  Multisets are an intuitive extension of the traditional concept of sets that
allow repetition of elements, with the number of times each element appears
being understood as the respective multiplicity. Recent generalizations of
multisets to real-valued functions, accounting for possibly negative values,
have paved the way to a number of interesting implications and applications,
including respective implementations as electronic systems. The basic multiset
operations include the set complementation (sign change), intersection (minimum
between two values), union (maximum between two values), difference and sum
(identical to the algebraic counterparts). When applied to functions or
signals, the sign and conjoint sign functions are also required. Given that
signals are functions, it becomes possible to effectively translate the
multiset and multifunction operations to analog electronics, which is the
objective of the present work. It is proposed that effective multiset
operations capable of high performance self and cross-correlation can be
obtained with relative simplicity in either discrete or integrated circuits.
The problem of switching noise is also briefly discussed. The present results
have great potential for applications and related developments in analog and
digital electronics, as well as for pattern recognition, signal processing, and
deep learning.
