Challenge 3: Proc vs Lambda Arity — Solution

add_proc = Proc.new { |a, b| a.to_i + b.to_i }
add_lambda = lambda { |a, b| a + b }

puts add_proc.call(5)     # Proc: missing arg silently becomes nil

begin
  add_lambda.call(5)      # Lambda: raises ArgumentError instead
rescue ArgumentError => e
  puts "Lambda raised: #{e.message}"
end

=begin
Output:
5
Lambda raised: wrong number of arguments (given 1, expected 2)

Notes:
- add_proc.call(5) does NOT raise an error. The Proc is lenient about
  argument count: b simply becomes nil since no second argument was given.
  .to_i is used here so nil.to_i (which is 0) doesn't crash the addition —
  without it, a + b would raise a NoMethodError trying to add nil.
- add_lambda.call(5) DOES raise an ArgumentError immediately, the same way
  calling an ordinary method with the wrong number of arguments would.
  Lambdas enforce strict arity; Procs do not.
- This is exactly the "strict vs lenient" distinction from the chapter,
  and it's a real reason to prefer lambdas when a caller passing the wrong
  number of arguments should fail loudly instead of silently producing a
  wrong result.
=end