Exploring tally, group_by, and transform_values methods in Ruby.

tally Method:

The tally method is available in Ruby 2.7 or later versions.

It is used to count the occurrences of elements in an enumerable object and returns a hash with the elements as keys and their respective counts as values.

 arr = [1, 2, 3, 2, 1, 1, 3, 4, 5, 4, 3]
 => [1, 2, 3, 2, 1, 1, 3, 4, 5, 4, 3]

 arr.tally # here we get the value as a count of the value
 => {1=>3, 2=>2, 3=>3, 4=>2, 5=>1}

group_by Method:

The group_by method is a built-in Ruby method available on enumerable objects.

It groups the elements based on a given block and returns a hash where the keys are the grouping criteria and the values are arrays containing the elements that match each criterion.

arr = [1, 2, 3, 4, 5]
 => [1, 2, 3, 4, 5]

arr.group_by {|num| num%2}
 => {1=>[1, 3, 5], 0=>[2, 4]}

transform_values Method:

The transform_values method is available in Ruby 2.4 or later versions.

It is used to transform the values of a hash based on a given block and returns a new hash with the transformed values.

hash = { a: 1, b: 2, c: 3 }
 => {:a=>1, :b=>2, :c=>3}

 result = hash.transform_values { |value| value * 2 }
 => {:a=>2, :b=>4, :c=>6}