clojure.core/sort-by

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Type: function Added: Clojure 1.0 Examples: 13 Runnable: 5

([keyfn coll] [keyfn comp coll])

Returns a sorted sequence of the items in coll, where the sort order is determined by comparing (keyfn item). If no comparator is supplied, uses compare. comparator must implement java.util.Comparator. Guaranteed to be stable: equal elements will not be reordered. If coll is a Java array, it will be modified. To avoid this, sort a copy of the array.

Examples

by zmila on 2010-08-11 . May have evaluation errors. ▶

(sort-by count ["aaa" "bb" "c"]) ("c" "bb" "aaa") (sort-by first [[1 2] [2 2] [2 3]]) ([1 2] [2 2] [2 3]) (sort-by first > [[1 2] [2 2] [2 3]]) ([2 2] [2 3] [1 2])

by kotarak on 2010-08-11 ▶

(sort-by :rank [{:rank 2} {:rank 3} {:rank 1}]) ({:rank 1} {:rank 2} {:rank 3})

by shuaybi on 2011-05-14 ▶

(def x [{:foo 2 :bar 11} {:bar 99 :foo 1} {:bar 55 :foo 2} {:foo 1 :bar 77}]) ;sort by :foo, and where :foo is equal, sort by :bar (sort-by (juxt :foo :bar) x) ;=>({:foo 1, :bar 77} {:bar 99, :foo 1} {:foo 2, :bar 11} {:bar 55, :foo 2})

by jamesqiu on 2011-08-16 . May have evaluation errors. ▶

(def x [{:foo 2 :bar 11} {:bar 99 :foo 1} {:bar 55 :foo 2} {:foo 1 :bar 77}]) ; sort-by given key order (:bar) (def order [55 77 99 11]) (sort-by #((into {} (map-indexed (fn [i e] [e i]) order)) (:bar %)) x) ;=> ({:bar 55, :foo 2} {:foo 1, :bar 77} {:bar 99, :foo 1} {:foo 2, :bar 11})

by Yogthos on 2012-01-28 . May have evaluation errors. ▶

;sort entries in a map by value (sort-by val > {:foo 7, :bar 3, :baz 5}) ([:foo 7] [:baz 5] [:bar 3])

by jafingerhut on 2012-03-15 . May have evaluation errors. ▶

;; Warning: You can sort a Java array and get back a sorted immutable Clojure ;; data structure, but it will also change the input Java array, by sorting it. ;; Copy the array before sorting if you want to avoid this. (def x (to-array [32 -5 4 11])) #'user/x (seq x) (32 -5 4 11) (def y (sort-by - x)) #'user/y ;; Return sorted sequence y (32 11 4 -5) ;; but also modifies x, because it used the array to do the sorting. (seq x) (32 11 4 -5) ;; One way to avoid this is copying the array before sorting: (def y (sort-by - (aclone x))) #'user/y

by foxlog on 2015-04-22 . May have evaluation errors. ▶

;;; from the joy of clojure 2nd ;;; function as arguments (def plays [{:band "Burial", :plays 979, :loved 9} {:band "Eno", :plays 2333, :loved 15} {:band "Bill Evans", :plays 979, :loved 9} {:band "Magma", :plays 2665, :loved 31}]) (def sort-by-loved-ratio (partial sort-by #(/ (:plays %) (:loved %)))) (sort-by-loved-ratio plays) ;=> ({:band "Magma", :plays 2665, :loved 31} {:band "Burial", :plays 979, :loved 9} {:band "Bill Evans", :plays 979, :loved 9} {:band "Eno", :plays 2333, :loved 15}) ;;; others. (sort-by second [[:a 7], [:c 13], [:b 21]]) ;;=> ([:a 7] [:c 13] [:b 21]) (sort-by str ["z" "x" "a" "aa" 1 5 8]) ;;=> (1 5 8 "a" "aa" "x" "z") (sort-by :age [{:age 99}, {:age 13}, {:age 7}]) ;;=> ({:age 7} {:age 13} {:age 99})

by egracer on 2016-08-12 . May have evaluation errors. ▶

;; you can pass a comparator to specify the order to sort in ;; typical sort, low to high (sort-by :value [{:value 1 :label "a"} {:value 3 :label "c"} {:value 2 :label "b"}]) ;=> ({:value 1, :label "a"} {:value 2, :label "b"} {:value 3, :label "c"}) ;; override the default comparator to sort high to low (sort-by :value #(> %1 %2) [{:value 1 :label "a"} {:value 3 :label "c"} {:value 2 :label "b"}]) ;=> ({:value 3 :label "c"} {:value 2, :label "b"} {:value 1, :label "a"}) ;; sort-by behavior when :value is absent (sort-by :value [{:value 1 :label "a"} {:label "c"} {:value 2 :label "b"}]) => ({:label "c"} {:value 1, :label "a"} {:value 2, :label "b"}) ;; now if you provide custom comparator when :value is absent you will get NullPointerException (sort-by :value #(> %1 %2) [{:value 1 :label "a"} {:label "c"} {:value 2 :label "b"}]) => Execution error (NullPointerException) at user/eval1515$fn (form-init71750676547201835.clj:1). null ;; make above working by simple or; considering absence of "value" as invaluable or highest value :) (sort-by :value #(> (or %1 Integer/MAX_VALUE) (or %2 Integer/MAX_VALUE)) [{:value 1 :label "a"} {:label "c"} {:value 2 :label "b"}]) => ({:label "c"} {:value 2, :label "b"} {:value 1, :label "a"})

by overset on 2017-03-03 ▶

;; to sort by nested hash-map values ;; with the help of get-in and custom comparator (sort-by #(get-in (val %) [:price]) {:chair {:price 10} :table {:price 9} :lamp {:price 9}}) ;;=> ([:table {:price 9}] [:lamp {:price 9}] [:chair {:price 10}])

by fdhenard on 2019-05-09 ▶

;; sort-by descending (reverse) (sort-by :rank #(compare %2 %1) [{:rank 2} {:rank 3} {:rank 1}]) ({:rank 3} {:rank 2} {:rank 1})

by cgaustin on 2020-10-08 . May have evaluation errors. ▶

;; Warning: sort-by will not apply the keyfn on coll's of length 1 (sort-by (fn [i] (nth i) 4) [[1 2 3]]) ([1 2 3]) (nth [1 2 3] 4) ; IndexOutOfBoundsException clojure.lang.PersistentVector.arrayFor (PersistentVector.java:158)...

by naxels on 2021-05-30 ▶

;; Using comp as a way to sort descending (def unordered '({:created_at 1612637437} {:created_at 1610998684} {:created_at 1622245799})) (sort-by (comp - :created_at) unordered) ;;=> ({:created_at 1622245799} {:created_at 1612637437} {:created_at 1610998684}) ;; Note: using the negative - as a comparator won't work ;; so you need to combine the functions ;; same example without comp: (sort-by #(- (:created_at %)) unordered) ;;=> ({:created_at 1622245799} {:created_at 1612637437} {:created_at 1610998684})

by arcanjoaq on 2025-03-31 . May have evaluation errors. ▶

;; Using a comparator to compare LocalDateTime (def to-be-sorted [{:time (java.time.LocalDateTime/parse "2025-01-29T11:26:00")} {:time (java.time.LocalDateTime/parse "2025-01-29T11:27:00")} {:time (java.time.LocalDateTime/parse "2025-01-29T11:23:00")}]) ;; sort asc (sort-by :time to-be-sorted) ;; sort desc (sort-by :time #(.compareTo %2 %1) to-be-sorted)

See also

• clojure.core/sort (1)
• clojure.core/compare (3)

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