gnus-merge
gnus-merge is an alias for `cl-merge' in `gnus-util.el
'.
(gnus-merge TYPE SEQ1 SEQ2 PREDICATE [KEYWORD VALUE]...)
Destructively merge the two sequences to produce a new sequence.
TYPE is the sequence type to return, SEQ1 and SEQ2 are the two argument
sequences, and PREDICATE is a `less-than' predicate on the elements.
Keywords supported: :key