Difference between Proc and Lambda

proc_and_lambda.rb

# Procs and Lambdas. They are both a Proc object.
#
# The main differences:
#
# 1- Lamdbas are strict about argument number instead of Procs.
# 2- Lambda :return returns out the scope. Proc :return returns out of the calling scope.

# Lamdbas are strict about argument number instead of Procs.
l = lambda { |word| puts word }

l.call('Mehdi')            # output: Mehdi
l.call('Mehdi', 'Farsi')   # ArgumentError: wrong number of arguments (2 for 1)

p = Proc.new { |word| puts word }

p.call('Mehdi', 'Farsi')   # output: Mehdi

# Lambda :return exits out the scope.
# Proc :return exits out of the calling scope.

def lambda_return_test
  puts "Before lambda call."
  lambda {return}.call
  puts "After lambda call."
end

def proc_return_test
  puts "Before proc call."
  Proc.new {return}.call
  puts "After proc call."
end

lambda_return_test        # output: Before lambda call. After lambda call.
proc_return_test          # output: Before proc call.