(quote +,Tally,Tally)

x + y -- produces the union of two tallies.

One of the arguments may be a Set.

i1 : x = tally {a,a,a,b,b,c}



o1 = Tally{a => 3}

           b => 2

           c => 1



o1 : Tally

i2 : y = tally {b,c,c,d,d,d}



o2 = Tally{b => 1}

           c => 2

           d => 3



o2 : Tally

i3 : x + y



o3 = Tally{a => 3}

           b => 3

           c => 3

           d => 3



o3 : Tally