power_of_enumerables.rb

# TODO: Print the elements at indices 1, 3, 5, 7, etc. on separate lines.
#       You should make use of Enumerable#each_with_index
def print_odd_indexed_integers(array)
  array.each_with_index { |x, i| puts x if i.odd? }
end

# TODO: Return the odd numbers from a list of integers.
#       You should make use of Enumerable#select
def odd_integers(array)
  # array.select(&:odd?)
  array.select { |x| x.odd? }
end

# TODO: Return the first number from an Array that is less than a particular number - 'limit.'
#       You should make use of Enumerable#find
def first_under(array, limit)
  array.find { |x| x < limit }
end

# TODO: Take an Array of Strings and return a new Array with an exclamation point appended to each String.
#       You should make use of Enumerable#map
def add_bang(array)
  array.map { |x| x + '!' }
end

# TODO: Calculate the sum of an Array of numbers.
#       You should make use of Enumerable#reduce
def sum(array)
  # array.reduce(:+)
  array.reduce { |sum, x| sum += x }
end

# TODO: Reorganize an Array of the elements into groups of 3, and then sort each group alphabetically.
#       You should make use of Enumerable#each_slice
def sorted_triples(array)
  # array.each_slice(3).map(&:sort)
  array.each_slice(3).map {|x| x.sort}
end

# Driver code... don't change this.
print_odd_indexed_integers([2, 4, 6, 8, 10, 12]) # this should print "4\n8\n12"

puts odd_integers([3, 4, 7, 9, 10, 16]) == [3, 7, 9]

puts first_under([13, 21, 7, 0, 11, 106], 10) == 7

puts add_bang(["hi", "mom"]) == ["hi!", "mom!"]

puts sum([1, 1, 2, 3, 5]) == 12

words = %w(the salted pork is particularly good)
puts sorted_triples(words) == [["pork", "salted", "the"],
                               ["good", "is", "particularly"]]