On May 31, 2012, at 5:18 PM, Mark S. Miller wrote: > On Thu, May 31, 2012 at 4:44 PM, Allen Wirfs-Brock <[email protected]> > wrote: > > I don't think I argued that for isBound although I certainly would make that > argument about arrow functions in general. > > In this case, I'm assuming a debugging scenario. Somebody is passing arrow > functions through an API whose contract requires a callback function that is > invokable with a dynamic this. I'm trying to find the culprit. So I write a > function like the above to try to catch it. Or I just put a isBound check in > the API function. > > It's true, that an offending function might be one that was written with a > dynamic this binding but which never actually references this. That is also > probably a violation of my contract. So, I may get false negative. But there > is still a good change that finding positives will solve my debugging problem. > > Thanks for the clarification; I'm not sure I would have guessed that from > this code. > > For the purpose you state, given two isBoundOrWhateverItIsNamed functions f > and g where, > > * neither has any false positives, > * both obey simple deterministic rules that are easy to understand, > * f has strictly fewer false negatives than g. > > Which should you prefer for the purpose of your code? > If I understood it, I would probably prefer what you are proposing. However, I suspect that many JS programs will conceptually equate "bond this" with bound functions and arrow functions and not think about equating it with the concept of "has no dynamic this dependencies". The rules for the later not so simple given that they need to include strict mode and eval conditionals.
Allen > > -- > Cheers, > --MarkM
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