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lib/kitchen_sink/csv.ex
defmodule KitchenSink.CSV do
@moduledoc """
This module is for CSV helper functions.
"""
@doc """
transforms a sparse list into a new list of the same size with the sparse values filled in with the previous
non-sparse values.
## Example
iex> KitchenSink.CSV.fill([1,"","",2,"",3,""], "")
[1,1,1,2,2,3,3]
"""
def fill(sparse_list, empty_matcher) do
sparse_list_length = Enum.count(sparse_list)
{values, indices} =
sparse_list
|> Enum.with_index
|> Enum.reject(&match?({^empty_matcher, _}, &1))
|> Enum.unzip
indices
|> Enum.drop(1)
|> Enum.concat([sparse_list_length])
|> Enum.zip(indices)
|> Enum.map(fn {last, start} -> last - start end)
|> Enum.zip(values)
|> Enum.flat_map(fn {amount, value} -> List.duplicate(value, amount) end)
end
end