feat(arrays): add bisect(), bisectWith()

thi-ng · Dec 29, 2020 · 17d06a4 · 17d06a4
1 parent 971d5dc
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diff --git a/packages/arrays/src/bisect.ts b/packages/arrays/src/bisect.ts
@@ -0,0 +1,26 @@
+import type { Predicate } from "@thi.ng/api";
+
+/**
+ * Splits array at given index (default: floor(src.length/2)) and returns tuple of [lhs, rhs].
+ *
+ * @param src
+ * @param i
+ */
+export const bisect = <T>(src: T[], i = src.length >>> 1) => [
+    src.slice(0, i),
+    src.slice(i),
+];
+
+/**
+ * Similar to {@link bisect}, but first finds split index via provided
+ * predicate. The item for which the predicate first returns a truthy result,
+ * will be the first item in the RHS array. If the predicate never succeeds, the
+ * function returns `[src, []]`, i.e. all items will remain in the LHS.
+ *
+ * @param src
+ * @param pred
+ */
+export const bisectWith = <T>(src: T[], pred: Predicate<T>) => {
+    const i = src.findIndex(pred);
+    return i >= 0 ? bisect(src, i) : [src, []];
+};
diff --git a/packages/arrays/src/index.ts b/packages/arrays/src/index.ts
@@ -1,5 +1,6 @@
 export * from "./api";
 export * from "./binary-search";
+export * from "./bisect";
 export * from "./ends-with";
 export * from "./ensure-array";
 export * from "./ensure-iterable";