Is Enum.reduce the "best fitting Enum function" for total_quantity in `boutique-inventory`?

[mikegehard]

Solution Implementation:

def total_quantity(item) do
   Map.values(item.quantity_by_size)
   |> Enum.sum()
end

The solution says:

I agree that reduce is a good function/concept to practice with for this solution but "best fitting" seems like a stretch. It took me a long time to understand the concept of reduce when learning functional programming and this may be a head scratcher for some folks new to Elixir and functional programming togther.

Would it be possible to change that message to say "Use the Enum.reduce function in the total_quantity function to practice."?

This doesn't give folks who can't figure out reduce right away the feeling like they are doing it "wrong".

[DillonReddingStord]

While not as clear as your solution with Map.values/1 and Enum.sum/1, here's another alternative to Enum.reduce/3:

def total_quantity(item) do
   Enum.sum_by(item.quantity_by_size, &elem(&1, 1))
end

[RobertDober]

@mikegehard No Enum.sum_by is the correct tool (see above)
a compromise between readable and concise might look like

...
|> Enum.sum_by(fn {_, qty} -> qty end)