Secretargs happen to be implemented in terms of dynamic boxes. The benefit of secretargs is that you can always pass the default value just by making a normal function call; you don't risk propagating the existing dynamic value into the call. Whether that's important in this case is up to you. ^_^
Oh, and I don't think we can say anything's standardized in Arc at all. :-p The standards are just implicit assumptions around these parts.
Note: when I said "standardized" I meant in the "de facto standard" way. Arc has plenty of those. :P
I agree that Arc has essentially no de jure standards[1], and I think that's a good thing.
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* [1] The closest thing would probably be whatever pg does, but that would only concern the question of what official Arc is; other implementations would be free to either follow official Arc, or branch off into a different Arc-like dialect.
