Iterators

Iterators in Ruby

Ruby's arrays come with powerful iterator methods that take a block — code between { } or do...end:

each

Runs a block for every element:

[1, 2, 3].each { |n| puts n * 2 }
# 2
# 4
# 6

map

Transforms each element, returns a new array:

squares = [1, 2, 3, 4].map { |n| n ** 2 }
puts squares.inspect  # [1, 4, 9, 16]

select / reject

Filter elements based on a condition:

evens = (1..10).select { |n| n.even? }
odds = (1..10).reject { |n| n.even? }
puts evens.inspect  # [2, 4, 6, 8, 10]

reduce

Accumulate a value across all elements:

total = [1, 2, 3, 4, 5].reduce(0) { |sum, n| sum + n }
puts total  # 15

Your Task

Given numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]:

1. Use map to double each number; print joined with ", "
2. Use select to get even numbers; print joined with ", "
3. Use reduce to sum all numbers; print the total