feat: Add function repeatFn()

Author: koraa

src/sequence.js

@@ -215,13 +215,30 @@ function* range(start, end) {
  */
 const range0 = b => range(0, b);
 
-/** Generates an infinite iterator of the given value. */
-function* repeat(val) {
+/**
+ * Generates an infinite iterator by invoking the
+ * given function repeatedly.
+ *
+ * @function
+ * @param {Function} fn
+ * @returns {Sequence}
+ */
+function* repeatFn(fn) {
   while (true) {
-    yield val;
+    yield fn();
   }
 }
 
+/**
+ * Generates an infinite iterator of the given value.
+ *
+ * @function
+ * @template T
+ * @param {T} val
+ * @returns {Sequence<T>}
+ */
+const repeat = val => repeatFn(() => val);
+
 /**
  * Generate a sequence by repeatedly calling the same function on the
  * previous value.
@@ -1616,6 +1633,7 @@ module.exports = {
   iter,
   range,
   range0,
+  repeatFn,
   repeat,
   extend,
   extend1,

test/sequence.test.js

@@ -17,7 +17,7 @@ const assert = require('assert');
 const {
   and, plus, or, mul, not,
   size, TraitNotImplemented, _typedArrays,
-  iter, range, range0, repeat, extend, extend1, flattenTree,
+  iter, range, range0, repeat, repeatFn, extend, extend1, flattenTree,
   IteratorEnded, next, tryNext, nth, first, second, last, tryNth, tryFirst,
   trySecond, tryLast, seqEq, each, find, tryFind, contains, count, list,
   uniq, join, dict, obj, into, foldl, foldr, any, all, sum, product, map,
@@ -111,6 +111,13 @@ it('range(), range0()', () => {
 
 it('repeat()', () => {
   ckEqSeq(tryTake(repeat(2), 4), [2, 2, 2, 2]);
+
+  let x = 0;
+  const fn = () => {
+    x += 1;
+    return x;
+  };
+  ckEqSeq(tryTake(repeatFn(fn), 4), [1, 2, 3, 4]);
 });
 
 it('extend(), extend1()', () => {