no output should be "", <<"">> or undefined?

[Franklin Brauning]

maybe this is the wrong kind of optimization but on those typical cases like

 case Data of
  undefined -> WHAT SHOULD I EMIT HERE?
  _ -> Data
end

what should I return to waste the less of cpu cycles. I tend to use undefined becasue it
is very explicit but reading some defautl elements it emits no-output as ""

Also I have a not that related question: the WF_IF macros, or any erlang macro,
does it evaluate arguments in an eager fashion or lazy?

?WF_IF(false, 1, do_something())

will do_something() be evaluated ?

[Jesse Gumm]

This kind of optimization is so minimal as to be negligible.  Either <<>> or "" will be basically nothing in terms of processing speed.  The atom undefined should usually not be used in regards to an "emit" value if only because <<>> or "" says "emit an empty string", while 'undefined' being an atom is slightly semantically different: do you want to emit the text 'undefined' or do you want to emit an empty string?

As for ?WF_IF, it's lazy.  It's mostly an alias to case expression wrapped in a Fun (to prevent variable leaking), which means the raw case expressions will be slightly faster:

https://github.com/nitrogen/nitrogen_core/blob/master/include/wf.hrl#L136-L151

So with ?WF_IF(false, 1, do_something()),

do_something() will not be called.

-Jesse

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Jesse Gumm
Owner, Sigma Star Systems
414.940.4866 || sigma-star.com || @jessegumm