I wrote a a function that delete the content of database. Consider following code snipped: defmodule Seeds do def delete_db(values) when is_list(values) do cond do length(values) > 0 -> Repo.delete_all(values) true -> {:ok} end end end When I call the de…

[image] kostonstyle: My question is, do I follow functional specification? What exactly does that mean? It’s not technically a function, no, because it has a side-effect. The reality of Erlang & Elixir is that there can be side-effects in procedures anywhere. Pure functions in these languages…

You won’t really get pure functions that do operations on databse, files, environment variables etc. etc. the reason is that they interface with impure external environment. So I do not think there is anything wrong from that point of view in your code.

[image] gon782: Instead, pay attention to where you can do without them by passing data Can you show me please an example?

The essential quality of a “pure” function is that it always has the same output for the same inputs. You could make your function pure by passing in the state of the database and returning the state of the database, However, that’s not really practical. But you should strive to have anything you o…

Hey there. Your function is generally fine, but has a couple of style issues. First, it’d be clearer to use Enum.any? instead of lenght(values) > 0. Not only is this more readable, we don’t actually care what the length is, so long as there’s at least one item. No point in counting them all. Second…

Well, with refactoring in mind it might be better to simply do this: def delete_db([]) do :ok end def delete_db([_h | _t] = values) do Repo.delete_all(values) end It’s short, splits the procedure up into cases neatly and asserts structure at the same time.

As a final tweak, you can have the second clause just be def delete_db(values) because the only way it gets there is if it isn’t an empty list. You could add when is_list(values) if you really wanted to as well

[image] kostonstyle: Can you show me please an example? Think of it this way: If something needs updating, let’s say a map of some keys and values, you could conceivably have a process that guards that state and the way you interact with it is to send messages to that process in order to mod…

[image] benwilson512: As a final tweak, you can have the second clause just be def delete_db(values) because the only way it gets there is if it isn’t an empty list. You could add when is_list(values) if you really wanted to as well The possible issue is that you’re not necessarily asserting …