Recent questions tagged Generics

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generics - Is it possible in Scala to force the caller to specify a type parameter for a polymorphic method?

//API class Node class Person extends Node object Finder { def find[T <: Node](name: String): T = doFind(name). ... <:< for this :-) Ideas ? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - in Java syntax, Class<? extends Something>

Class<? extends Something> Here's my interpretation, it's class template but the class ? means the name of ... my interpretation, let me know. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - java: HashMap<String, int> not working

HashMap<String, int> doesn't seem to work but HashMap<String, Integer> does work. Any ideas why? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - How do I combine multiple functions using Diesel into one through abstraction?

I have the following two functions: pub fn get_most_recent_eth_entry(conn: &SqliteConnection) -> Result<i32, Error> ... ::bitcoin::table` See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - Java unchecked conversion

I have the following line of code this.htmlSpecialChars = this.getSpecialCharMap(); where private HashMap<String,String ... I stop this warning? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - Is there a difference between explicitly putting the type into the diamond operator vs letting java figure it out?

Is there any difference between initialization via: MyWrapper<String> wrapper = new MyWrapper<String>(); vs ... write it that way. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - The size for values of type `T` cannot be known at compilation time when using mem::size_of::<T> as an array length

Consider the following function: fn make_array<T>() where T: Sized, { let bytes = [0u8; std::mem::size_of::<T> ... and how do I work around it? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - C#'s can't make `notnull` type nullable

I'm trying to create a type similar to Rust's Result or Haskell's Either and I've got this far: ... 3 with nullable reference types enabled. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - Wrong number of type arguments: expected 1 but found 0

I'm trying to pass a reference of std::io::BufReader to a function: use std::{fs::File, io::BufReader} ... type argument What am I missing here? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - Java: How to set a default for "T" in SomeClass<T>?

Is there a way to specify a default type for a generic template? Let's say I have a Monkey class. ... without having to explicitly suppress it? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - C# Reflection - How can I tell if object o is of type KeyValuePair and then cast it?

I'm currently trying to write a Dump() method from LinqPad equivalent iin C# for my own amusment. I'm moving from Java ... o) { ... } Thanks! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - How covariant method overriding is implemented using bridging Technique in java

While reading on Covariant Overriding, i find out very strange fact, covariant method overriding is implemented using ... help me with example. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - Why are stateful widgets defined as two classes in flutter?

I'm new to flutter/dart, so while I try to make an app I also try to understand why things are a ... StatefulWidget class but not quite sure. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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603 views

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generics - C# List<object>.RemoveAll() - How to remove a subset of the list?

I have a 2 classes feeds_Auto and Product with multiple matching properties. For this particular problem, the AutoID is ... item in each pass. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - How do I return an instance of an object of the same type as the class passed in using Java 6?

I want to return an instance of an object of same type of the Class object passed in. The type passed ... = (MyClass)getObject(MyClass.class); See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - Java name clash, have the same erasure, neither hides the other

I am getting this name clash error and i don't know how should i solve the problem. I have two classes and i am ... ()); } return sensors; } } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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592 views

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generics - How do I setup multiple ORed type bounds in Scala

Is it possible to do something like this in Scala: class MyTest { def foo[A <: String _or_ A <: Int] ... this possible? (Similar question here) See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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612 views

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generics - Java 8 and Generalized Target-Type Inference

I have installed the last JDK 8 ea b114 to test the new language features. However the inference in chained ... calls will not be inserted? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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generics - What is Vec<_>?

I have seen Vec<_> a couple of times already. For example: let a = "line1 line2 line3"; println!("{:?}" ... as a name for an unused variable. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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396 views

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generics - C# Casting a List<ObjBase> as List<Obj>

Why can I not cast a List<ObjBase> as List<Obj>? Why does the following not work: internal class ObjBase { ... , or null type conversion Thanks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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557 views

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generics - Java thenComparing wildcard signature

Why does the declaration look like this: default <U extends Comparable<? super U>> Comparator<T> thenComparing( Function ... U> all the same? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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650 views

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generics - StringDictionary vs Dictionary<string, string>

Does anyone have any idea what the practical differences are between the System.Collections.Specialized.StringDictionary ... over the other? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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543 views

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generics - How to use Java reflection to check a given class is implements Iterable<? extends T>, for any given T

I have a specific target type (decided at runtime), and an iterable class that I'm comparing ... extends Iterable<SomeObject>) See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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563 views

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generics - C# virtual static method

Why is static virtual impossible? Is C# dependent or just don't have any sense in the OO world? I know ... answer to the previous question. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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790 views

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generics - In Swift, how to cast to protocol with associated type?

In the following code, I want to test if x is a SpecialController. If it is, I want to get the ... SpecialController { // does not compile See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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555 views

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generics - Difference between ? (wildcard) and Type Parameter in Java

Can somebody explain me what the difference is between these two methods? Are they same? They do look same to me ... ; System.out.println(); } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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442 views

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generics - What is memoization good for and is it really all that helpful?

There are a few automatic memoization libraries available on the internet for various different languages; but ... especially appreciated here. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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530 views

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generics - Java class with concrete type as parameter

Is there any point in declaring a class with "concrete" types as generics? If yes, what's the use for it? ... " the generics. Thanks in advance. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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