Package detail

/**

• callbag-scan

• ---

  *
• Callbag operator that combines consecutive values from the same source.
• It's essentially like array .reduce, but delivers a new accumulated value
• for each value from the callbag source. Works on either pullable or
• listenable sources. *
• npm install callbag-scan *
• Example: *
• const fromIter = require('callbag-from-iter');
• const iterate = require('callbag-iterate');
• const scan = require('callbag-scan'); *
• const iterSource = fromIter([1,2,3,4,5]);
• const scanned = scan((prev, x) => prev + x, 0)(iterSource); *
• scanned(0, iterate(x => console.log(x))); // 1
• // 3
• // 6
• // 10
• // 15 */

function scan(reducer, seed) { let hasAcc = arguments.length === 2; return source => (start, sink) => { if (start !== 0) return; let acc = seed; source(0, (t, d) => { if (t === 1) { acc = hasAcc ? reducer(acc, d) : ((hasAcc = true), d); sink(1, acc); } else sink(t, d); }); }; }

module.exports = scan;