function cellToChildPos(h3Index, parentRes) {
    const [lower, upper] = h3IndexToSplitLong(h3Index);
    const childPos = C._malloc(SZ_INT64);
    try {
        throwIfError(H3.cellToChildPos(lower, upper, parentRes, childPos));
        return readInt64AsDoubleFromPointer(childPos);
    } finally {
        C._free(childPos);
    }
}
Get the position of the cell within an ordered list of all children of the
cell's parent at the specified resolution.
@static
@param  {H3IndexInput} h3Index  H3 index to get child pos for
@param  {number} parentRes      Resolution of reference parent
@return {number}                Position of child within parent at parentRes
@throws {H3Error}               If cell or parentRes are invalid