Challenge 2: reduce for a Shopping Total — Solution

cart = [
  { item: "Book", price: 12.99 },
  { item: "Pen", price: 1.50 },
  { item: "Notebook", price: 4.25 }
]

# Explicit block
total = cart.reduce(0) { |sum, entry| sum + entry[:price] }
puts total

# Shorthand: map out the prices first, then reduce(:+)
total_shorthand = cart.map { |entry| entry[:price] }.reduce(:+)
puts total_shorthand

=begin
Output:
18.74
18.74

Notes:
- The explicit-block version starts the accumulator (sum) at 0 and adds
  each entry's :price on every step of the reduce.
- The shorthand version first uses .map to pull out just the price from
  each hash into a plain array ([12.99, 1.50, 4.25]), then calls
  reduce(:+) with no block at all — the symbol :+ tells reduce which
  operator to fold the array with.
- reduce(:+) only works cleanly here because .map already reduced the data
  down to a flat array of numbers; reduce(:+) can't reach inside a hash on
  its own the way the explicit block version can.
=end