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using_ranges_as_hash_keys

🗝️ Use Ranges as Hash Keys (and Avoid Pitfalls)​

Ruby allows Range objects as hash keys, but beware: hash and eql? depend on both endpoints and exclusivity. Two ranges with identical boundaries but different exclusivity are distinct; use cover? in your lookup logic to abstract those nuances.

pricing = {
  (0..10)   => "$",
  (11..20)  => "$$",
  (21...30) => "$$$"
}

def price_for(qty, table)
  # direct lookup fails for exclusivity mismatches
  entry = table.find { |range, _| range.cover?(qty) }
  entry&.last
end

puts price_for(20, pricing)  # => "$$"