@Section
   @Title { "@Null" }
   @Tag { null }
@Begin
@PP
This symbol
null.sym @Index { @@Null symbol }
provides a convenient way to remove unwanted
concatenation symbols.  If there is a concatenation symbol
preceding @@Null, the @@Null and the
concatenation symbol are both deleted.  Otherwise, if there is a
following concatenation symbol, it and the @@Null are both deleted.
Otherwise, @@Null becomes an empty object.
@PP
These rules apply to a fully parenthesized version of the expression.  For
example, in
@ID @Code {
"...  //1vx @Null |0.5i ..."
}
it is the horizontal concatenation symbol following @@Null that
disappears, because in the fully parenthesized version
@ID @Code {
"...  //1vx { @Null |0.5i ... }"
}
there is no concatenation symbol preceding the @@Null.
@End @Section
