Recent questions tagged Generics

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generics - Why do I get "missing lifetime specifier" or "wrong number of type arguments" when implementing a trait for a struct?

I'm trying to define and implement a trait for a struct. All my implementations with generics and lifetime have ... ^^ expected 1 type argument See Question&Answers more detail:os...

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

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857 views

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generics - Java override Object equals() method

How do I override the equals method in the object class? i.e I have class Person{ //need to override here public ... (Person) obj it won't work. 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 syntax <T extends Class<T>> in Java

I have couple of thoughts regarding the following: public interface MaxStack<T extends Comparable <T>> 1-Why ... both extend from Comparable. 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 is it that ArrayList works with COM Interop, but IList<T> doesn't?

I've noticed that if I make a .NET component that exposes an ArrayList, then that ArrayList passes through ... Interop to a scripting engine? 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 override constructor using List<CustomObjects> - "same erasure" error

Hi I want to override constructor in custom class MyList. Code below can be compiled, I receive "same erasure" error. For ... ) { type = 2; } } 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 - Store Encodables in a Swift Dictionary

I'm looking to store models objects in a Dictionary and would like to serialize the whole dictionary using JSONEncoder ... ? What am I missing? 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, what does it mean when a type is followed by angle brackets (as in List<Foo>)?

I saw sometimes a type object inside <> beside of another object type declaration. For instance: NavigableMap< ... me an easy explication? 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 can I enforce equality of two associated type parameters of traits?

I have a function f which takes two arguments of the same type, and a function g which takes two arguments of ... of g to make it work? See Question&Answers more detail:os...

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

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744 views

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generics - Is there a way to determine the signature of a Lua function?

Recently, Lee Baldwin showed how to write a generic, variable argument memoize function. I thought it would ... two separate memoize functions. 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 does Map<?, ?> mean in Java?

What does Map<?, ?> mean in Java? I've looked online but can't seem to find any articles on it. edit : I found this on MP3 Duration Java See Question&Answers more detail:os...

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

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614 views

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generics - Why does the diamond operator not work for java.util.Collections methods in Java 7?

In Java 1.7.0_55, if I write this field declaration, I get a compilation error ("incompatible types"): private ... Can anyone point me to 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 - Typescript equivalent of ? unknown wildcard

Say I want to declare an array of generics in Typescript. What would be the equivalent of the unknown wildcard ... when it is declared. Cheers. See Question&Answers more detail:os...

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

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771 views

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generics - Java Type Erasure: Rules of cast insertion?

The Java tutorial on type erasure doesn't seem to detail the specific rules of cast insertion by the compiler. ... type chosen for the cast? See Question&Answers more detail:os...

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

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581 views

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generics - Generified implementation of Visitor pattern in Java

I've made some research trying to develop a type conversion framework which provides an ability to convert instances of a ... 's converted from an instance of Foo"); } @Overrid...

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

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706 views

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generics - Implementing Set.addSequence in Swift

I've implemented a Set in Swift that uses Dictionary keys. I want to implement an addAll(sequence) ... purpose of SequenceType altogether. See Question&Answers more detail:os...

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

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565 views

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generics - Java: Wildcard Types Mismatch Results in Compilation Error

I've created a factory class in my project which would allow me (in theory) to create managers for any ... types that should be compatible See Question&Answers more detail:os...

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

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686 views

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generics - Resolving trait implementation conflicts

I'm trying to write some generic math functions in Rust and I keep running into the following error message: error: ... as the one from above. See Question&Answers more detail:os...

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

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843 views

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generics - Why is instanceof operator allowed on an unbounded wild card type but not on other parameterized types in Java?

I think due to type erasure , using instanceof and class literals are not allowed for parameterized generic types ... wild card types ? See Question&Answers more detail:os...

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

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584 views

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generics - Combine two types into an interface elegantly in Typescript

My goal I have a string enum E and an interface I with identical sets of keys. I want to construct a new mapped ... all values of 'dbName' } } See Question&Answers more detail:os...

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

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510 views

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generics - Why is this assignment involving wildcards legal in Java?

Most questions about wildcards want to know why something sensible is rejected by the compiler. My question is the ... it still seems "wrong". See Question&Answers more detail:os...

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

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944 views

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generics - Scala: "No manifest available for type T"

I am working on a Lift project with mixed Scala and Java code. On the Java side, I have the following relevant ... how can 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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1.0k views

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generics - How do I constrain a Kotlin extension function parameter to be the same as the extended type?

I want to write an extension method on a generic type T, where the matched type constrains a method parameter. I want this ... T.thing(p: T) {} See Question&Answers more detail:os...

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

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838 views

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generics - How can I get the sub-item type of a TObjectList<T> purely by RTTI information (i.e. without using any actual object instance) in Delphi?

I'm implementing generic code for streaming arbitrary Delphi objects using RTTI, and in order to get ... regardless of object instantiation. See Question&Answers more detail:os...

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

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606 views

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generics - Returning same collection type, differently parameterised

Daniel Sobral showed how we can create a method that returns the same collection type upon which it was called in ... ) returns a Vector[String] See Question&Answers more detail:os...

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

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622 views

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generics - Java 8 Comparator comparing static function

For the comparing source code in Comparator class public static <T, U extends Comparable<? super U>> Comparator<T ... keyExtractor.apply(c2)); } See Question&Answers more detail:os...

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

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619 views

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generics - Why does Java's Collection<E>.toArray() return an Object[] rather than an E[]?

Before Java generics, Collection.toArray() had no way to know which type of array the developer expected ... .toArray() gives ClassCastException See Question&Answers more detail:os...

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

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636 views

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generics - What would be different in Java if Enum declaration didn't have the recursive part

Please see Java Enum definition and Why in java enum is declared as Enum<E extends Enum<E>> for general discussion ... just can't believe that. See Question&Answers more detail:os...

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

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657 views

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generics - Comparable and Comparator Interface in Java

I want to write a generic Pair class, which has two members: key and value. The only requirement to this class ... same type as first.getKey() See Question&Answers more detail:os...

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

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