Where and when to use Lambda?

Question

I am trying to understand why do we really need lambda or proc in ruby (or any other language for that matter)?

#method
def add a,b
  c = a+b
end

#using proc
de         


        

Answer 1

1) It is just a convenience. You don't need to name certain blocks

special_sort(array, :compare_proc => lambda { |left, right| left.special_param <=> right.special_param }

(imagine if you had to name all these blocks)

2) #lambda is usually used to create clojures:

def generate_multiple_proc(cofactor)
  lambda { |element| element * cofactor }
end

[1, 2, 3, 4].map(&generate_multiple_proc(2)) # => [2, 3, 5, 8]

[1, 2, 3, 4].map(&generate_multiple_proc(3)) # => [3, 6, 9, 12]