Decorate-sort-undecorate idiom: Difference between revisions

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 =={{header|Kotlin}}==
-Kotlin already has a `sortedBy` function that can sort using a key extractor directly, so there is no need to decorate/undecorate. Nevertheless, the code example below shows how to decorate, sort and undecorate.
 <syntaxhighlight lang="kotlin">
 fun main() {
     val list = listOf("Rosetta", "Code", "is", "a", "programming", "chrestomathy", "site")
-    println(sorted(list, String::length))
+    println(list.sortedBySchwartzian(String::length))
 }
+/**
-fun <T, C: Comparable<C>> sorted(list: Collection<T>, keyFn: (T) -> C): List<T> =
+ * Returns a sorted list using the Schwartzian Transform which guarantees minimal use of the
-    list
+ * key extractor function. Use when the key extractor function is an expensive operation.
-        .map { it to keyFn(it) }
+*/
+fun <T, R: Comparable<R>> Collection<T>.sortedBySchwartzian(keyFn: (T) -> R): List<T> =
+    this.map { it to keyFn(it) }
         .sortedBy { it.second }
         .map { it.first }