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Are "jets" a good idea?I've noticed the beginning of a trend in hobbyist/amateur programming language theory. There have been a number of recent programming languages that have extremely minimalistic semantics, to the point of being anemic. These languages typically define function types, product types, the unit type, perhaps natural numbers, and not much else. These languages are typically capable of universal computation, but executing programs in them directly would be comically slow, and so what they do is recognize special strings of code and replace them with implementations written in a faster meta-language. This pair of the recognized string of code and the efficient replacement is known as a "jet", or an "accelerator". Some languages that do this:
My question is this: is this idea of "jets" or "accelerators" a serious approach to programming language implementation? There's an obvious question that comes to mind: how do you know the object language program and the meta-language program you've replaced it with are equivalent? Simplicity claims to have done a number of Coq proofs of equivalence, but I can't imagine that being sustainable given the difficulty of theorem proving and the small number of developers able to write such a proof. Urbit takes a rather cavalier attitude towards jet equivalence by advocating testing and simply treating the jet as the ground truth in the case of a conflict. And I know David posts here so I hope he will respond with Awelon's take on this matter. Here is an excerpt from the Simplicity document arguing in favor of jets:
In the interest of charity, I'll also try to make an argument in favor of this approach, although I remain skeptical: an extremely minimal programming language semantics means a language designer can truly consider their work to be done at some point, with no further room for improvement. A minimalistic Python would have largely avoided the fiasco involved in the upgrade from Python 2 to Python 3, by pushing all of the breaking changes to the library level, and allowing for more gradual adoption. Languages features added to JavaScript in recent years (like classes, async/await, modules and so on) would also have been libraries and presentation layer additions instead of breaking changes at the implementation level. By xkapastel at 2017-11-03 03:23 | LtU Forum | previous forum topic | next forum topic | other blogs | 37734 reads
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