Function accumulate

Map the iterator with a function that can access the previous result. Works similar to reduce except that instead of returning a single value, we yield on every iteration and return the new iterator.

import { pipe } from "yta";
import { accumulate, of, toArray } from "yta/async";
import { asAsync, range } from "yta/sync";

await pipe(
  range(1, 6),
  asAsync()
  accumulate((sum, item) => sum + item, 0),
  toArray(),
);
// => [1, 3, 6, 10, 15]
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You can use this to create pair wise accumulation of previous and current items.

import { pipe } from "yta";
import { accumulate, drop, toArray } from "yta/async";
import { asAsync, range } from "yta/sync";

await pipe(
  range(1, 6),
  toAsync(),
  accumulate(([, last], current) => [last, current], [0, 0]),
  drop(1),
  toArray(),
);
// => [[1, 2], [2, 3], [3, 4], [4, 5]]
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See also:

• recurrent
• reduce