VirtualTally + VirtualTally -- union of tallies

• Operator: +

Description

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

One of the arguments may be a Set.

 i1 : x = tally {a,b,b,c,c,c,d,d,d} o1 = Tally{a => 1} b => 2 c => 3 d => 3 o1 : Tally i2 : y = tally {a,a,a,b,b,c,d} o2 = Tally{a => 3} b => 2 c => 1 d => 1 o2 : Tally i3 : x' = new VirtualTally from x o3 = VirtualTally{a => 1} b => 2 c => 3 d => 3 o3 : VirtualTally i4 : y' = new VirtualTally from y o4 = VirtualTally{a => 3} b => 2 c => 1 d => 1 o4 : VirtualTally i5 : z' = y' - x' o5 = VirtualTally{a => 2 } c => -2 d => -2 o5 : VirtualTally i6 : z' + x' o6 = VirtualTally{a => 3} b => 2 c => 1 d => 1 o6 : VirtualTally i7 : z' + y' o7 = VirtualTally{a => 5 } b => 2 c => -1 d => -1 o7 : VirtualTally