timothydowd/enumerables

enumerables

Project 2: Enumerable Methods

You learned about the Enumerable module that gets mixed into the Array and Hash classes (among others) and provides you with lots of handy iterator methods. To prove that there’s no magic to it, you’re going to rebuild those methods. Assignment

Create a script file to house your methods and run it in IRB to test them later.
Add your new methods onto the existing Enumerable module. Ruby makes this easy for you because any class or module can be added to without trouble … just do something like:

module Enumerable def my_each # your code here end end

Create #my_each, a method that is identical to #each but (obviously) does not use #each. You’ll need to remember the yield statement. Make sure it returns the same thing as #each as well.
Create #my_each_with_index in the same way.
Create #my_select in the same way, though you may use #my_each in your definition (but not #each).
Create #my_all? (continue as above)
Create #my_any?
Create #my_none?
Create #my_count
Create #my_map
Create #my_inject
Test your #my_inject by creating a method called #multiply_els which multiplies all the elements of the array together by using #my_inject, e.g. multiply_els([2,4,5]) #=> 40
Modify your #my_map method to take a proc instead.
Modify your #my_map method to take either a proc or a block. It won’t be necessary to apply both a proc and a block in the same #my_map call since you could get the same effect by chaining together one #my_map call with the block and one with the proc. This approach is also clearer, since the user doesn’t have to remember whether the proc or block will be run first. So if both a proc and a block are given, only execute the proc.

Quick Tips:

Remember yield and the #call method.

enumerables's Issues

my_inject method does not work as expected

enumerables/enumerable.rb

Line 158 in 97cf2b6

def my_inject(*args)

To satisfy that your my_inject enumerable method works as expected, it must pass the following tests;

puts %w[long short thick thin].my_inject('a', 'b')

puts (5..10).my_inject(:+)                             #=> 45
# Same using a block and inject
puts (5..10).my_inject { |sum, n| sum + n }            #=> 45
# Multiply some numbers
puts (5..10).my_inject(1, :*)                          #=> 151200
# Same using a block
puts (5..10).my_inject(1) { |product, n| product * n } #=> 151200
# find the longest word
longest = %w{ cat sheep bear commando }.my_inject do |memo, word|
   memo.length > word.length ? memo : word
end
puts longest

Refer to the official inject documentation for more details