BigBinary Blog

Ruby 2.7 adds Enumerable#tally

Let's say that we have to find the frequency of each element of an array.

Before Ruby 2.7, we could have achieved it using group_by or inject.

1irb> scores = [100, 35, 70, 100, 70, 30, 35, 100, 45, 30]
2
3# we can use group_by to group the scores
4
5irb> scores.group_by { |v| v }.map { |k, v| [k, v.size] }.to_h
6=> {100=>3, 35=>2, 70=>2, 30=>2, 45=>1}
7
8# or we can use inject to group the scores
9
10irb> scores.inject(Hash.new(0)) {|hash, score| hash[score] += 1; hash }
11=> {100=>3, 35=>2, 70=>2, 30=>2, 45=>1}
12

Ruby 2.7

Ruby 2.7 adds Enumerable#tally which can be used to find the frequency. Tally makes the code more readable and intuitive. It returns a hash where keys are the unique elements and values are its corresponding frequency.

1
2irb> scores = [100, 35, 70, 100, 70, 30, 35, 100, 45, 30]
3irb> scores.tally
4=> {100=>3, 35=>2, 70=>2, 30=>2, 45=>1}
5

Check out the github commit for more details on this.