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export function* map(xs, fn) {
for (const x of xs) {
yield fn(x);
}
}
export function reduce(xs, fn, initial) {
let value = initial;
for (const x of xs) {
value = fn(value, x);
}
return value;
}
export function* chunkBy(xs, keyFn, coalesceFn) {
let chunk;
let key;
for (const x of xs) {
const newKey = keyFn(x);
if (key === undefined) {
chunk = [x];
} else if (coalesceFn(key, newKey)) {
chunk.push(x);
} else {
yield { key, chunk };
chunk = [x];
}
key = newKey;
}
if (chunk !== undefined) {
yield { key, chunk };
}
}
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