Re: Fusion Laws?

On Thursday, March 31, 2016 at 2:45:43 PM UTC-5, Jason Orendorff wrote:
> On Thu, Mar 31, 2016 at 1:45 PM, Michael Haufe
>
> > Perhaps I'm misreading your statement here, but are you saying that the
> > current spec is hand-waving the runtime semantics of the language, or are
> > you instead saying that one can't formalize the semantics of a dynamic
> > language?
> 
> No and no. (The current spec is very detailed. The semantics of JS could
> certainly be formalized; I'm not sure you'd learn anything new though.)

Understood. Minor spec issues might be caught early, but from what I've seen in es-discuss, early implementations seem to do plenty well in catching these anyway. 

> I'm saying that the way JS programmers reason about their code---when we
> reason about it at all---hand-waves away all the complicating factors that
> JS engines are forced to treat seriously. We take for granted that many
> possible things that *could* theoretically happen, won't happen. We assume
> (rather than prove or propagate) a bunch of antecedents like "well, x and y
> are both gonna be numbers here, and neither one can be NaN, and this
> addition won't overflow, and this object won't be a proxy..."
> 
> JS implementations (and the spec itself) don't have that luxury.

Understood.