Write to this stream the one‐byte type indicator for an eight‐byte double‐precision floating‐point number and the eight‐byte IEEE double‐precision floating‐point number (in network byte order) comprised of the most‐significant eight bytes of the specified value (in host byte order), and return a reference to this stream. If this stream is initially invalid, this operation has no effect. If the next output operation has been set to be marked invalid (see makeNextInvalid), reset this marking and emit the invalid indicator instead of the type indicator. Note that for non‐conforming platforms, this operation may be lossy.