Challenge 1: Refactor to Idiomatic Ruby — Solution

# Before:
# evens = []
# [1,2,3,4,5,6].each { |n| if n.even? then evens.push(n) end }

# After:
evens = [1, 2, 3, 4, 5, 6].select(&:even?)
puts evens.inspect

# Before:
# status = nil
# if age < 18 then status = "minor" else status = "adult" end

# After:
age = 25
status = age < 18 ? "minor" : "adult"
puts status

=begin
Output:
[2, 4, 6]
adult

Notes:
- select(&:even?) replaces the manual accumulator entirely: no evens = []
  declared beforehand, no .push inside a block — .select already returns
  a new array containing just the elements where the block is truthy.
- The ternary (age < 18 ? "minor" : "adult") replaces both the temp
  variable (status = nil) and the if/else reassigning it in two branches,
  collapsing to one direct assignment. A full if/elsif/else-as-expression
  would work identically here too; the ternary is simply the more compact
  choice for a two-branch, single-expression case like this one.
- Both rewrites follow the chapter's checklist items: prefer Enumerable
  over manual loops, and use if/case (or the ternary) as an expression
  instead of a temp variable mutated across branches.
=end