[eeps] allow external function as literals

[Richard A. O'Keefe]

On 3/10/2014, at 4:03 AM, Björn-Egil Dahlberg wrote:
> Is there any other potential literals that are needed. I don't think so, perhaps only solve this for fun exports and not the general case .. If it needs solving that is.

Just because a value *could* be explicitly written as
a literal doesn't mean it is *easy* to do so.

Don't make the mistake of thinking that "is a literal" and
"is evaluated only once" are the same.  They aren't.
Suppose you want to have a list of references that is
going to be requested often.

You cannot write a reference as a literal at all.
You *can* fake it by doing

B = term_to_binary([make_ref() || I <- lists:seq(1, 100)])

then pasting that into the skeleton

refs() -> binary_to_term(
  % paste here
).

But it would be better if you could write

-once.
refs() ->
    [make_ref() || I <- lists:seq(1, 100)].

I note that if something is a literal in Erlang I can use
it in a pattern.  This is not true of fun mod:name/arity.
With the patch we are discussing to make these things that
can be stored at load time, they still are not *LITERALS*.

Think of the possibilities of tree-structured sets and
dictionaries; you *can* break encapsulation and write those
as explicit ground terms, but you would be mad to do so.
Personally, I've wanted to do that several times.