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1 point by rocketnia 2264 days ago | link | parent

I mostly followed along, but I don't understand "It will work in my system as well, because undefined symbols automatically create new boxes." You were talking about having them create new boxes at assignment time, and I was recommending compiling-a-reference-time instead so that we don't get an unbound variable error in the first definition.


1 point by Pauan 2264 days ago | link

How it works is, anytime the compiler sees an undefined symbol, it creates a new box for it like as if it had been created with "var".

Another way to think about it is... the compiler would replace this:

  (= foo (fn () ... bar ...))
  (= bar (fn () ... foo ...))
With this:

  (var bar)
  (var foo)
  (= foo (fn () ... bar ...))
  (= bar (fn () ... foo ...))
What happened is, when it encountered the undefined variable "bar", it created a new box for it. Then it encountered the undefined variable "foo", so it created a new box for it. Then it did the assignments like normal.

Given how you said "compiling-a-reference-time", I think we're talking about the same thing. Why did you mention assignment time?

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3 points by rocketnia 2263 days ago | link

"Why did you mention assignment time?"

We've just had a long exchange about you creating boxes at assignment time and me using compiling-a-reference time instead. Here's a recap:

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You: Here's how you do it. The definition of "=" is the same: if the variable exists, mutate it, otherwise create a new variable. But now you add in a new primitive called "var"[...]

Me: The behavior I'd use is that any compile-time variable access (even under a lambda) creates a new, uninitialized variable binding if a binding doesn't already exist.

You: Yeah I'd do that too, if I wanted to graft dynamic variables onto a hyper-static system. But since Arc uses dynamic variables, I proposed to graft hyper-static onto it instead.

Me: How do you make the even/odd code work? Under the approach you described, the first line refers to an undefined variable (odd), and I interpret that as an error. I was recommending a fix.

You: Easy: I have a macro called "defs" that handles mutual recursion

Me: While I appreciate 'defs, it's a non-answer. The even/odd example [...] should work without modification.

You: It will work in my system as well, because undefined symbols automatically create new boxes.

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At least we seem to be agreeing now. ^_^;

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3 points by Pauan 2263 days ago | link

Ah, sorry, huge miscommunication and misunderstanding on my part. I've actually been agreeing with you all along.

A large part of the problem is that I've been thinking about my proposal as two separate parts: one part deals with backwards compat with Arc, and the other part describes a hyper-static system for Arc.

When I was talking about "defs", I was talking about the hyper-static part. But you were talking about the backwards compat part. Hilarity (?) ensues.

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1 point by rocketnia 2263 days ago | link

Okay, we're on the same page now then. ^_^

Having both kinds of scope as options would be great.

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