Blocks In-depth: Lambdas

invocation_arity.rb

l = lambda { |first_name, last_name| puts "Hello, #{first_name} #{last_name}!" }

l.call("Omer", "Rauchwerger") # => Hello, Omer Rauchwerger!
l.call("Omer") # => ArgumentError: wrong number of arguments (1 for 2)
l.call("Omer", "Lachish", "Rauchwerger") # => ArgumentError: wrong number of arguments (3 for 2)

invocation_return.rb

def outside
  puts "entering outside"
  l = lambda { return } # l has invocation semantics
  inside(l)
  puts "exiting outside"
end

def inside(l)
  puts "entering inside"
  l.call
  puts "exiting inside"
end
 
outside

# entering outside
# entering inside
# exiting inside
# exiting outside

stabby_operator.rb

foo = ->(name) { puts "Hello, #{name}" }
foo.call("Omer")

yield_arity.rb

p = proc { |first_name, last_name| puts "Hello, #{first_name} #{last_name}!" }

p.call("Omer", "Rauchwerger") # => Hello, Omer Rauchwerger!
p.call("Omer") # => Hello, Omer !
p.call("Omer", "Lachish", "Rauchwerger") # => Hello, Omer Lachish! 

yield_return.rb

def outside
  puts "entering outside"
  p = proc { return } # p has yield semantics
  inside(p)
  puts "exiting outside"
end

def inside(p)
  puts "entering inside"
  p.call
  puts "exiting inside"
end

outside

# entering outside
# entering inside