From d517c8736ddaccfb85e1c00b347eadec81dd1310 Mon Sep 17 00:00:00 2001
From: David Sehnal <david.sehnal@gmail.com>
Date: Thu, 9 Nov 2017 16:54:31 +0100
Subject: [PATCH] added data/util/group-by
---
src/mol-data/util/grouping.ts | 47 +++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)
create mode 100644 src/mol-data/util/grouping.ts
diff --git a/src/mol-data/util/grouping.ts b/src/mol-data/util/grouping.ts
new file mode 100644
index 000000000..213f3cf54
--- /dev/null
+++ b/src/mol-data/util/grouping.ts
@@ -0,0 +1,47 @@
+/**
+ * Copyright (c) 2017 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author David Sehnal <david.sehnal@gmail.com>
+ */
+
+export interface Grouping<V, K> {
+ keys: ReadonlyArray<K>,
+ groups: ReadonlyArray<ReadonlyArray<V>>
+}
+
+class GroupingImpl<K, V> {
+ private byKey = new Map<K, V[]>();
+ readonly keys: K[] = [];
+ readonly groups: V[][] = [];
+
+ add(a: V) {
+ const key = this.getKey(a) as any;
+ if (!!this.byKey.has(key)) {
+ const group = this.byKey.get(key)!;
+ group[group.length] = a;
+ } else {
+ const group = [a];
+ this.byKey.set(key, group);
+ this.keys[this.keys.length] = key;
+ this.groups[this.groups.length] = group;
+ }
+ }
+
+ getGrouping(): Grouping<V, K> {
+ return { keys: this.keys, groups: this.groups };
+ }
+
+ constructor(private getKey: (v: V) => K) { }
+}
+
+export function Grouper<V, K>(getKey: (x: V) => K) {
+ return new GroupingImpl<K, V>(getKey);
+}
+
+function groupBy<V, K>(values: ArrayLike<V>, getKey: (x: V) => K) {
+ const gs = Grouper(getKey);
+ for (let i = 0, _i = values.length; i < _i; i++) gs.add(values[i]);
+ return gs.getGrouping();
+}
+
+export default groupBy;
\ No newline at end of file
--
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