cpp/experimental/ostream joiner/operator=

1) First, if the private "first element" flag is, insert the delimiter into the output stream  associated with this iterator as if by.

Then, unconditionally sets the "first element" flag to, and insert into the output stream as if by.

Let, , and denote the private stream pointer, delimiter, and "first element" flag members respectively, then this function is equivalent to

2-3) Implicitly declared copy/move assignment operator that copy/move assigns the private stream pointer, delimiter, and "first element" flag members.

Return value
.