Question

So I really like this syntax in Lisp:

 (+ 1 1 2 3 5 8 13)
 => 33

I want to add a list of items in Ruby and would like to approximate this as best as possible.
Right now, my best solution involves an array and the collect/map method.

So:

sum = 0; [1,1,2,3,5,8,13].collect { |n| sum += n }

BUT…

I would like to add methods to this which could return nil.

sum = 0; [1, booking_fee, 8,13].collect { |n| n = 0 if n.nil?; sum += n }

And it would be really nice to do this, where all of the lines in the middle refer to methods that may return nil, but I can’t exactly build an array in this manner. This is just an idea of what I want my syntax to look like.

def total
  Array.new do
    booking_fee
    rental_charges
    internationalization_charges
    discounts
    wild_nights
  end.collect { |n| n = 0 if n.nil?; sum += n }
end

Any suggestions before I try to hack away and effectuate Greenspun’s Rule? (Programming is indeed a compulsion.

Answer 1

• There is already a method inject for doing what you want.
• Changing nil to a number without affecting a number is easy: use to_i (or to_f if you are dealing with float).

.

[
  booking_fee,
  rental_charges,
  internationalization_charges,
  discounts,
  wild_nights,
].inject(0){|sum, item| sum + item.to_i}