Actually, the Kronecker delta function
can be defined with its domain
as any nonempty set
, so long as its codomain
is a ring
(even though its range
will be the set of 0 and 1). However, it is usually only used as described above.
For those of you whose consoles do not display backslash-escaped characters, the Kronecker delta is usually displayed as a small delta (the one that looks curvy and like a d, not the big triangle). If your browser supports HTML 4.0 in all of its glory, it should look like this: δ.