Ed de Almeida - 2 months ago 17

Ruby Question

Taking a look at Ruby documentation on

class I noticed something interesting and I'd like to know why it happens this way.At

`#inject`

`# Sum some numbers`

(5..10).reduce(:+) #=> 45

# Same using a block and inject

(5..10).inject { |sum, n| sum + n } #=> 45

# Multiply some numbers

(5..10).reduce(1, :*) #=> 151200

# Same using a block

(5..10).inject(1) { |product, n| product * n } #=> 151200

Notice that when

`#inject`

`p (1..5).inject(0) { |prod, n| prod * n }`

I got

`0`

But then I run

`p (1..5).inject { |sum, n| sum + n }`

p (1..5).inject { |prod, n| prod * n }

and got

`15`

120

My questions are:

a)

and

b)

`#inject`

Answer

To answer your first question:

a) **Why the documentation includes this 1 as initial value when, in fact, it is not needed?**

inject does not take 1 as initial value, from the apidock:

If you do not explicitly specify an initial value for memo, then uses the first element of collection is used as the initial value of memo.

Answer of second question lies in the answer of first itself, as it initialises the object as the first element of array on which inject is being applied.