is
compare?/2a macro?
Yep! Its purpose is so that you can write:
compare?(a < b, Date)
And it gets translated to the correct:
Date.compare(a, b) == :lt
You can read more here: CompareChain - Semantic, chained comparisons for Elixir
but as José said you want the operator out of the call, like this:
Process.get(:not_a_key, a) < b.
Thanks, I was skimming and missed this point. But it didn’t work either 
