Trying to write good elixir code. Input: data = %{"a" => 0, "b" => 2, "c" => 0, "evilkey" => 666} for specific keys i need to write some specific output if condition is true Ruby version: out = [] out << "text1" if data["a"] > 0 out << "text2" if data["b"] > 0 out << "text3" if data["c"] > 0 ou…

Thanks! The solution with filters and map look about right. Re: IO.iodata_to_binary thing - i can’t just put things together this way, but overall it looks good, just need to add |> Enum.filter(fn(x) -> !is_nil(x) end), i.e. [ (if data["a"] > 0, do: "text1"), (if data["b"] > 0, do: "text2"),…

A more functional apporach output_texts = %{ "a" => "text1", "b" => "text2", "c" => "text3", } out = data |> Enum.filter(fn {_, v} -> v > 0 end) |> Enum.filter(fn {k, _} -> Enum.member(Map.keys(output_texts), k) end) |> Enum.map(fn {k, _} -> output_texts[k] end) |> En…

You can do that by using if as an expression and assembling list of values finally concatenating them together: IO.iodata_to_binary([ if(data["a"] > 0, do: "text1", else: ""), if(data["b"] > 0, do: "text2", else: ""), if(data["c"] > 0, do: "text3", else: "") ]) You could even extract the if …

data |> Enum.filter(&match?({_, v} when v > 0, &1)) |> Enum.map(fn {"a", _} -> "text1" {"b", _} -> "text2" {"c", _} -> "text3" end)

Also because nobody has mentioned this yet, the “ugly elixir version” is not actually an elixir version. It would not work at all because out is immutable.

It will, there are re-assignment for out: out = if ... out ++ ... else out end so every consequent out is different variable

We do not have any guarantee of ordering in a map. So in theory the begs pour of this snippet is non deterministic, while in the OPs version we do have an explicit ordering of the keys and their transformation/concatenation into the result.

I know people love |> but you don’t have to use it: :maps.fold(fn (k,v,acc) when v > 0 -> acc ++ [output_texts[k]] (_,_,acc) -> acc end, [], data) There is probably a function equivalent to fold in Enum but it is called something else and I could not immediately see it, …

Yeah, in my use-case ordering guarantees are required so maps don’t work (but for someone else it could be better approach). also there are other non-related keys as well (which should be filtered out) plain [..., ..., ...] |> remove nils works just fine - ordering granaries, short and easy to read…

Ah, classic name and not from the functional world. On a map there is no left or right.

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Writing idiomatic Elixir code

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NobbZ November 13, 2016, 7:02pm 11

It’s called reduce and is a left fold AFAIR