove-empties mymap) would give the value:
{:a [1 2 3] :b {:d [1 2 3]}}
Is there a way to write a function to do this using Specter?
Here's how to do it with Specter:
(use 'com.rpl.specter)
(setval [:b MAP-VALS empty?] NONE my-map)
=> {:a [1 2 3], :b {:d [1 2 3]}}
In English, this says "Under :b, find all the map values that are empty?. Set them to NONE, i.e. remove them."
(update my-map :b (fn [b]
(apply dissoc b
(map key (filter (comp empty? val) b)))))
This is the specter solution:
(ns myns.core
(:require
[com.rpl.specter :as spc]))
(def my-map
{:a [1 2 3]
:b {:c []
:d [1 2 3]}})
(defn my-function
[path data]
(let [pred #(and (vector? %) (empty? %))]
(spc/setval [path spc/MAP-VALS pred] spc/NONE data)))
;; (my-function [:b] my-map) => {:a [1 2 3]
;; :b {:d [1 2 3]}}
I don't know specter either, but this is pretty simple to do in plain clojure.
(defn remove-empties [m]
(reduce-kv (fn [acc k v]
(cond (map? v) (let [new-v (remove-empties v)]
(if (seq new-v)
(assoc acc k new-v)
acc))
(empty? v) acc
:else (assoc acc k v)))
(empty m), m))
Caveat: For extremely nested data structures it might stack overflow.
So far I haven't found an approach with specter's filterer, because when I test filterers they seem to receive each map entry twice (once as a map entry and once as a 2-length vector) and giving different results between those seems to cause issues. However, we shouldn't be removing empty sequences anywhere they might appear, just map entries where they're the value.
I did seem to get a clojure.walk approach working that might still interest you, though.
(ns nested-remove
(:require [com.rpl.specter :as s]
[clojure.walk :refer [postwalk]]))
(defn empty-seq-entry? [entry]
(and (map-entry? entry) (sequential? (val entry)) (empty? (val entry))))
(defn remove-empties [root]
(postwalk #(if (map? %) (into (empty %) (remove empty-seq-entry? %)) %) root))
(remove-empties mymap) ;;=> {:a [1 2 3], :b {:d [1 2 3]}}
Assuming we only need to go one level deep and not search recursively like the accepted answer:
(setval [:b MAP-VALS empty?] NONE mymap)
A fully recursive solution that removes empty values in a map at any level
(def my-complex-map {:a [1] :b {:c [] :d [1 2 3] :e {:f "foo" :g []}}})
; declare recursive path that traverses map values
(declarepath DEEP-MAP-VALS)
(providepath DEEP-MAP-VALS (if-path map? [MAP-VALS DEEP-MAP-VALS] STAY))
(setval [DEEP-MAP-VALS empty?] NONE my-complex-map)
; => {:a [1], :b {:d [1 2 3, :e {:f "foo"}}}}
Reference the wiki on using specter recursively.
While I am not very familiar with Specter, in addition to the postwalk solution, you can solve this using tupelo.forest from the Tupelo library. You do need to rearrange the data a bit into Hiccup or Enlive format, then it's easy to identify any nodes with no child nodes:
(ns tst.clj.core
(:use clj.core tupelo.test)
(:require
[tupelo.core :as t]
[tupelo.forest :as tf] ))
(t/refer-tupelo)
(defn hid->enlive [hid]
(tf/hiccup->enlive (tf/hid->hiccup hid)))
(defn empty-kids?
[path]
(let [hid (last path)
result (and (tf/node-hid? hid)
(empty? (grab :kids (tf/hid->tree hid))))]
result))
; delete any nodes without children
(dotest
(tf/with-forest (tf/new-forest)
(let [e0 {:tag :root
:attrs {}
:content [{:tag :a
:attrs {}
:content [1 2 3]}
{:tag :b
:attrs {}
:content [{:tag :c
:attrs {}
:content []}
{:tag :d
:attrs {}
:content [1 2 3]}
]}]}
root-hid (tf/add-tree-enlive e0)
empty-paths (tf/find-paths-with root-hid [:** :*] empty-kids?)
empty-hids (mapv last empty-paths)]
(is= (hid->enlive root-hid) ; This is the original tree structure (Enlive format)
{:tag :root,
:attrs {},
:content
[{:tag :a,
:attrs {},
:content
[{:tag :tupelo.forest/raw, :attrs {}, :content [1]}
{:tag :tupelo.forest/raw, :attrs {}, :content [2]}
{:tag :tupelo.forest/raw, :attrs {}, :content [3]}]}
{:tag :b,
:attrs {},
:content
[{:tag :c, :attrs {}, :content []}
{:tag :d,
:attrs {},
:content
[{:tag :tupelo.forest/raw, :attrs {}, :content [1]}
{:tag :tupelo.forest/raw, :attrs {}, :content [2]}
{:tag :tupelo.forest/raw, :attrs {}, :content [3]}]}]}]})
(apply tf/remove-hid empty-hids) ; remove the nodes with no child nodes
(is= (hid->enlive root-hid) ; this is the result (Enlive format)
{:tag :root,
:attrs {},
:content
[{:tag :a,
:attrs {},
:content
[{:tag :tupelo.forest/raw, :attrs {}, :content [1]}
{:tag :tupelo.forest/raw, :attrs {}, :content [2]}
{:tag :tupelo.forest/raw, :attrs {}, :content [3]}]}
{:tag :b,
:attrs {},
:content
[{:tag :d,
:attrs {},
:content
[{:tag :tupelo.forest/raw, :attrs {}, :content [1]}
{:tag :tupelo.forest/raw, :attrs {}, :content [2]}
{:tag :tupelo.forest/raw, :attrs {}, :content [3]}]}]}]})
(is= (tf/hid->hiccup root-hid) ; same result in Hiccup format
[:root
[:a
[:tupelo.forest/raw 1]
[:tupelo.forest/raw 2]
[:tupelo.forest/raw 3]]
[:b
[:d
[:tupelo.forest/raw 1]
[:tupelo.forest/raw 2]
[:tupelo.forest/raw 3]]]])
)))
So I have this:
[{:a ["x" "y"], :b "foo"}
{:a ["x" "y" "z"], :b "bar"}]
And want this:
[{:a "x", :b "foo"}
{:a "y", :b "foo"}
{:a "x", :b "bar"}
{:a "y", :b "bar"}
{:a "z", :b "bar"}]
How can I do this?
for is really nice for known levels of nesting:
(for [x [{:a ["x" "y"], :b "foo"}
{:a ["x" "y" "z"], :b "bar"}]
a (:a x)]
(assoc x :a a))
You can use mapcat:
(def c [{:a ["x" "y"], :b "foo"}
{:a ["x" "y" "z"], :b "bar"}])
(mapcat (fn [{:keys [a] :as m}] (map #(assoc m :a %) a)) c)
I have an Atom, like x:
(def x (atom {:name "A"
:id 1
:children [{:name "B"
:id 2
:children []}
{:name "C"
:id 3
:children [{:name "D" :id 4 :children []}]}]}))
and need to update a submap like for example:
if :id is 2 , change :name to "Z"
resulting in an updated Atom:
{:name "A"
:id 1
:children [{:name "Z"
:id 2
:children []}
{:name "C"
:id 3
:children [{:name "D" :id 4 :children []}]}]}
how can this be done?
You could do it with postwalk or prewalk from the clojure.walk namespace.
(def x (atom {:name "A"
:id 1
:children [{:name "B"
:id 2
:children []}
{:name "C"
:id 3
:children [{:name "D" :id 4 :children []}]}]}))
(defn update-name [x]
(if (and (map? x) (= (:id x) 2))
(assoc x :name "Z")
x))
(swap! x (partial clojure.walk/postwalk update-name))
You could also use Zippers from the clojure.zip namespace
Find a working example here: https://gist.github.com/renegr/9493967
What's the idiomatic way of merging two lists of maps in Clojure where each map entry is identified by an id key?
What's an implementation for foo so that
(foo '({:id 1 :bar true :value 1}
{:id 2 :bar false :value 2}
{:id 3 :value 3})
'({:id 5 :value 5}
{:id 2 :value 2}
{:id 3 :value 3}
{:id 1 :value 1}
{:id 4 :value 4})) => '({:id 1 :bar true :value 1}
{:id 2 :bar false :value 2}
{:id 3 :value 3}
{:id 4 :value 4}
{:id 5 :value 5})
is true?
(defn merge-by
"Merges elems in seqs by joining them on return value of key-fn k.
Example: (merge-by :id [{:id 0 :name \"George\"}{:id 1 :name \"Bernie\"}]
[{:id 2 :name \"Lara\"}{:id 0 :name \"Ben\"}])
=> [{:id 0 :name \"Ben\"}{:id 1 :name \"Bernie\"}{:id 2 :name \"Lara\"}]"
[k & seqs]
(->> seqs
(map (partial group-by k))
(apply merge-with (comp vector
(partial apply merge)
concat))
vals
(map first)))
How about this:
(defn foo [& colls]
(map (fn [[_ equivalent-maps]] (apply merge equivalent-maps))
(group-by :id (sort-by :id (apply concat colls)))))
This is generalized so that you can have an arbitrary number of input sequences, and an arbitrary grouping selector:
(def a [{:id 5 :value 5}
{:id 2 :value 2}
{:id 3 :value 3}
{:id 1 :value 1}
{:id 4 :value 4}])
(def b [{:id 1 :bar true :value 1}
{:id 2 :bar false :value 2}
{:id 3 :value 3}])
(def c [{:id 1 :bar true :value 1}
{:id 2 :bar false :value 2}
{:id 3 :value 3}
{:id 4 :value 4}
{:id 5 :value 5}])
(defn merge-vectors
[selector & sequences]
(let [unpack-grouped (fn [group]
(into {} (map (fn [[k [v & _]]] [k v]) group)))
grouped (map (comp unpack-grouped (partial group-by selector))
sequences)
merged (apply merge-with merge grouped)]
(sort-by selector (vals merged))))
(defn tst
[]
(= c
(merge-vectors :id a b)))
I have two arrays of maps
1st is [{:a 1 :b 2 :d 6} {:a 2 :b 2} {:a 7 :b 7}]
2nd is [{:a 3 :c 3 :e 9 :y 7} {:a 2 :b 6 :c 8}]
depending on the value of a i.e. if its matches in 2nd array the '2nd map' should be merged with '1st map' and the resultant array of maps should be
Res should be [{:a 1 :b 2 :d 6} {:a 2 :b 6 :c 8} {:a 7 :b 7} {:a 3 :c 3 :e 9 :y 7}]
Can anyone help me on this. Thanks in advance.
Here you go:
user> (def xs [{:a 1 :b 2 :d 6} {:a 2 :b 2} {:a 7 :b 7}])
#'user/xs
user> (def ys [{:a 3 :c 3 :e 9 :y 7} {:a 2 :b 6 :c 8}])
#'user/ys
user> (for [[a ms] (group-by :a (concat xs ys))] (apply merge ms))
({:a 1, :b 2, :d 6} {:a 2, :c 8, :b 6} {:a 7, :b 7} {:y 7, :a 3, :c 3, :e 9})
This data structure looks very unwieldy to me nevertheless here's my take:
(defn key-by-a [coll]
"Convert a list of maps to a map of maps keyed by their vals at :a"
(apply hash-map (mapcat (juxt :a identity) coll)))
(defn merge-map-lists [l1 l2]
(->> [l1 l2]
(map key-by-a)
(apply merge-with merge)
(vals)))
One thing it doesn't do is maintaining order of the input lists but since it is not clear which list decides (both might have same keys in different orders) I left that out.
maybe clojure.set/join is what you want:
here is the docs of clojure.set/join:
user=> (def animals #{{:name "betsy" :owner "brian" :kind "cow"}
{:name "jake" :owner "brian" :kind "horse"}
{:name "josie" :owner "dawn" :kind "cow"}})
user=> (def personalities #{{:kind "cow" :personality "stoic"}
{:kind "horse" :personality "skittish"}})
#'user/personalities
user=> (join animals personalities)
#{{:owner "dawn", :name "josie", :kind "cow", :personality "stoic"}
{:owner "brian", :name "betsy", :kind "cow", :personality "stoic"}
{:owner "brian", :name "jake", :kind "horse", :personality "skittish"}}
user=> (join animals personalities)
#{{:kind "horse", :owner "brian", :name "jake", :species "cow", :personality "stoic"}
{:kind "cow", :owner "dawn", :name "josie", :species "cow", :personality "stoic"}
{:kind "horse", :owner "brian", :name "jake", :species "horse", :personality "skittish"}
{:kind "cow", :owner "brian", :name "betsy", :species "cow", :personality "stoic"}
{:kind "cow", :owner "dawn", :name "josie", :species "horse", :personality "skittish"}
{:kind "cow", :owner "brian", :name "betsy", :species "horse", :personality "skittish"}}
;; Notice that "Jake" is both a horse and a cow in the first line. That's
;; likely not what you want. You can tell `join` to only produce output
;; where the `:kind` value is the same as the `:species` value like this:
user=> (join animals personalities {:kind :species})
#{{:kind "cow", :owner "dawn", :name "josie", :species "cow", :personality "stoic"}
{:kind "horse", :owner "brian", :name "jake", :species "horse", :personality "skittish"}
{:kind "cow", :owner "brian", :name "betsy", :species "cow", :personality "stoic"}}