Question

Playing with Erlang, I’ve got a process-looping function like:

process_loop(...A long list of parameters here...) ->
    receive
        ...Message processing logic involving the function parameters...
    end,
    process_loop(...Same long list of parameters...)
end.

It looks quite ugly, so I tried a refactoring like that:

process_loop(...A long list of parameters...) ->
    Loop = fun() ->
        receive
            ...Message processing logic...
        end,
        Loop()
    end,
    Loop()
end.

But it turned out to be incorrect, as Loop variable is unbound inside the Loop function. So, I’ve arranged a workaround:

process_loop(...A long list of parameters...) ->
    Loop = fun(Next) ->
        receive
            ...Message processing logic...
        end,
        Next(Next)
    end,
    Loop(Loop)
end.

I have two questions:

1. Is there a way to achieve the idea of snippet #2, but without such “Next(Next)” workarounds?

2. Do snippets #1 and #3 differ significantly in terms of performance, or they’re equivalent?

Answer 1

1. No. Unfortunately anonymous function are just that. Anonymous, unless you give them a name.

2. Snippet #3 is a little bit more expensive. Given that you do pattern matching on messages in the body, I wouldn’t worry about it. Optimise for readability in this case. The difference is a very small constant factor.