why are zero arity anonymous functions not allowed?

[Scott Parish]

It seems inconsistent that the anonymous function sugar is not allowed for zero arity functions. Is there a good reason for this, or did this need to be proposed as a feature request instead of a bug?

Reference: https://github.com/elixir-lang/elixir/issues/5042

Thanks

[Ben Wilson]

The title is a bit misleading as it implies that Elixir doesn't have `fn -> "yo" end`, but at least that's cleared up in the body.

I do think it can be useful, IE `Task.async(&foo(args))` is more succinct than `Task.async(fn -> foo(args) end)`. Spawning processes and the like are about the only cases I can think of where zero arity functions are used frequently, but it does seem like it would be a win for consistency and readability in certain cases.

Perhaps there are ambiguities introduced however without &1 and friends? I'm sure one of the core team members will clarify.

[Scott Parish]

Another one is: :timer.tc(&mycode(args))

Or the case where this originally came up today: retry_num_times(10, &fn_that_may_not_succeed_immediately!(args))

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[Scott Parish]

Thanks for the details! Makes a lot more sense now.

On Wed, Sep 7, 2016 at 11:58 AM, <cristi...@surhive.com> wrote:

According to https://groups.google.com/forum/#!topic/elixir-lang-core/GeXNvzzmdps, it seems that if you allow zero arity with & there is an ambiguity when parsing the expressions.
&fun/2 could be parsed as (fn -> fun end) / 2 or fn(x,y) -> fun(x,y) end

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