[erlang-questions] Best way to test if empty dict/set/etc.?

Rapsey rapsey@REDACTED
Fri May 31 08:31:38 CEST 2013

Check the implementation of those data structures. There is always a
function that could tell you if it is empty or not. If size would not
be a O(1) call, it would probably say calc_size or something.
dict:size is O(1).

On Fri, May 31, 2013 at 12:17 AM, Jonathan Leivent <jleivent@REDACTED> wrote:
> I noticed that a lot of the opaque data structures don't have an is_empty
> predicate.  What is the best way to test if one of these is empty?
> Preferably an O(1) test, not size(X)==0 (unless that is O(1)), because the
> structure might be quite large.
> One way I thought of is to use fold on a function that just throws:
>   is_empty(Dict) ->
>     catch dict:fold(fun (_,_) -> throw(false) end, true, Dict).
> But that is disturbingly ugly.  Is there a preferred way to do this?
> Thanks.
> Jonathan Leivent
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