Learning Outcome

What learning outcomes did you focus on today? What did you learn?

Over the weekend, I spent most of my time Practising more medium level Ruby Algorithm/Katas on Exercism.io. These exercises have enabled me to get more grasp of how Ruby operates behind the scene, understand some Ruby syntax, its application, and TDD. While pairing with my mentor earlier today, he looked at some of my Algorithm solutions and took me through better ways to arrive at a more streamlined solution, this led to a couple of refactoring, writing a lesser line of code to arrive at the same solution. Below are some cool Ruby Syntax/methods and its application.

- Inject.

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator. If you specify a block, then for each element in enum the block is passed an accumulator value (sum) and the element.

- any?.

Passes each element of the collection to the given block. The method returns true if the block ever returns a value other than false or nil. If the block is not given, Ruby adds an implicit block of { |obj| obj } that will cause any? to return true if at least one of the collection members is not false or nil.

Example.

Given a number, find the sum of all the unique multiples of particular numbers up to

but not including that number. My initial solution was;

    class SumOfMultiples

          def initialize(*multiples)

                 @multiples = multiples.   

         end

         def to(limit)

                 result = [ ]

                @multiples.each do |multiple|

                     (1..(limit - 1).each do |range|

                         if (range % multiple == 0)

                             result.push(range)

                        end

                      end

               end

               result.uniq.sum

           end

    end

A better way to streamline the previous solution would be;

    class SumOfMultiples

            def initialize(*multiples)

                    @multiples = multiples

            end

            def to(limit)

               (1...limit).inject(0) do |sum, range|

                    if(@multiples.any?{|multiple| range % multiple == 0})

                        sum + range

                      else.

                         sum

                      end

                 end

            end
       end

The second solution avoids the use of multiple loops and continuous appending of the correct range to the result array before calculating the sum total. Rathers through a binary operation parses an accumulator value (sum) and the element. The enum any? on the other hand, check if certain elements in that array match the criteria in the block.

- “&” Ampersand parameter.

Here’s what the &object does,

• If the object is a block, it converts it to a Proc
• If the object is a Proc, it converts it to a block
• If the object is something else, it calls to Proc on it and then converts it to a block

What’s something that surprised you today?

Anytime you want to do a loop in Ruby, there’s is always a better way to go about it - Doug Bradbury

What’s something that frustrated you today?

The medium level Algorithm/Katas involves a lot of head cracking 😀

Reference

Ruby-docs Exercism.io splat-operator-in-Ruby