How to sum array of numbers in Ruby?

I have an array of integers.

For example:

array = [123,321,12389]

Is there any nice way to get the sum of them?

I know, that

sum = 0
array.each { |a| sum+=a }

would work.

For ruby >= 2.4 you can use sum:

array.sum

For ruby < 2.4 you can use inject:

array.inject(0, :+)

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

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

Try this:

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

See Ruby's Enumerable Documentation

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

array.reduce(0, :+)

While equivalent to array.inject(0, :+), the term reduce is entering a more common vernacular with the rise of MapReduce programming models.

inject, reduce, fold, accumulate, and compress are all synonymous as a class of folding functions. I find consistency across your code base most important, but since various communities tend to prefer one word over another, it’s nonetheless useful to know the alternatives.

To emphasize the map-reduce verbiage, here’s a version that is a little bit more forgiving on what ends up in that array.

array.map(&:to_i).reduce(0, :+)

Some additional relevant reading:

• http://ruby-doc.org/core-1.9.3/Enumerable.html#method-i-inject
• http://en.wikipedia.org/wiki/MapReduce
• http://en.wikipedia.org/wiki/Fold_(higher-order_function)