arrays

# Arrays: ordered, growable, one element type.

numbers = [3, 1, 4, 1, 5]
puts numbers.size
puts numbers[0]
puts numbers.first
puts numbers.last

numbers << 9          # append
puts numbers

# The common questions.
puts numbers.includes?(4)
puts numbers.sum
puts numbers.sorted
puts numbers.select { |n| n > 2 }
puts numbers.map { |n| n * 10 }
puts numbers.reduce(0) { |acc, n| acc + n }

# An empty array needs its element type written down.
names = [] of String
names << "Ayşe"
names << "Mehmet"
puts names.join(", ")

# Walk with an index.
names.each_with_index { |name, i| puts "#{i + 1}. #{name}" }