CODEWITHSUNDEEP
ruby
MrPizzaFace
MrPizzaFace

Reputation: 8086

Error accessing an array's value by it's index?

Trying to sum up all the numbers in an array. Example 10 + 20 + 30 should be 60. 

def sum *arr
  i=0
  total=0
  while i <= arr.count
    total += arr[i]
    i+=1
  end
  total
end

puts sum(10,20,30)

Why am I getting this error. This code looks like it should work to me. What am I doing wrong? Why wont it let me access the array value by it's index? 

p8.rb:23:in `+': nil can't be coerced into Fixnum (TypeError)
        from p8.rb:23:in `sum'
        from p8.rb:29:in `<main>'

Upvotes: 1

Views: 69

Answers (3)

user3191440
user3191440

Reputation: 1

Matt's answer is both slick and correct, but you hit the error because ruby zero indexes arrays. So if you changed the count condition while i <= arr.count - 1

your error would go away

Upvotes: 0

Kal
Kal

Reputation: 2664

Matt's answer gives you the canonical Ruby way to sum, using inject. But if you're not ready to learn inject, at least save yourself the trouble of manually keeping track of array indexes (where your actual problem lies!) by using #each to iterate through the array like so:

def sum *arr
  total = 0
  arr.each do |x|
    total += x
  end
  total
end

puts sum(10,20,30) # => 60

Upvotes: 1

Matt
Matt

Reputation: 20776

Change

while i <= arr.count

to

while i < arr.count

arr[arr.count] is always out of bounds.

Fyi a shorter way to write sum is:

def sum *arr
  arr.inject(:+)
end

Upvotes: 7

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