RoR / Ruby delete nil elements from nested array

Question

To split an array into two equal pieces I would do this,

>> a = [1,2,3,4,5]
=> [1, 2, 3, 4, 5]
>> a.in_groups_of( (a.size/2.0).ceil ) if a.size > 0
=> [[1, 2, 3], [4, 5, nil]]

Now I've got a nested array that contains nil elements if the size of the array is odd. How can I remove the nil elements from the nested arrays? I want to do something like,

a.compact

But unfortunately that doesn't work, ruby only removes nil elements on the first level and not recursively. Does ruby provide any nice solutions for this problem?

Answer 1

With Ruby 1.8.7 and later you can do the following:

a.each &:compact!
=> [[1, 2, 3], [4, 5]]

With Ruby 1.8.6, you have do do this the long way:

a.each {|s| s.compact!}

Both of these will modify the contents of a. If you want to return a new array and leave the original alone, you can use collect instead of each:

# 1.8.7+:
a.collect &:compact

# 1.8.6:
a.collect {|s| s.compact}

Answer 2

If you were to use the in_groups_of you can pass it false as the second argument and it will not fill in the "blanks" with nil, but truly nothing.

Answer 3

Unless you want to permanently change a

a.map do |e|
  e.compact
end

Answer 4

arr_mixed=['hello', 2222, 'world', nil, [1, 2, 5, 'hi', nil],[1, 2, 3], [4,   5, nil]]

def compact_nested(array)
   arr2=[]
   array.each { |x|
   element = x.class==Array ? x.compact : x
   arr2<<element
   }
   arr2
end

p compact_nested(arr_mixed).compact #=>["hello", 2222, "world", [1, 2, 5, "hi"], [1, 2, 3], [4, 5]]
p arr_mixed #=>["hello", 2222, "world", nil, [1, 2, 5, "hi", nil], [1, 2, 3], [4, 5, nil]]

Answer 5

a.each {|subarray| subarray.compact!}
a.compact!

Should work....