traits

Program to implement the is_same_type type trait in c++

由 前提是你 提交于 2019-12-01 00:55:46
HI Could anyone give a sample program to implement the is_same_type type trait in c++? #include <iostream> template< typename T1, typename T2 > struct is_same_type { enum { result = false }; }; template< typename T> struct is_same_type<T,T> { enum { result = true }; }; int main() { std::cout << is_same_type<int,float>::result << '\n' << is_same_type<char,char>::result << '\n'; return 0; } 来源： https://stackoverflow.com/questions/2639557/program-to-implement-the-is-same-type-type-trait-in-c

Calling trait static method from another static method (rust)

由 若如初见. 提交于 2019-11-30 23:07:53
Can you call a trait static method implemented by types from another trait static method implemented in the trait? For example: trait SqlTable { fn table_name() -> String; fn load(id: i32) -> Something { ... Self::table_name() // <-- this is not right ... } } This is now working thanks to Chris and Arjan (see comments/answers below) fn main() { let kiwibank = SqlTable::get_description(15,None::<Account>); } trait SqlTable { fn table_name(_: Option<Self>) -> String; fn get_description(id: i32, _: Option<Self>) -> String { println!("Fetching from {} table", SqlTable::table_name(None::<Self>) );

Scala trait - Is there an equivalent of Java interface public static field?

由 被刻印的时光 ゝ 提交于 2019-11-30 22:36:25
问题 In Java: public interface Foo { public static final int Bar = 0; } And in Scala, how can I create a trait Foo that has Bar , and I can access it as: Foo.Bar ? 回答1: You can create a companion object (to make it the equivalent of static) and define the variable there using the final val keywords (to make it the equivalent of a final constant): trait Foo { } object Foo { final val Bar = 0 } Lots more on this here 来源： https://stackoverflow.com/questions/8867316/scala-trait-is-there-an-equivalent

In scala multiple inheritance, how to resolve conflicting methods with same signature but different return type?

由 旧时模样 提交于 2019-11-30 22:07:06
问题 Consider the code below: trait A { def work = { "x" } } trait B { def work = { 1 } } class C extends A with B { override def work = super[A].work } Class C won't compile in scala 2.10, because of "overriding method work in trait A of type => String; method work has incompatible type". How to choose one specific method? 回答1: I'm afraid there is no way to do that. The super[A].work way works only if A and B have the same return types. Consider this: class D extends B .... val test: List[B] =

Program to implement the is_same_type type trait in c++

由 耗尽温柔 提交于 2019-11-30 19:25:42
问题 HI Could anyone give a sample program to implement the is_same_type type trait in c++? 回答1: #include <iostream> template< typename T1, typename T2 > struct is_same_type { enum { result = false }; }; template< typename T> struct is_same_type<T,T> { enum { result = true }; }; int main() { std::cout << is_same_type<int,float>::result << '\n' << is_same_type<char,char>::result << '\n'; return 0; } 来源： https://stackoverflow.com/questions/2639557/program-to-implement-the-is-same-type-type-trait-in

Calling trait static method from another static method (rust)

由 谁说胖子不能爱 提交于 2019-11-30 18:38:06
问题 Can you call a trait static method implemented by types from another trait static method implemented in the trait? For example: trait SqlTable { fn table_name() -> String; fn load(id: i32) -> Something { ... Self::table_name() // <-- this is not right ... } } This is now working thanks to Chris and Arjan (see comments/answers below) fn main() { let kiwibank = SqlTable::get_description(15,None::<Account>); } trait SqlTable { fn table_name(_: Option<Self>) -> String; fn get_description(id: i32,

How do I pass a closure through raw pointers as an argument to a C function?

由 女生的网名这么多〃 提交于 2019-11-30 17:04:14
问题 I'm working with WinAPI in Rust and there are some functions (like EnumWindows()) which require a callback. The callback usually accepts an additional argument (of type LPARAM which is an alias for i64 ), which you can use to pass some custom data to the callback. I have sent Vec<T> objects as LPARAM to the WinAPI callbacks and it worked fine. For instance "unpacking" an lparam value to a Vec<RECT> looked like this in my case: unsafe extern "system" fn enumerate_callback(hwnd: HWND, lparam:

UML representation of PHP trait

由 拥有回忆 提交于 2019-11-30 15:31:13
问题 I'm creating projects with Symfony2/Doctrine and try to implement traits. So far no problem on small tryouts, but I usually do UML class and sequence diagrams before deep in complex projects. What is the UML design object(s) to be used to symbolize PHP traits, which can be seen as far as I know as behaviors? Is ther any clean way to do so? Thanks a lot for your answers ! Nicolas 回答1: PHP Trait is basically UML Abstract Class or UML Class Template connected to the used-in class with the UML

UML representation of PHP trait

由 回眸只為那壹抹淺笑 提交于 2019-11-30 15:26:03
I'm creating projects with Symfony2/Doctrine and try to implement traits. So far no problem on small tryouts, but I usually do UML class and sequence diagrams before deep in complex projects. What is the UML design object(s) to be used to symbolize PHP traits, which can be seen as far as I know as behaviors? Is ther any clean way to do so? Thanks a lot for your answers ! Nicolas xmojmr PHP Trait is basically UML Abstract Class or UML Class Template connected to the used-in class with the UML Generalization Relationship utilizing the multiple inheritance notation See also: Figure "UML Diagram

Is there something wrong with an abstract value used in trait in scala?

由 爷，独闯天下 提交于 2019-11-30 10:54:42
I have trait Invoker { val method: Method } Intellij IDEA code inspection is warning me that "Abstract value used in trait". Everything compiles fine. Is there something wrong with having an abstract value in a trait? If so, how should I specify that all extenders of the trait must define a method property? What is meant by this is the following weirdness: trait A { val i: String def j: String } class C extends A { println ("val i = " + i) println ("def j = " + j) val i = "i" def j = "j" } val c = new C // prints // val i = null // def j = j So, as you can see i is initialised to it default
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