This is a question that originated on the Elixir Slack from David Billskog and I have made only minor changes to the module. Given this module: defmodule Dummy do def execute(x) do with var_a <- get_a(x), var_b <- get_b(x) do IO.inspect(var_a, label: "a") IO.inspect(var_…

Thanks for the isolated case. I was able to convert it to Erlang: -module(dummy). -compile([no_auto_import]). -export([execute/1]). execute(_x@1) -> _a@1 = get_a(_x@1), _b@1 = get_b(_x@1), erlang:display(_b@1), case _a@1 /= _b@1 of false -> nil; true ->…

I tested this with elixir 1.11.0 and Erlang 23.1 and I get a different result: get a get b a: 3 b: 2 {3, 2} a: 3 b: 2 {3, 2}

You probably need parenthesis around the if statement for the "returning a" part. defp get_a(x) do IO.puts("get a") (if Enum.any?(x, & &1 == "A"), do: 3, else: 2) |> IO.inspect(label: "returning a") end But I’m not sure what happens with the output, seems strange that var_b change …

@axelson my hunch is that you are running into an Erlang or Elixir bug. Update to Erlang 23.1 and see if it persists. :slight_smile:

I just tried 23.1 (and 1.11.2) and can still reproduce the issue from slack. @axelson ’s example doesn’t seem to cause issues for me. ❯❯❯❯ asdf local erlang 23.1 ~/Temp/test_elixir_problem ❯❯❯❯ iex …

Ah, yes you are correct about the reason the inspects are not printing out (I forgot about the precedence rules with |>).

We can check how the code was developed by using quote do quote do if Enum.any?(x, & &1 == "A"), do: 3, else: 2 |> IO.inspect(label: "returning a") end |> Macro.to_string() |> IO.puts() That results to if(Enum.any?(x, &(&1 == "A"))) do 3 else 2 |> IO.inspect(label: "returning a") end Whi…

Can confirm - Axelson’s example works fine on my machine (OTP23.1 / Elixir 1.11.2) and this one fails. A colleague tried @LostKobrakai ’s example on 22.2.6 / 1.11.1 and it printed 2 three times, as expected…

Poked at it a little more. Strange things are afoot - I get different results depending on what’s on a line that never executes (OTP 23.1 / Elixir 1.11.2): defmodule Dummy do def execute(x) do with var_a <- get_a(x), var_b <- get_b(x) do IO.inspect(var_a, label: "a") IO.i…

I simplified the example to this and can still reproduce the odd print running macOS Catalina 10.15.7 using Elixir 1.11.2 and Erlang 23.1.5. defmodule Dummy do def execute(x) do with a <- get_a(x), b <- get_b(x) do IO.inspect(b) if a != b do IO.inspect(b) end end…

Elixir Programming Language Forum

Weird/incorrect output from a with statement

Questions & Help Questions

axelson December 9, 2020, 8:41pm 7

I’m still seeing the issue with elixir 1.11.2-otp-23 and erlang 23.1.5