How to sum array of numbers in Ruby?

Ruby 2.4+ / Rails - `array.sum` i.e. `[1, 2, 3].sum # => 6`

Ruby pre 2.4 - `array.inject(:+)` or `array.reduce(:+)`

*Note: The `#sum` method is a new addition to 2.4 for `enumerable` so you will now be able to use `array.sum` in pure ruby, not just Rails.

**Method 1:**

[1] pry(main)> [1,2,3,4].sum
=> 10
[2] pry(main)> [].sum
=> 0
[3] pry(main)> [1,2,3,5,nil].sum
TypeError: nil can't be coerced into Integer

**Method 2:**


[24] pry(main)> [].inject(:+)
=> nil
[25] pry(main)> [].inject(0, :+)
=> 0
[4] pry(main)> [1,2,3,4,5].inject(0, :+)
=> 15
[5] pry(main)> [1,2,3,4,nil].inject(0, :+)
TypeError: nil can't be coerced into Integer
from (pry):5:in `+'

**Method 3:**

[6] pry(main)> [1,2,3].reduce(:+)
=> 6
[9] pry(main)> [].reduce(:+)
=> nil
[7] pry(main)> [1,2,nil].reduce(:+)
TypeError: nil can't be coerced into Integer
from (pry):7:in `+'
**Method 4:**
When Array contains an nil and empty values, by default if you use any above functions reduce, sum, inject everything will through the

> TypeError: nil can't be coerced into Integer

You can overcome this by,

[16] pry(main)> sum = 0
=> 0
[17] pry(main)> [1,2,3,4,nil, ''].each{|a| sum+= a.to_i }
=> [1, 2, 3, 4, nil, ""]
[18] pry(main)> sum
=> 10

**Method 6:**
**eval**



Evaluates the Ruby expression(s) in string.


[26] pry(main)> a = [1,3,4,5]
=> [1, 3, 4, 5]
[27] pry(main)> eval a.join '+'
=> 13
[30] pry(main)> a = [1,3,4,5, nil]
=> [1, 3, 4, 5, nil]
[31] pry(main)> eval a.join '+'
SyntaxError: (eval):1: syntax error, unexpected end-of-input
1+3+4+5+

for array with nil values we can do compact and then inject the sum
ex-

a = [1,2,3,4,5,12,23.45,nil,23,nil]
puts a.compact.inject(:+)

For Ruby >=2.4.0 you can use `sum` from Enumerables.

[1, 2, 3, 4].sum

It is dangerous to mokeypatch base classes. If you like danger and using an older version of Ruby, you could add `#sum` to the `Array` class:

class Array
def sum
inject(0) { |sum, x| sum + x }
end
end

If you feel golfy, you can do

eval [123,321,12389]*?+

This will create a string "123+321+12389" and then use function eval to do the sum. This is **only for golfing purpose**, you should not use it in proper code.

**For ruby >= 2.4** you can use [sum][1]:

`array.sum`

**For ruby < 2.4** you can use [inject][2]:

array.inject(0, :+)

Note: the `0` base case is needed otherwise `nil` will be returned on empty arrays:

> [].inject(:+)
nil
> [].inject(0, :+)
0


[1]:

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[2]:

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Try this:

array.inject(0){ |sum, x| sum + x }

[See Ruby's Enumerable Documentation][1]


[1]:

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(note: the `0` base case is needed so that `0` will be returned on an empty array instead of `nil`)