Yes, I fully agree with that, and it answers Thad's questions to me better than I could.

The other thing is that I actually don't think looking up a ZObject is free. The evaluation implementation can basically pass everything that is not a Z7 unchanged on, so no look ups are needed. And that's not only true for the top level of the input, but for every subsequent level and also for every inner evaluation step.

So having an explicit Z7 marker saying "this needs to be evaluated" can speed things up considerably.

Thanks for the thoughts, it helped me quite a bit!

On Sun, Oct 18, 2020 at 8:33 PM Subramanya Sastry <ssastry@wikimedia.org> wrote:

In general, it seems better to use explicit typing (via a Z7 object to indicate something is a function call) vs. implicit typing (if Z1K1 is a function call, then this is a function call).

It might potentially lead to simpler error semantics. What if a typo / accidental keystroke changes "Z142" to "Z12" and Z12 were not a function? Then, suddenly the behavior of wherever this object was used would change mysteriously .. in some cases, it might error immediately (because of the context), and in other cases, it might fail downstream and in other cases, it may lead to incorrect output.

With an explicit Z7 type, there is no scope for such confusion and you get immediate failure (assuming validation is enabled) on typos / errors.

Subbu.

On 10/15/20 6:12 PM, Denny Vrandečić wrote:
So just thinking out loud.

I was thinking about that too - do we even need the Z7?

The advantage of having an explicit Z7 is that we know immediately that this is an object that needs to be treated specially. On the other side, that seems to be only one removed - we just need to look up the type of Z142, and if it is Function, well, there we are!

The other advantage of using an explicit Z7 is that we could use a Z142 without a Z7 embedding it like a quote in lisp. The Z7 unquotes and evaluates it.

So not sure if Z7 is needed. I would love to hear more thoughts. I have the sense that it would be really useful to keep the Z7, but I have trouble to say exactly why.




Regarding the Currying: that should not be a problem either way, though, if I understand right. So assume that we have a function curry Z78 and the concatenate function Z142.

Z1K1:
  Z1K1: Z7
  Z7K1:
    Z1K1: Z78
    Z78K1: Z142
    Z78K2: "Wiki"
K1: "data"

So here we use curry(concatenate, "Wiki"), which results in a function that takes a single string and prepends "Wiki" to it, so that would be read as curry(concatenate, "Wiki")("data")

Note that the K1 would need to be a local key as there is no global key that could be used, as the function is being created on the fly.

But please correct me if I misunderstood your comment on currying.



Thanks so much for your thoughts!

On Thu, Oct 15, 2020 at 5:34 AM Arthur Smith <arthurpsmith@gmail.com> wrote:
Hi Denny - this is interesting, but perhaps it means we don't even need the Z7 type at all? That is, just go with:

Z1K1: Z142
Z142K1: "Wiki"
Z142K2: "data"

So every instance of Z8 (function type) is itself a type whose instances are function calls? I'm wondering how either approach would allow for currying though... I guess that gets into function implementations? But at some level you'd want a function call that allowed for combining both Z142 keys and the key of the curried function. So there may still be a need for several different key prefixes within the same ZObject?

   Arthur

On Wed, Oct 14, 2020 at 7:16 PM Denny Vrandečić <dvrandecic@wikimedia.org> wrote:
This is a rather technical question. If you are not interested in the inner working of the function model, feel free to safely skip this one.

Currently, a function call is represented as follows (assume, Z142 is the concatenation function):
Z1K1: Z7
Z7K1: Z144
Z144K1: "Wiki"
Z144K2: "data"

If we use global keys, it would look like this:
Z1K1: Z7
Z7K1: Z144
K1: "Wiki"
K2: "data"

The local keys in this case get expanded against the Z7K1 value, not the Z1K1 value, as is the case for all other local keys. This makes it very different than all the other objects, and requires special handling.

The suggestion is to change the representation of function calls and make them more unified compared to the other entries, i.e. like this:

Z1K1: Z7
Z7K1:
  Z1K1: Z144
  Z144K1: "Wiki"
  Z144K2: "data"

So, instead of pulling the values into the Z7 object, we basically instantiate a function just like any other type, and wrap it into a Z7 to say that this is a function call. This needs one extra object, but it leads to much more uniform handling of objects.

Any thoughts?

Cheers,
Denny
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