lilit
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JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
function iterator(xs) {
const it = xs[Symbol.iterator]();
if (!it[Symbol.iterator])
it[Symbol.iterator] = () => it;
return it;
}
exports.iterator = iterator;
function asyncIterator(xs) {
const it = xs[Symbol.asyncIterator]();
if (!it[Symbol.asyncIterator])
it[Symbol.asyncIterator] = () => it;
return it;
}
exports.asyncIterator = asyncIterator;
function forAwaitableIterator(xs) {
return xs[Symbol.asyncIterator] ? asyncIterator(xs) : iterator(xs);
}
exports.forAwaitableIterator = forAwaitableIterator;
function isIterator(xs) {
return xs && xs[Symbol.iterator] && xs[Symbol.iterator]() === xs;
}
exports.isIterator = isIterator;
function isAsyncIterator(xs) {
return xs && xs[Symbol.asyncIterator] && xs[Symbol.asyncIterator]() === xs;
}
exports.isAsyncIterator = isAsyncIterator;
function isForOfAwaitableIterator(xs) {
return isAsyncIterator(xs) || isIterator(xs);
}
exports.isForOfAwaitableIterator = isForOfAwaitableIterator;
// https://stackoverflow.com/a/46416353/870615
function tee(it) {
// If `it` is not an iterator, i.e. can be traversed more than once,
// we just return it unmodified.
if (!isIterator(it))
return [it, it];
const source = it;
const buffers = [[], []];
const DONE = Symbol('done');
const next = (i) => {
if (buffers[i].length)
return buffers[i].shift();
const x = source.next();
if (x.done)
return DONE;
buffers[1 - i].push(x.value);
return x.value;
};
function* buffer2Iterable(i) {
while (true) {
const x = next(i);
if (x === DONE)
break;
yield x;
}
}
return [buffer2Iterable(0), buffer2Iterable(1)];
}
exports.tee = tee;
function asyncTee(it) {
if (!isForOfAwaitableIterator(it))
return [it, it];
const source = it;
const buffers = [[], []];
const DONE = Symbol('done');
const next = async (i) => {
if (buffers[i].length)
return buffers[i].shift();
const x = await source.next();
if (x.done)
return DONE;
buffers[1 - i].push(x.value);
return x.value;
};
async function* buffer2AsyncIterable(i) {
while (true) {
const x = await next(i);
if (x === DONE)
break;
yield x;
}
}
return [buffer2AsyncIterable(0), buffer2AsyncIterable(1)];
}
exports.asyncTee = asyncTee;
// TODO: more performant impl?
function teeN(it, n = 2) {
const res = [];
let orig = it;
let copy;
for (let i = 0; i < n - 1; i++) {
[orig, copy] = tee(orig);
res.push(copy);
}
res.push(orig);
return res;
}
exports.teeN = teeN;
function asyncTeeN(it, n = 2) {
const res = [];
let orig = it;
let copy;
for (let i = 0; i < n - 1; i++) {
[orig, copy] = asyncTee(orig);
res.push(copy);
}
res.push(orig);
return res;
}
exports.asyncTeeN = asyncTeeN;
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