existential | The absolute minimum to enable authorization in Rails | Authorization library
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kandi X-RAY | existential Summary
The absolute minimum to handle custom fine grained authorization in Rails.
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- Check if the action is allowed for the resource .
- Check if the given existence .
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QUESTION
I hope this makes sense.
I'm trying to write a function that takes an object where each key equals a function and returns a function who's rest argument(s) are a translation of that object to [a key of the object, and the params of that key's function]
My Code: ...ANSWER
Answered 2022-Mar-15 at 02:28In what follows I'll call the operation in question, turning a key K (which extends keyof T for some suitable T whose values are all function types) into the tuple [K, ...Parameters], "parameterizing" K, or a "parameterization" of K.
Conceptually you want the return type of useConfig to be a function which accepts a variadic number of arguments, where each argument is a parameterization of some key in keyof T. You don't really want to know which argument is a parameterization of which key, just that each one corresponds to some key. This use of "some" is indeed a hint that the kind of generic quantification you'd need here is existential instead of the "normal" universal quantification. You can think of normal, universal generics as intersections over every acceptable type, while existential generics are unions over every acceptable type.
And here, since "every acceptable type" is just the single members of keyof T, then you can represent this union directly. All you want to do is distribute the parameterization operation over the union in K to make a new union.
If you want to distribute an operation over keylike types, you can use a distributive object type (as coined in microsoft/TypeScript#47109) where you make a mapped type and then immediately index into it. If you have a key set KS and you want to distribute the operation F over it, you can write that like {[K in KS]: F}[KS]. In your case KS is keyof T and F is [K, ...Parameters]. So you get this:
QUESTION
I want to narrow the type of a function argument based on a sibling property. I know that existential types would help but they are not available so I'm using a helper function. I currently have this thanks to jcalz in the comments
...ANSWER
Answered 2022-Feb-05 at 02:18You'd like helper() to treat the array literal value ["one", "two", "three"] as having the type ["one", "two", "three"]; that is, as a tuple of string literal types instead of as just string[]. This is easy enough to do from the caller's side of the function; callers can use a const assertion like ["one", "two", "three"] as const. But in cases where the callers don't want to (or cannot) use a const assertion, it would be nice to get the function itself to do it.
I opened microsoft/TypeScript#30680 a while ago asking for some easy way to do this. Maybe it would look like:
QUESTION
I get an error
...ANSWER
Answered 2022-Jan-26 at 03:08Here's a much smaller file that has essentially the same error:
QUESTION
So I am starting a chain with the intention that it
would have a fixed number of tokens, and the way I went about doing it is to configure one endowed_account: Alice with a set number of tokens in the genesis configuration. Alice so happens to also be the only validator, and she's also the only person running the node. When I create a try to send some tokens say 10 units from Alice to Bob, Bob gets the full amount, but total issuance goes down, presumably by the fees amount. Like if Alice initially had 100, and sent 10 to Bob, the total issuance in the block explorer shows something like 99.999 Units.
My intuition is that pub type TotalIssuance, I: 'static = ()> = StorageValue<_, T::Balance, ValueQuery>; calculates the sum of free and reserved balance of all accounts above existential deposit and then stores that value, which is why we don't see the "fees" being accounted for in it, and the "fees" is effectively burned. However this is my speculation and I am not sure. I would initially think of TotalIssuance as a hard upper limit on the number of tokens in circulation but is it so?
Besides this, I don't understand that since Alice is the only one validator and block producer in this chain, the fees should be going to her right, since typically block rewards go to the block producer? Yet, it's NOT so.
The second doubt I had regarding the transfer function is that the documentation says that if a transfer call puts the balance below existential deposit, the account will be "reaped". What does that mean? They've also provided an alternative transfer_keep_alive which quote:
works the same way as
transfer, but has an additional check that the transfer will not kill the origin account.
I am having trouble understanding these terms, since something I read previously said all valid pub/private key pairs are valid "accounts". So what does killing and reaping mean in this context?
...ANSWER
Answered 2022-Jan-10 at 11:10About the variations on the total supply I would recommend to read this entry about Imbalances, it directly tackle what you are asking for. https://crates.parity.io/frame_support/traits/tokens/imbalance/trait.Imbalance.html
As for the rewards if you are running just a simple dev network with no staking or nominations built in, I would say that is fair to assume that there will be no incentives for those running nodes. I can see that the more "basic" fee payment uses withdrawals. In the implementation for withdraw we can see that it returns an imbalance if successful, coming back to my first paragraph.
About existential deposit there is this very good writing about it already in the following FAQ page https://support.polkadot.network/support/solutions/articles/65000168651-what-is-the-existential-deposit- Hope it solves your doubts, if not I am happy to edit this response to add some info.
But I would like to add to that that the reaping only happens on one network at a time, meaning that if an account is reaped of a relay chain' state, it doesn't mean loosing the balances on other paras for that same key.
QUESTION
I am making a /quiz app and storing 100 questions and answers in a .json file but i only want 20 randomize questions to show.
I am getting an error "List index out of range"
How is this?
This is my code:
...ANSWER
Answered 2021-Dec-06 at 11:44The problem is that qno keeps incrementing past the length of the question_number array.
You need to do something like this:
QUESTION
In the example below, I'm wondering why funPoly can't accept the existentially quantified type value outersFromInnersEx, even though funEx can.
ANSWER
Answered 2021-Dec-02 at 02:36It's about type variances, you can make funPoly work by changing
QUESTION
I was trying to render graph in pdf generated using pdfkit. I found this solution https://quickchart.io/documentation/google-charts-image-server/#example
...ANSWER
Answered 2021-Nov-26 at 16:59I faced a similar issue a while ago, the thing here is that you have to consider that google charts is a library that is loaded when the page is rendered, meaning that in order to generate a pdf it should be already there before generating it. The approach you can use is to use a headless browser to emulate that the page is open and then the dependencies are loaded so when you send the HTML to pdfkit it will contain everything you need to generate the pdf or you can use selenium to do something similar. The tricky part however is to adjust the window size to hold all the charts, but you can sort it out with some trials.
QUESTION
edit: I have followed up with a more specific question. Thank you answerers here, and I think the followup question does a better job of explaining some confusion I introduced here.
TL;DR I'm struggling to get proofs of constraints into expressions, while using GADTs with existential constraints on the constructors. (that's a serious mouthful, sorry!)
I've distilled a problem down to the following. I have a simple GADT that represents points called X and function applications called F. The points X are constrained to be Objects.
ANSWER
Answered 2021-Nov-23 at 10:52I think the correct solution should look something like this:
QUESTION
In some cases it is easier to instantiate the one existential term before another. In this contrived example, I wish to set c = 3 first, and from that choose, say a = 1 and b = 2.
ANSWER
Answered 2021-Nov-18 at 10:48You can use that it is enough to prove that there exists c,b,a such that a+b=c.
QUESTION
I've been following along with this blog post, trying to understand how to emulate existentially quantified types using path-dependent types in Scala 3: https://dev.to/raquo/existential-crisis-implementing-mapk-in-scala-3-2fo1
And then I made the following example.
First we define monoids:
...ANSWER
Answered 2021-Sep-20 at 09:35It's because you have this implicit conversion
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