Ruby newbie here... I want to apply Array.map! to an element of a 2D array, but doing something like the example below applies map to every element of the array.
array = Array.new(3, Array.new(3, 0))
array[2].map! { |e| e + 1 }
print array
This gives me [[1, 1, 1], [1, 1, 1], [1, 1, 1]] whereas I want something more like [[0, 0, 0], [0, 0, 0], [1, 1, 1]].
You'll have to map each, for example:
modified = array.map{ |sub| sub.map{ |e| e+1 } }
If you want to mutate in-place:
array.each{ |sub| sub.map!{ |e| e+1 } }
However, you are not creating your initial 2D array correctly. You want:
array = Array.new(3){ Array.new(3) }
…so that the sub-entries are not shared. See the marked-as-duplicate answer in the comment above for more information.
Like @Phrogz said you just need to initialize correctly.
Then you can use your methodology
array = Array.new(3){ Array.new(3,0)}
#=> [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
array[2].map!{|e| e + 1}
#=> [1, 1, 1]
array
#=> [[0, 0, 0], [0, 0, 0], [1, 1, 1]]
