const xor = (a, b) => Boolean(a) !== Boolean(b);
const and = (a, b) => Boolean(a) && Boolean(b);

const toBit = predicate => (a, b) => (predicate(a, b) ? 1 : 0);
const xorBit = toBit(xor);
const andBit = toBit(and);

const halfAdder = (a, b) => ({ c: andBit(a, b), s: xorBit(a, b) });