@Section
   @Title { "@Common" and "@Rump" }
   @Tag { rump }
@Begin
@PP
common.sym @Index { @@Common symbol }
rump.sym @Index { @@Rump symbol }
The @@Common and @@Rump symbols compare two paragraph objects:
@ID @Code "{ Aardvark, 29 } @Common { Aardvark, 359 }"
If either parameter is not a paragraph object, it is converted into
a single-object paragraph first.  The result of @@Common is the
common prefix of the two paragraphs; that is, those initial objects
which are equal in the two paragraphs.  In the example above, the
result is {@Code "Aardvark,"}.  The result of @@Rump is that part of
the second object which is not included in @@Common; the result of
@ID @Code "{ Aardvark, 29 } @Rump { Aardvark, 359 }"
is {@Code "359"}.
@PP
If the two objects have nothing in common, the result of @@Common will
be an empty object and the result of @@Rump will be the second
object.  If the two objects are identical, the result of @@Common will
be the first object, and the result of @@Rump will be an empty object.
@PP
The only known use for @@Rump is to implement merged index entries
(Section {@NumberOf sorted}), and @@Common, although included for
completeness, has no known use at all.
@End @Section
