Arc Forumnew | comments | leaders | submitlogin
2 points by rocketnia 2517 days ago | link | parent

I hope it's useful to you. The R-1RK is pretty well-reasoned in most regards, so it's some good inspiration. ^_^

...But I can't leave well enough alone. Here are a few key places I disagree with the philosophical choices:

"G3: Dangerous [things] should be impossible to program by accident" is pretty bogus, and even if I give it the benefit of the doubt, it's poorly phrased. IMO, things should be made purposefully difficult only when that makes the useful things easier overall. I think most uses of G3 in Kernel are actually efficiency concerns

"G2: The language primitives should be capable of implementing all the advanced features of R5RS" is a bit scary. I can't say I don't do the same sort of thing by making Penknife a similar experience to Arc, but I suspect heavy inspiration from a single souce is usually more of a bias than a productive motivation. It'd be best to justify each "advanced feature" on its own merit and to be ready to take inspiration from lots of sources. But hey, if someone has have enough time on their hands to do a point-by-point restoration of another good system, or if they don't have enough time to weigh the options, it's a reasonable pursuit. (Maybe. ^^; How much of that is me telling myself that? 'Cause somehow I feel I fall into both the "enough time" and "not enough time" cases, and it sounds a bit like I'm looking for excuses. :-p )

But most importantly, I think "G1a: [All] should be first-class objects" is better served by making every primitive utility's domain explicit and extensible. That is, reducing the number of official ways to contrast the first-class-ness of particular objects. To be fair, Kernel puts a strong emphasis on supporting cyclic data structures, and that's one big case which extensible utilities probably need to plan for in advance (so that extensions aren't limited to being naive recursive traversals). But on the other hand, Kernel's 'equal? doesn't allow a programmer-defined type (an encapsulation) to provide custom behavior, so it actually makes those types second-class. @_@



1 point by evanrmurphy 2516 days ago | link

> "G3: Dangerous [things] should be impossible to program by accident" is pretty bogus, and even if I give it the benefit of the doubt, it's poorly phrased.

The paper actually says, "Dangerous things should be difficult to do by accident" [1]. I don't mean to nitpick, but in this context I think the difference between "difficult" and "impossible" is significant.

Update: I just realized that Shutt's dissertation and the R-1RK are distinct, but the quote is consistent across them.

---

[1] From page 88 of jshutt.pdf, downloadable at http://www.wpi.edu/Pubs/ETD/Available/etd-090110-124904/

-----

2 points by rocketnia 2516 days ago | link

That difference is significant too, but I'm specifically talking about the difference between trying to make something difficult and neglecting to make it easy. I pick a tool in the first place because it lets me do things more easily.

...Oh, I misquoted it. XD Yeah, thanks for catching that.

Another thing I missed was finishing the efficiency sentence. I was going to devote another paragraph to criticizing the efficiency-should-only-arise-naturally rule for being hypocritical--that an eye to efficiency influences and probably compromises other aspects of the design from the outset--but I determined I actually agree with that rule for Kernel. I think efficiency of fexprs is one of the most significant things Kernel stands to prove, so I don't mind an explicit and upfront goal of efficiency, but efficiency isn't in itself a goal motivating Kernel (I think), so it's good for the rule to be nuanced a bit. (Had I completed the sentence, it would have covered some part of that, but I'm not sure which. XD )

-----

1 point by rocketnia 2516 days ago | link

Oh, that dissertation is new(-ish)! Last time I looked into Kernel it was just the R-1RK. Gotta read that sometime. ^_^

-----