# Search Results

• ### Is there a way to force ContourPlot re-check all the points on the each stage of it's recursion algorithm?

##### - by Alexey Popkov
Hello, Thanks to this excellent analysis of the Plot algorithm by Yaroslav Bulatov, I now understand the reason why Plot3D and ContourPlot fail to draw smoothly functions with breaks and discontinuities. For example, in the following case ContourPlot fails to draw contour x^2 + y^2 = 1 at all: ContourPlot[Abs[x^2 + y^2 - 1], {x, -1, 1}, {y, -1, 1}, Contours -> {0}] It is because the algorithm does not go deeply into the region near x^2 + y^2 = 1. It "drops" this region on an initial stage and do not tries to investigate it further. Increasing MaxRecursion does nothing in this sense. And even undocumented option Method -> {Refinement -> {ControlValue -> .01 \[Degree]}} does not help (but makes Plot3D a little bit smoother). The above function is just a simple example. In real life I'm working with very complicated implicit functions that cannot be solved analytically. Is there a way to get ContourPlot to go deeply into such regions near breaks and discontinuities?

• ### Writing functions of tuples conveniently in Scala

##### - by Alexey Romanov
Quite a few functions on Map take a function on a key-value tuple as the argument. E.g. def foreach(f: ((A, B)) ? Unit): Unit. So I looked for a short way to write an argument to foreach: > val map = Map(1 -> 2, 3 -> 4) map: scala.collection.immutable.Map[Int,Int] = Map(1 -> 2, 3 -> 4) > map.foreach((k, v) => println(k)) error: wrong number of parameters; expected = 1 map.foreach((k, v) => println(k)) ^ > map.foreach({(k, v) => println(k)}) error: wrong number of parameters; expected = 1 map.foreach({(k, v) => println(k)}) ^ > map.foreach(case (k, v) => println(k)) error: illegal start of simple expression map.foreach(case (k, v) => println(k)) ^ I can do > map.foreach(_ match {case (k, v) => println(k)}) 1 3 Any better alternatives?

• ### Scala: getting the name of the class the trait is mixed in

##### - by Alexey Romanov
Given an instance of a class, we can obviously return its name: trait MixedInClassDiscovery { val className = this.getClass.getName } class AClass extends MixedInClassDiscovery { ... this.className // returns "AClass" ... } But this way uses reflection, once for every instance of AClass. Can the same be done once for every class, instead? One solution which comes to mind is to mix it into companion objects instead of classes themselves.

• ### Scala: when are singleton objects constructed?

##### - by Alexey Romanov
In object O { // construction code and member initialization } construct, when is this code going to be run?

• ### Class name to view path

##### - by Alexey Poimtsev
Hi, I have a RoR application and model SomeModel. I have views for this model and I want to know - is there any method to get the view's path? Of course I can use for this model instance m = SomeModel.new v = m.class.class_name.pluralize.downcase It's working, but maybe you know a better way? :)

• ### Custom SWT controls and layouts

##### - by Alexey Romanov
What custom controls and layouts for SWT/JFace do you use? Preferably, list one per answer.

• ### Feature-level behavior testing tools for Java/Scala

##### - by Alexey Romanov
Is there a Java or Scala equivalent to Cucumber/SpecFlow? One possibility is using Cucumber with JRuby; any others?

• ### Should I check-in IDE project files to version control system?

##### - by Alexey Kalmykov
For a Java project (with the team of 5-10 developers) should I store my IDE project files (e.g. Eclipse or IntelliJ Idea) in version control system (currently I store only build scripts)? What's the best practice? PS Do you aware of any tools to automatically generate project files for common Java IDEs according to some descriptor?

• ### Erlang: simple refactoring

##### - by alexey
Consider the code: f(command1, UserId) -> case is_registered(UserId) of true -> %% do command1 ok; false -> not_registered end; f(command2, UserId) -> case is_registered(UserId) of true -> %% do command2 ok; false -> not_registered end. is_registered(UserId) -> %% some checks Now imagine that there are a lot of commands and they are all call is_registered at first. Is there any way to generalize this behavior (refactor this code)? I mean that it's not a good idea to place the same case in all the commands.

• ### Google Chrome && (cache || memory leaks).

##### - by Alexey Ogarkov
Hello All, I have a big problem with Google Chrome and its memory. My app is displaying to user several image charts and reloads them every 10s. In the interval i have code like that var image = new Image(); var src = 'myurl/image'+new Date().getTime(); image.onload = function() { document.getElementById('myimage').src = src; image.onload = image.onabort = image.onerror = null; } image.src = src; So i have no memory leaks in Firefox and IE. Here the response headers for images Server Apache-Coyote/1.1 Vary * Cache-Control no-store (// I try no-cache, must-revalidate and so on here) Content-Type image/png Content-Length 11131 Date Mon, 31 May 2010 14:00:28 GMT Vary * taken from here In about:cache page there is no my cached images. If i enable purge-memory-button for chrome (--purge-memory-button parameter) it`s not help. Images is in PNG24. So i think that the problem is not in cache. May be Google Chrome is not releasing memory for old images. Please help. Any suggestions. Thanks.

#### Read the article

##### - by alexey
Facebook docs: Facebook Platform supports two different OAuth 2.0 flows for user login: server-side (known as the authentication code flow in the specification) and client-side (known as the implicit flow). The server-side flow is used whenever you need to call the Graph API from your web server. The client-side flow is used when you need to make calls to the Graph API from a client, such as JavaScript running in a Web browser or from a native mobile or desktop app. What is the difference between access tokens taken by these flows? It seems like they length differ. Can we use server-side flow token on a client? And otherwise, can we use client-side flow token on a server?

• ### Efficient way to remove empty lists from lists without evaluating held expressions?

##### - by Alexey Popkov
In previous thread an efficient way to remove empty lists ({}) from lists was suggested: Replace[expr, x_List :> DeleteCases[x, {}], {0, Infinity}] Using the Trott-Strzebonski in-place evaluation technique this method can be generalized for working also with held expressions: f1[expr_] := Replace[expr, x_List :> With[{eval = DeleteCases[x, {}]}, eval /; True], {0, Infinity}] This solution is more efficient than the one based on ReplaceRepeated: f2[expr_] := expr //. {left___, {}, right___} :> {left, right} But it has one disadvantage: it evaluates held expressions if they are wrapped by List: In[20]:= f1[Hold[{{}, 1 + 1}]] Out[20]= Hold[{2}] So my question is: what is the most efficient way to remove all empty lists ({}) from lists without evaluating held expressions? The empty List[] object should be removed only if it is an element of another List itself. Here are some timings: In[76]:= expr = Tuples[Tuples[{{}, {}}, 3], 4]; [email protected][#[expr]] & /@ {f1, f2, f3} pl = Plot3D[Sin[x y], {x, 0, Pi}, {y, 0, Pi}]; [email protected][#[pl]] & /@ {f1, f2, f3} Out[77]= {0.581, 0.901, 5.027} Out[78]= {0.12, 0.21, 0.18} Definitions: Clear[f1, f2, f3]; f3[expr_] := FixedPoint[ Function[e, Replace[e, {a___, {}, b___} :> {a, b}, {0, Infinity}]], expr]; f1[expr_] := Replace[expr, x_List :> With[{eval = DeleteCases[x, {}]}, eval /; True], {0, Infinity}]; f2[expr_] := expr //. {left___, {}, right___} :> {left, right};

• ### What are the features of dynamic languages (like Ruby or Clojure) which you are missing in Scala?

##### - by Alexey
When you choose to program in dynamic languages you sacrifice performance, some IDE capabilities and compile-type checks in favour of flexibility. So what you practically lose when you choose stytic-typed langauge like Scala (or F#, Haskell, C#) instead of dynamic ones (which has macros or runtime metaprogramming capabilities)?

• ### How long can rails keep Ajax open

##### - by Alexey
My application is suppose to constantly update the page without any user interaction. The criteria is that the page just has to be there, as an extra window on the monitor so the user can see the information get updated real time. I'm using the Ajax in jQuery with Rails, and my question is - how long will the .erb page keep Ajax open? Will there be a point where I have to refresh the page or re-initialize? Or will that won't be a problem at all?

• ### How can I host many identical java web applications?

##### - by aelkin
Hello, I have a problem. I need to host many (tens, hundreds) of small identical JAVA web applications that have different loads during one time. I want to use Glassfish V3. Do I need to use a load balancer and clusters or something else? Advise where can I find information about similar problems and their solutions... Best regards, Alexey.

• ### How do you formulate the Domain Model in Domain Driven Design properly (Bounded Contexts, Domains)?

##### - by lko
Say you have a few applications which deal with a few different Core Domains. The examples are made up and it's hard to put a real example with meaningful data together (concisely). In Domain Driven Design (DDD) when you start looking at Bounded Contexts and Domains/Sub Domains, it says that a Bounded Context is a "phase" in a lifecycle. An example of Context here would be within an ecommerce system. Although you could model this as a single system, it would also warrant splitting into separate Contexts. Each of these areas within the application have their own Ubiquitous Language, their own Model, and a way to talk to other Bounded Contexts to obtain the information they need. The Core, Sub, and Generic Domains are the area of expertise and can be numerous in complex applications. Say there is a long process dealing with an Entity for example a Book in a core domain. Now looking at the Bounded Contexts there can be a number of phases in the books life-cycle. Say outline, creation, correction, publish, sale phases. Now imagine a second core domain, perhaps a store domain. The publisher has its own branch of stores to sell books. The store can have a number of Bounded Contexts (life-cycle phases) for example a "Stock" or "Inventory" context. In the first domain there is probably a Book database table with basically just an ID to track the different book Entities in the different life-cycles. Now suppose you have 10+ supporting domains e.g. Users, Catalogs, Inventory, .. (hard to think of relevant examples). For example a DomainModel for the Book Outline phase, the Creation phase, Correction phase, Publish phase, Sale phase. Then for the Store core domain it probably has a number of life-cycle phases. public class BookId : Entity { public long Id { get; set; } } In the creation phase (Bounded Context) the book could be a simple class. public class Book : BookId { public string Title { get; set; } public List<string> Chapters { get; set; } //... } Whereas in the publish phase (Bounded Context) it would have all the text, release date etc. public class Book : BookId { public DateTime ReleaseDate { get; set; } //... } The immediate benefit I can see in separating by "life-cycle phase" is that it's a great way to separate business logic so there aren't mammoth all-encompassing Entities nor Domain Services. A problem I have is figuring out how to concretely define the rules to the physical layout of the Domain Model. A. Does the Domain Model get "modeled" so there are as many bounded contexts (separate projects etc.) as there are life-cycle phases across the core domains in a complex application? Edit: Answer to A. Yes, according to the answer by Alexey Zimarev there should be an entire "Domain" for each bounded context. B. Is the Domain Model typically arranged by Bounded Contexts (or Domains, or both)? Edit: Answer to B. Each Bounded Context should have its own complete "Domain" (Service/Entities/VO's/Repositories) C. Does it mean there can easily be 10's of "segregated" Domain Models and multiple projects can use it (the Entities/Value Objects)? Edit: Answer to C. There is a complete "Domain" for each Bounded Context and the Domain Model (Entity/VO layer/project) isn't "used" by the other Bounded Contexts directly, only via chosen paths (i.e. via Domain Events). The part that I am trying to figure out is how the Domain Model is actually implemented once you start to figure out your Bounded Contexts and Core/Sub Domains, particularly in complex applications. The goal is to establish the definitions which can help to separate Entities between the Bounded Contexts and Domains.

• ### struts2 trim all string obtained from forms

##### - by aelkin
Hi All, I develop web application using struts2. I want to improve getting string from forms. For this need trim all string and if obtained string is empty then set null to field. For this, I created StringConverter. public class StringConverter extends StrutsTypeConverter { @Override public Object convertFromString(Map context, String[] strings, Class toClass) { if (strings == null || strings.length == 0) { return null; } String result = strings[0]; if (result == null) { return null; } result = result.trim(); if (result.isEmpty()) { return null; } return result; } @Override public String convertToString(Map context, Object object) { if (object != null && object instanceof String) { return object.toString(); } return null; } } Next, I added row to xwork-conversion.properties java.lang.String=com.mypackage.StringConverter Thats all. But I did not get the desired result. convertToString() method is called when jsp build form, but convertFromString() doesn't invoke. What I do wrong? How can I get the same behaviour using another way? Please, not offer solutions such as: remove the value of such form elements using javascript. create util method which will make it using reflection. Then call it for each form bean. Thanks in advance, Alexey.