# collections.rb

# Arrays
# declare/initialize an Array
# nums =[]

nums = Array.new

nums[0]=52
nums[3]=39
nums[2]=nil
nums[1]="string"
puts nums
puts "======================"

thisarray = ["first", "second", "third", "second", "first"]
puts thisarray.join("**")

# non destructive uniq
puts "========== uniq ============"
puts thisarray.uniq
puts "========== original unchanged ==========="
puts thisarray

# destructive uniq
puts "============ destructive uniq =========="
thisarray.uniq!
puts thisarray

# Hashes
# declare/initialize a Hash

foodgroups = {
	'apple' => 'fruit',
	'pear' => 'fruit',
	'carrot' => 'vegetable',
	'peas' => 'vegetable',
	'pineapple' => 'fruit'
}
puts foodgroups

# add a new element or change an existing one
foodgroups['dogfood'] = '???'
foodgroups['peas'] = 'protein'

puts foodgroups

puts "======================"
foodgroups.each do |item| 
	puts item
end

puts "========== Hash Keys Only ============"
foodgroups.keys.each do |item| 
	puts item
end

puts "========== Hash Values Only ============"
foodgroups.values.each do |item|
	puts item
end

puts "========== Hash Keys and Values  ============"
foodgroups.each { |key, value|
	puts key + "=>" + value 
}

puts "========== Hash Keys Sorted ============"
# keys returns an Array
sortedbyfoodgroups = foodgroups.keys.sort_by do |item| 
	item
end

sortedbyfoodgroups.each { | food |
	puts food
}

puts "========== Hash values sorted by Key, then array in reverse order ============"
sortedbyfoodgroups = foodgroups.values.sort_by do |item| 
	item
end.reverse

sortedbyfoodgroups.each { | food |
	puts food
}