enumeration

How to get correct value type when extending Scala Enumeration.Val

由 試著忘記壹切 提交于 2019-12-07 09:57:03
问题 While there are many questions on S/O regarding difficulties with Scala Enumeration, I haven't found a question that addresses my problem. Specifically, I am trying to translate the Planet example from the Oracle Java enum docs into the Scala Enumeration idiom so as to better understand the workings and pro's & con's of the Scala form. My ported code so far appears below and, suffice to say, it does not compile as might be expected from the principle of least surprise. Apart from type casting

Should I store my Enums at database level or in the application logic (.NET)?

由 ≯℡__Kan透↙ 提交于 2019-12-07 07:28:57
问题 I have a table, lets call it Objects. It has a predefined set of records looking like this: ObjectId ObjectName 1 Salmon 2 Trout 3 Seabass 4 Shark Etc.. So, this I would like to implement somehow as an enum. But what's the best way, implement it in the database creating tables for it or in the application logic in an CommonEnums codebehind file etc? 回答1: We add them in both places, we use code generator to keep in sync the values. The main values are in the Enum but the template automatically

Differences between scala and java enumerations

由 我的未来我决定 提交于 2019-12-07 05:44:01
问题 I read an answer on SO where someone said that scala enumerations are useless, and you should just use java enumerations instead if you really need too. Although I have used java enumerations before, I can't say I fully understand them as I don't code in java during my day job. Can someone explain the differences between scala and java enumerations, and where exactly the shortcomings in scala enums are? 回答1: The main advantage of Scala's Enumeration is the regularity of the syntax. If you

Does Scheme/Racket have an enumeration operation?

由 天大地大妈咪最大 提交于 2019-12-07 05:38:53
问题 Does Scheme/Racket have an enumeration notation equivalent to the [a..b] notation in Haskell? In Haskell, [1..5] evaluates to a list [1,2,3,4,5]. 回答1: (for/list ([i (in-range 1 6)]) i) (sequence->list (in-range 1 6)) (require srfi/1) (iota 5 1) 回答2: (for/list ([i 5]) (+ 1 i)) (build-list 5 add1) Also, (in-range 1 6) (which is a sequence) by itself is useful in many contexts. 来源： https://stackoverflow.com/questions/7144248/does-scheme-racket-have-an-enumeration-operation

Fast Enumeration With an NSMutableArray that holds an NSDictionary

由 99封情书 提交于 2019-12-07 05:23:52
问题 Is it possible to use fast enumeration with an NSArray that contains an NSDictionary? I'm running through some Objective C tutorials, and the following code kicks the console into GDB mode NSMutableArray *myObjects = [NSMutableArray array]; NSArray *theObjects = [NSArray arrayWithObjects:@"easy as 1",@"easy as two", @"Easy as Three"]; NSArray *theKeys = [NSArray arrayWithObjects:@"A",@"B",@"C"]; NSDictionary *theDict = [NSDictionary dictionaryWithObjects:theObjects forKeys:theKeys];

What is the most efficient way to enumerate vertices of k dimensional hypercube in C++?

由 给你一囗甜甜゛ 提交于 2019-12-07 04:44:53
问题 Basic Question: I have a k dimensional box. I have a vector of upper bounds and lower bounds. What is the most efficient way to enumerate the coordinates of the vertices? Background: As an example, say I have a 3 dimensional box. What is the most efficient algorithm / code to obtain: vertex[0] = ( 0, 0, 0 ) -> ( L_0, L_1, L_2 ) vertex[1] = ( 0, 0, 1 ) -> ( L_0, L_1, U_2 ) vertex[2] = ( 0, 1, 0 ) -> ( L_0, U_1, L_2 ) vertex[3] = ( 0, 1, 1 ) -> ( L_0, U_1, U_2 ) vertex[4] = ( 1, 0, 0 ) -> ( U_0

How to index all the derived components in a base component list in Entity

由 99封情书 提交于 2019-12-06 11:43:16
I am trying to do a entity component system design for simulation. Here is what confuses me now. I am trying to make a Entity class Entity.h class Entity { public: Entity(); virtual ~Entity() = 0; //---------------------Methods---------------------// void AddComponent(const shared_ptr<Component> component); template<class T> T* GetComponent() const; //---------------------Members---------------------// vector<shared_ptr<Component>> m_components; } Entity.cpp template<typename T> T* Entity::GetComponent() const { Component::component_type_t typeIndex = /*T::component_type*/ T* returnPtr =

Why do iterators behave differently on exception than LINQ enumerables?

由 ぃ、小莉子 提交于 2019-12-06 09:52:49
I am studying the internal mechanics of the iterator methods, and I noticed a strange difference in behavior between the IEnumerator<T> obtained by an iterator and the IEnumerator<T> obtained by a LINQ method. If an exception happens during the enumeration, then: The LINQ enumerator remains active. It skips an item but continues producing more. The iterator enumerator becomes finished. It does not produce any more items. Example. An IEnumerator<int> is enumerated stubbornly until it completes: private static void StubbornEnumeration(IEnumerator<int> enumerator) { using (enumerator) { while

Z3 Enumerating all satisfying assignments

由 元气小坏坏 提交于 2019-12-06 08:00:48
I am trying to solve a problem similar to the one here ( Z3: finding all satisfying models ) where I need to find all satisfying assignments of SMT formulae that contain set variables. I understand the idea in the link since it is similar to what some SAT solvers do to iterate through solutions: add the negation of the solution to obtain a different solution. However, when I use the set variables (which are implemented as arrays in Z3) the things get a little complicated or perhaps I miss something. Assume that I have two constraints added to the solver as follows: EnumSort rSort = ctx

ActiveRecord and using reject method

由 只愿长相守 提交于 2019-12-06 07:37:05
I have a model that fetches all the games from a particular city. When I get those games I want to filter them and I would like to use the reject method, but I'm running into an error I'm trying to understand. # STEP 1 - Model class Matches < ActiveRecord::Base def self.total_losses(cities) reject{ |a| cities.include?(a.winner) }.count end end # STEP 2 - Controller @games = Matches.find_matches_by("Toronto") # GOOD! - Returns ActiveRecord::Relation # STEP 3 - View cities = ["Toronto", "NYC"] @games.total_losses(cities) # FAIL - undefined method reject for #<Class:0x00000101ee6360> # STEP 3 -
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