CODEWITHSUNDEEP
ruby
leemour
leemour

Reputation: 12073

Each with index with object in Ruby

I am trying to iterate over an array and conditionally increment a counter. I am using index to compare to other array's elements:

elements.each_with_index.with_object(0) do |(element, index), diff|
  diff += 1 unless other[index] == element
end

I can't get diff to change value even when changing it unconditionally. This can be solved with inject: 

elements.each_with_index.inject(0) do |diff, (element, index)|
  diff += 1 unless other[index] == element
  diff
end

But I am wondering if .each_with_index.with_object(0) is a valid construction and how to use it?

Upvotes: 0

Views: 2548

Answers (2)

Stefan
Stefan

Reputation: 114248

You want to count the number of element wise differences, right?

elements = [1, 2, 3, 4, 5]
other    = [1, 2, 0, 4, 5]
#                 ^

I'd use Array#zip to combine both arrays element wise and Array#count to count the unequal pairs:

elements.zip(other).count { |a, b| a != b }  #=> 1

Upvotes: 2

tihom
tihom

Reputation: 8003

From ruby docs for each_with_object

Note that you can’t use immutable objects like numbers, true or false as the memo. You would think the following returns 120, but since the memo is never changed, it does not.

(1..5).each_with_object(1) { |value, memo| memo *= value } # => 1

So each_with_object does not work on immutable objects like integer.

Upvotes: 6

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