In the README (Question 5), it says: "Build a method reverse_array that takes in an array of integers...", but the test in the spec is as follows:

  describe '#reverse_array' do
    it 'reverse the order of an array' do
      expect(reverse_array(["blake", "ashley", "scott"])).to eq(["scott", "ashley", "blake"])
    end
  end

...which tests it against an array of strings, not integers. Shouldn't really affect anything, but the semantics are clearly off.

@SophieDeBenedetto @deniznida

The method #sort_array_char_count is intended to teach students that they can modify default sorting behavior by passing a block to #sort or using #sort_by. The spec tests this functionality with the array ["dogs", "cat", "horses"]. Calling ruby's #sort with the default lexicographic ordering for Strings results in the same output as if the student sorted the array by length of string as intended. Both sortings output ["cat", "dogs", "horses"].

This can lead to confusion. Working with a student now whose code looks like this:

def sort_array_char_count(array)
  sorted_array = []
  array.each do |word|
    sorted_array.push(word.length)
  end.sort
end

This passes the spec even though it returns a lexicographic sort. I will have to explain to them that their sorted_array is never actually being returned (not to mention it is an array of integers). While this is a "teachable moment", the spec leads to a false positive and the student has not grasped the lesson.

Proposed fix: change array to ["dogs", "cat", "horses", "armadillo"]

the directions for bonus collections practice do not match the spec (ex: on learn, question # 3 is sort_array_char_count but the spec is looking for swap_elements) change in the curriculum?

The lab should only download with the spaces for the code to be entered.

there are eight rspecs for this module but the lesson calls for nine methods to be built. The method that is missing an rspec is sort_array_char_count

User: Artem Eremin

Batch: 000

Bug Description: Page: https://learn.co/tracks/web-development-with-ruby-on-rails/ruby/a-deeper-dive-into-enumerables/bonus-collections-practice-1

Section: QUESTION 3: #SWAP_ELEMENTS Code: swap_elements_from_to(["a", "b", "c"],0,3) #=> ["c", "b", "a"]

Bug: actually, such call doesn't make sence, because if destination_index equals 3 then it's beyond the array, so this call should return nil or even raise an Error. Anyway, even if we call swap_elements_from_to(["a", "b", "c"],0,2) to be correct with indexes, it should return ["b", "c", "a"] instead of ["c", "b", "a"] provided in the comment

we never discussed sorting so maybe a brief intro and then some resources before they start this lab.

we haven't covered hashes yet.

The lab shows question 4 being the swap method and question 5 being the reverse method but the rspec tests are reversed (4 is reverse and 5 is swap) so there will be confusion even though in the end all tests have to be run anyway.

From the README:

QUESTION 8: #SUM_ARRAY
Build a method sum_array that adds together all of the integers in the array and returns their sum.
Advanced: Try using either the .inject method or the .each_with_object method here.

if you try to use #each_with_object to sum an array the return value will be 0 (or whatever the starting sum is) due to the way instances of the Fixnum class don't change. Each integer value is a different Fixnum object. #each_with_object` returns the original object passed in which will always be 0

(1..10).to_a.each_with_object(0) do |num, sum|
  sum += num
end
#= > 0

You could do something like

(1..10).to_a.each_with_object({sum: 0}) do |num, hash|
  hash[:sum] += num
end[:sum]
#= > 55

but that's sort of roundabout and confusing to students at this point in the curriculum

Maybe sort a list of strings by the number of characters?

That way it actually requires them to really understand and use the sort method.