tally

tally x -- tallies the frequencies of items in a list x.

It produces an hash table (multiset) y which tallies the frequencies of occurrences of items in the list x, i.e., y_i is the number of times i appears in x, or is 0 if i doesn't appear in the list.

i1 : y = tally {1,2,3,a,b,1,2,a,1,2,{a,b},{a,b},a}



o1 = Tally{1 => 3     }

           2 => 3

           3 => 1

           a => 3

           b => 1

           {a, b} => 2



o1 : Tally

i2 : y_{a,b}



o2 = 2