generics | Experiments with Go generics | Functional Programming library
kandi X-RAY | generics Summary
kandi X-RAY | generics Summary
Quick experiments with Go generics. This is really nice. It addresses the main things I miss about generics, namely. and does so without overwhelming complexity. By comparison, C++'s templates are extremely powerful, but syntactically and semantically quite complex, and historically the error messages have been both confusing and too late. (Templates also lead to considerable bloat in the text segment, but that may be a risk of the Go approach too.) Java's generics are limited to reference types, and thus are no use for efficient algorithms on (say) arrays of integers. Somehow the Go approach seems to do most of what I need while still feeling simple and easy to use. Users will no doubt build generic libraries of collections, of stream processing functions, and of numeric analysis routines. The design space for each is large, and I imagine arriving at simple, efficient, and coherent APIs worthy of the standard library will be an arduous task. But there is no need to hurry. My experiments have tended to parameterize over built-in types, or "any". I should probably spend more time investigating interface-constrained types.
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QUESTION
I'm having trouble understanding why TypeScript is inferring a certain type for an array element when the type is a union type and the types 'overlap'. I've reduced it to this minimum repro:
...ANSWER
Answered 2021-Jun-15 at 19:42See microsoft/TypeScript#43667 for a canonical answer. This is a design limitation of TypeScript.
As you might be aware: in TypeScript's structural type system, Child
is a subtype of Base
even though it is not explicitly declared as such. So every value of type Child
is also a value of type Base
(although not vice-versa). That means Child | Base
is equivalent to Base
... although the compiler is not always aggressive about reducing the former to the latter. (Compare this to the behavior with something like "foo" | string
, which is always immediately reduced to string
by the compiler.)
Subtype reduction is often desirable, but there are some places where Child | Base
's behavior is observably different from Base
's, such as excess property checks, IntelliSense hinting, or the sort of unsound type guarding that happens with the in
operator. You haven't shown why it matters to you that you are getting a Base
as opposed to a Child | Base
, but presumably it's one of these observable differences or something like it.
My advice here is first to think carefully about whether or not you really need this distinction. If so, then you might consider preventing Base
from being a subtype of Child
, possibly by adding an optional property to it:
QUESTION
I'm trying to create a few generic recursive types to modify structure of existing types. I can't tell why the sections inferring arrays and nested objects is not getting triggered. Any idea what I'm doing wrong?
TS playround link with the below code:
...ANSWER
Answered 2021-Jun-15 at 00:56Assuming what I mentioned in my comment on your question, the fix is just to simplify your FieldWithConfidence
type significantly. Right now it is trying to add a number of additional levels of structure beyond what you seem to want. Here is a version of that type that works as I think you intend:
QUESTION
I was looking at the Microsoft Rust guide and while reading the generics chapters, I came across the following problem.
Consider the two following pieces of code:
...ANSWER
Answered 2021-Jun-14 at 12:47In the first case:
QUESTION
I have the following code to which I tried to apply generics.
...ANSWER
Answered 2021-Jun-13 at 10:57You need to do things slightly different when you're defining a struct, and when you're instantiating a struct.
When you write:
QUESTION
i know this convention of generics
E - Element (used extensively by the Java Collections Framework)
K - Key
N - Number
T - Type
V - Value
S,U,V etc. - 2nd, 3rd, 4th types
But i don't know it when I named service of generics in spring
For example,this abstract class is used when Datas do select, insert, update, delete in controller
i want to name B body of reqeust and RB to name body of response Is it okay?
Can you Recommend me generics name which is used in service of controller ?
ANSWER
Answered 2021-Jun-13 at 06:58If you want to go strictly by the book and the common convention, you may go for below. Note in your writeup you have already mentioned that T should be used for Type and S for Second Type etc..
public abstract class AbstractService
However, if you want to make it more explicit and avoid any possible confusion with Second Types etc.., you could use convention like below which explains the context of usage as well.
public abstract class AbstractService
Optionally, you may also want to make these look like classes to depict more specific inputs, and go for something like below.
public abstract class AbstractService
All options would work, but its usually driven by the convention being followed in your project/enterprise. First one is probably what you are looking for here.
Please note, while Java will not be unhappy with 2nd and 3rd options mentioned here, if you are a stickler for Code Quality and Static Analysis, Sonar will be unhappy with using such names. It expects you to use either S, T convention, or you may also choose T1, T2 to indicate the two types.
public abstract class AbstractService
Between S, T and T1, T2, you should probably go for the S, T convention. Sonar expects type names to follow the pattern '^[A-Z][0-9]?$'
Hope this helps you decide. If you are confused with options, you can simply go with the 1st one.
QUESTION
Assume that
...ANSWER
Answered 2021-Jun-13 at 04:21Think of the parameter as a constructor instead of a class:
QUESTION
Here's a simplified code of what I am doing:
I have this custom ViewHolder
:
ANSWER
Answered 2021-Jun-13 at 02:29Due to type erasure, you cannot do this without passing the concrete class to the constructor. Or, to avoid having to use reflection to find and call the constructor, it would be cleaner to give the constructor a function parameter for constructing the ViewHolder, so you can just pass the a constructor reference.
Example:
QUESTION
I have a custom User model with a blocked
field as
ANSWER
Answered 2021-Jun-11 at 21:16You can use SerializerMethodField and calculate it. Get the authenticated user and check if the serialized user is in the blocked list.
QUESTION
When I go to this http://127.0.0.1:8000/api/questions/ I get
urls.pyTypeError at /api/questions/
'list' object is not callable
(in project)
...ANSWER
Answered 2021-Jun-09 at 06:44The DEFAULT_PAGINATION_CLASS
setting should be a string not a tuple/list
QUESTION
I am learning how to use const generics in rust. An easy demo like this: Playground
Can somebody tell me how to use a const generic array as a return type?
...ANSWER
Answered 2021-Jun-09 at 02:56The point of const generics is that the size of the array is known at compile-time. If you want a runtime-known size, then that's what Vec
is for. Consider
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