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• Scala/Erlang use something like greenThread or not ?

  - by CHAPa

  Hi all, Im reading a lot about how scala/Erlang does lightweight threads and your concurrency model ( Actor Model ). Off course, some doubts appear in my head. Scala/Erlang use a approach similar to the old thread model used by java (greenThread) ? for example, suppose that there is a machine with 2 cores, so the scala/erlang environment will fork one thread per processor ? The other threads will be scheduled by user-space( scala VM / erlang vm ) environment. is it correct ? how under the hood that really work ? thanks a lot.

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• Best practice to use MS Excel as a database

  - by Ying

  In office, it is popular to use MS Excel to store data. In most cases, the data is structured, which means it is suitable for a database. I know peole prefer MS Excel for it is easy to change the data structure and data value. So I have an idea to use MS Excel as a database IF people follow a general rule to store data. In other words, by a best practice to use MS Excel as a database. I have thought to use MS Access to store data, but it is expensive and not popular as MS Excel. I don't mind to buy such a solution, especially when it is for .Net platform. Any ideas or suggestions are welcome.

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• Empty list in appengine datastore: java vs python

  - by lOranger

  I have the following java model class in AppEngine: public class Xyz ... { @Persistent private Set<Long> uvw; } When saving an object Xyz with an empty set uvw in Java, I get a "null" field (as listed in the appengine datastore viewer). When I try to load the same object in python (through remote_api), as defined by the following python model class: class Xys(db.Model): uvw = db.ListProperty(int) I get a "BadValueError: Property uvw is required". When saving another object of the same class in python with an empty uvw list, the datastore viewer print a "missing" field. Apparently empty lists storage handling differs between Java and python and lead to "incompatible" objects. Thus my question: Is there a way to, either: force Java to store an empty list as a "missing" field, force Python to gracefully accept a "null" list as an empty list when loading the object? Or any other suggestion on how to handle empty list field in both languages. Thanks for your answers!

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• Converting app to MVC and running it in both console and gui

  - by terence6

  I have a simple java gui calculator, with 3 number systems (there are some bugs but that doesn't matter now). Currently all code is in one file. My task is to rewrite it as MVC, and add possibility to run it in either gui or console mode. How should I divide this program to organise it as M-V-C ? Is it written properly enough to add console functionality to it? (guess I'll have to change all methods invoking to JLabel Output to something simply storing an output String as a model argument and then having View to get it). Here's the starting code : http://paste.pocoo.org/show/224566/ Here's what I already have : Main : http://paste.pocoo.org/show/224567/ Model : http://paste.pocoo.org/show/224570/ View : http://paste.pocoo.org/show/224569/ Controller : http://paste.pocoo.org/show/224568/ I don't have view in my model so I can't call to Output. That's the first problem I can see.

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• Edit form not being instantiated

  - by 47

  I have two models like this: class OptionsAndFeatures(models.Model): options = models.TextField(blank=True, null=True) entertainment = models.TextField(blank=True, null=True) seats_trim = models.TextField(blank=True, null=True) convenience = models.TextField(blank=True, null=True) body_exterior = models.TextField(blank=True, null=True) lighting = models.TextField(blank=True, null=True) safety = models.TextField(blank=True, null=True) powertrain = models.TextField(blank=True, null=True) suspension_handling = models.TextField(blank=True, null=True) specs_dimensions = models.TextField(blank=True, null=True) offroad_capability = models.TextField(blank=True, null=True) class Vehicle(models.Model): ... options_and_features = models.ForeignKey(OptionsAndFeatures, blank=True, null=True) I have a model form for the OptionsAndFeaturesclass that I'm using in both the add and edit views. In the add view it works just fine. But the edit view renders the OptionsAndFeatures as blank. The code for the edit view is as follows: def edit_vehicle(request, stock_number=None): vehicle = get_object_or_404(Vehicle, stock_number=stock_number) if request.method == 'POST': # save info else: vehicle_form = VehicleForm(instance=vehicle) photos = PhotosFormSet(instance=vehicle) options = OptionsForm(instance=vehicle) #render_to_reponse What could be the problem here?

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• Singleton pattern and broken double checked locking in real world java application

  - by saugata

  I was reading the article Double-checked locking and the Singleton pattern, on how double checked locking is broken, and some related questions here on stackoverflow. I have used this pattern/idiom several times without any issues. Since I have been using Java 5, my first thought was that this has been rectified in Java 5 memory model. However the article says This article refers to the Java Memory Model before it was revised for Java 5.0; statements about memory ordering may no longer be correct. However, the double-checked locking idiom is still broken under the new memory model. I'm wondering if anyone has actually run into this problem in any application and under what conditions.

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• problem in leigeber's sorting

  - by developer

  iam using leigeber's sorting javascript to sort my data on my page......i took the js from here :- leigeber's sorting javascript Now this is shwoing highlighted sorted column and all and its all perfect.Now iam having some negative and some positive values in my data and i want to show those negative data in red color and positive in green.This whole sorting thing is using js and css to do the highlighting and sorting.Iam a bit confused now and cant make it out that how i can assign red color to the negative ones and green to the positive ones as js is returning the data as an object i.e. a complete row and i cant make 1 column's data red or green.Will it be done by js itself or with the help of stylesheet to find -ves and +ves.Im totally lost and dont know how to do it.Please help!!!! this is an example of hte data iam using this whole sorting thing on:- -Name- -Price- -loss- -Pts- abc 361.15 -5.68 -21.75 abc2 1072.35 -5.24 -59.25 abc3 512.35 5.24 28.35 abc4 335.2 -5.02 -17.7 abc5 318.6 5.01 -16.8 abc6 76.15 -4.15 3.3

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• Re-using unit tests for models using STI

  - by TenJack

  I have a number of models that use STI and I would like to use the same unit test to test each model. For example, I have: class RegularList < List class OtherList < List class ListTest < ActiveSupport::TestCase fixtures :lists def test_word_count list = lists(:regular_list) assert_equal(0, list.count) end end How would I go about using the test_word_count test for the OtherList model. The test is much longer so I would rather not have to retype it for each model. Thanks.

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• Dynamic Linq Library Help

  - by Alon

  Hi, I have the following class: public class Item { public Dictionary<string, string> Data { get; set; } } and a list of it: List<Item> items; I need to filter and order this list dynamicly using SQL-Like strings. The catch is, that I need to order it by the Data dictionary. For example: Order By Data["lastname"] or Where Data["Name"].StartsWith("a"). I thought to use the dynamic linq library, but is there any way that my clients can write without the Data[]? For example: Name.StartsWith("abc") instead of Data["Name"].StartsWith("abc") ? Thank you.

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• Python utf-8 decoding issue with hashlib.digest() method

  - by Sorw

  Hello StackOverflow community, Using Google App Engine, I wrote a keyToSha256() method within a model class (extending db.Model) : class Car(db.Model): def keyToSha256(self): keyhash = hashlib.sha256(str(self.key())).digest() return keyhash When displaying the output (ultimately within a Django template), I get garbled text, for example : ?????_??!`?I?!?;?QeqN??Al?'2 I was expecting something more in line with this : 9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08 Am I missing something important ? Despite reading several guides on ASCII, Unicode, utf-8 and the like, I think I'm still far from mastering the secrets of string encoding/decoding. After browsing StackOverflow and searching for insights via Google, I figured out I should ask the question here. Any idea ? Thanks !

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• Java to Qt code convert

  - by user289175

  Hello, I'm teaching my self Qt; in the same time I don't want to lose my Java skills in Qt. I stacked in some codes to do it in Qt, I tried many times as well as search in the net. Code # 1 Object[] names = jList1.getSelectedValues(); String msg = ""; for (Object o : names) msg += o; Code # 2 DefaultListModel model; model = new DefaultListModel(); jList1.setModel(model); Code # 3 if(!jList1.isSelectionEmpty()) I didn't find Empty method :-( I'm going to do some Qt's video tutorials on youtube, but before that I need to solve the above codes. If any programmer can help I will be thankful; Thanks in advance At the end I would like to thanks the experts who are spent thier value times to help others

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• Ruby on Rails Join Table Associations

  - by Eef

  Hey, I have a Ruby on Rails application setup like so: User Model has_and_belongs_to_many :roles Role Model has_many :transactions has_and_belongs_to_many :users Transaction Model belongs_to :role This means that a join table is used called roles_users and it also means that a user can only see the transactions that have been assigned to them through roles, usage example: user = User.find(1) transactions = user.roles.first.transactions This will return the transactions which are associated with the first role assigned to the user. If a user has 2 roles assigned to them, at the moment to get the transactions associated with the second role I would do: transactions = user.roles.last.transactions I am basically trying to figure out a way to setup an association so I can grab the user's transactions via something like this based on the roles defined in the association between the user and roles: user = User.find(1) transactions = user.transactions I am not sure if this is possible? I hope you understand what I am trying to do.

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• django admin gives warning "Field 'X' doesn't have a default value"

  - by noam

  I have created two models out of an existing legacy DB , one for articles and one for tags that one can associate with articles: class Article(models.Model): article_id = models.AutoField(primary_key=True) text = models.CharField(max_length=400) class Meta: db_table = u'articles' class Tag(models.Model): tag_id = models.AutoField(primary_key=True) tag = models.CharField(max_length=20) article=models.ForeignKey(Article) class Meta: db_table = u'article_tags' I want to enable adding tags for an article from the admin interface, so my admin.py file looks like this: from models import Article,Tag from django.contrib import admin class TagInline(admin.StackedInline): model = Tag class ArticleAdmin(admin.ModelAdmin): inlines = [TagInline] admin.site.register(Article,ArticleAdmin) The interface looks fine, but when I try to save, I get: Warning at /admin/webserver/article/382/ Field 'tag_id' doesn't have a default value

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• How can I disable multiple links with jQuery?

  - by Samantha J

  I have the following HTML: <a title="Login" data-href="/MyAccount/Access/Login" data-title="Admin" data-entity="n/a" id="loginLink" class="nav-button dialogLink"><b>Login</b></a> <a title="Register" data-href="/MyAccount/Access/Register" data-title="Admin" data-entity="n/a" id="registerLink" class="nav-button dialogLink"><b>Register</b></a> When a user clicks on the #loginLink or #registerLink I would like to disable the link and call a dialog script. I created the following function: $("#loginLink, #registerLink") .click(function () { $('#loginLink').prop('disabled', true); $('#registerLink').prop('disabled', true); dialog(this); }); It calls the dialog correctly but doesn't disable the links and if I click the buttons more than once it calls up more than one dialog box. Is there something I am doing wrong? I can't see why it would not work.

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• Django syncdb not making tables for my app

  - by Rosarch

  It used to work, and now it doesn't. python manage.py syncdb no longer makes tables for my app. From settings.py: INSTALLED_APPS = ( 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.sites', 'mysite.myapp', 'django.contrib.admin', ) What could I be doing wrong? The break appeared to coincide with editing this model in models.py, but that could be total coincidence. I commented out the lines I changed, and it still doesn't work. class MyUser(models.Model): user = models.ForeignKey(User, unique=True) takingReqSets = models.ManyToManyField(RequirementSet, blank=True) takingTerms = models.ManyToManyField(Term, blank=True) takingCourses = models.ManyToManyField(Course, through=TakingCourse, blank=True) school = models.ForeignKey(School) # minCreditsPerTerm = models.IntegerField(blank=True) # maxCreditsPerTerm = models.IntegerField(blank=True) # optimalCreditsPerTerm = models.IntegerField(blank=True) UPDATE: When I run python manage.py loadddata initial_data, it gives an error: DeserializationError: Invalid model identifier: myapp.SomeModel Loading this data had worked fine before. This error is thrown on the very first data object in the data file.

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• How does Fluent NHibernate support the Import Entity

  - by Bender

  I want to create a strongly type object from a fluent NHibernate query. If I were using HQL and NHibernate I belive I would need: the class for the output Namespace Model Public Class namecount Public Overridable Property lastname() as string ... Public Overridable Property lastnamecount() as integer ... Public Sub New(lastname as string, count as integer) ... End Class End Namespace an .hbm.xml file <?xml ...> <hibernate-mapping ...> <import class="model.namecount,model"> </hibernate-mapping> and of course the query _session.createquery("select new namecount(lastname, count(lastname)) ...") (The above is a paraphrased example taken from one of the 2008 SummerofNHibernate videos) I cannot find any examples of how to do this with fluent (even in C#), is it possible? If it isn't is there a VB example of how to mix Fluent and .hbm.xml

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• Copy Structure To Another Program

  - by Steven

  Long story, long: I am adding a web interface (ASPX.NET: VB) to a data acquisition system developed with LabVIEW which outputs raw data files. These raw data files are the binary representation of a LabVIEW cluster (essentially a structure). LabVIEW provides functions to instantiate a class or structure or call a method defined in a .NET DLL file. I plan to create a DLL file containing a structure definition and a class with methods to transfer the structure. When the webpage requests data, it would call a LabVIEW executable with a filename parameter. The LabVIEW code would instantiate the structure, populate the structure from the data file, then call the method to transfer the data back to the website. Long story, short: How do you recommend I transfer (copy) an instance of a structure from one .NET program to a VB.NET program? Ideas considered: sockets, temp file, xml file, config file, web services, CSV, some type of serialization, shared memory

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• Is it bad practice to use the namespace to identify the verb or should it always be in the class nam

  - by Nick Allen - Tungle139

  For example is MyLibrary.Data.Import.Hotels Bad Vs MyLibrary.Data.Import.ImportHotels Or even MyLibrary.Data.ImportHotels

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• Java NIO SocketChannel writing problem

  - by Nilesh

  I am using Java NIO's SocketChannel to write : int n = socketChannel.write(byteBuffer); Most of the times the data is sent in one or two parts; i.e. if the data could not be sent in one attemmpt, remaining data is retried. The issue here is, sometimes, the data is not being sent completely in one attempt, rest of the data when tried to send multiple times, it occurs that even after trying several times, not a single character is being written to channel, finally after some time the remaning data is sent. What could be the cause of such behaviour? Could external factors such as RAM, etc cause the hindarance? Please help me solve this issue. If any other information is required please let me know. Thanks

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• DataBinding a DropDownList in ASP.NET MVC 2

  - by Daniel Coffman

  I'm extremely frustrated trying to switch to MVC after a couple years of webforms development. Here's my extremely simple problem that I can't manage to solve: I have a list of States in a table called StateProvince. I have a DropDownList. I want the DropDownList to display all of the States in the StateProvince table and post the selected state back on HTTP PUT. This is what I'm doing: <%: Html.DropDownListFor(model = model.StateProvinceId, new SelectList(Model.StateProvinces, "StateProvinceId", "Name") )% I'm getting an Object reference not set to an instance of an object. Why? How can I make this work? Keep it simple, I know nothing about MVC.

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• Why is Django reverse() failing with unicode?

  - by JeffS

  Here is a django models file that is not working as I would expect. I would expect the to_url method to do the reverse lookup in the urls.py file, and get a url that would correspond to calling that view with arguments supplied by the Arguments model. from django.db import models class Element(models.Model): viewname = models.CharField(max_length = 200) arguments = models.ManyToManyField('Argument', null = True, blank = True ) @models.permalink def to_url(self): d = dict( self.arguments.values_list('key', 'value') ) return (self.viewname, (), d) class Argument(models.Model): key = models.CharField(max_length=200) value = models.CharField(max_length=200) The value d ends up as a dictionary from a unicode string to another unicode string, which I believe, should work fine with the reverse() method that would be called by the permalink decorator, however, it results in: TypeError: reverse() keywords must be strings

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• Show different sub-sets in edit view

  - by Martin R-L

  In the context of C# 4, ASP.NET MVC 2, and NHibernate; I've got the following scenario: Let's assume an entity Product that have an association to ProductType. In a product edit view; how do I implement that only a sub-set of the product's properties are shown in an elegant and DRY way? Use a product view model builder, and from different view models automagically generate the view with my own Html.EditorForModel() (including drop-downs and other stuff not out-of-the-box)? Attribute the properties of one view model and use the Html.EditorForModel() way aforementioned? Use one model, but implement different web controls (view strategies) (can it be done DRY?)? Something else entirely?

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• GDB says that a KVO observer is registered even though it is not (or is it?).

  - by Paperflyer

  When my application is closed, the main controller class removes itself as Observer from the model and then releases the model. Like this: - (void)dealloc { [theModel removeObserver:self forKeyPath:@"myValue"]; [theModel release]; [super dealloc]; } And right after that, the debugger says: 2010-04-29 14:07:40.294 MyProgram[13678:a0f] An instance 0x116f2e880 of class TheModel was deallocated while key value observers were still registered with it. Observation info was leaked, and may even become mistakenly attached to some other object. Set a breakpoint on NSKVODeallocateBreak to stop here in the debugger. Here's the current observation info: <NSKeyValueObservationInfo 0x100288450> ( <NSKeyValueObservance 0x1002aca90: Observer: 0x116f40ec0, Key path: myValue, Options: <New: YES, Old: NO, Prior: NO> Context: 0x0, Property: 0x116f80430> ) where 0x116f2e880 is indeed the model and 0x116f40ec0 is indeed the controller. How can the controller still be an observer when it just removed itself as an observer?

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• python: sorting

  - by nabizan

  hi im doing a loop so i could get dict of data, but since its a dict it's sorting alphabetical and not as i push it trought the loop ... is it possible to somehow turn off alphabetical sorting? here is how do i do that data = {} for item in container: data[item] = {} ... for key, val in item_container.iteritems(): ... data[item][key] = val whitch give me something like this data = { A : { K1 : V1, K2 : V2, K3 : V3 }, B : { K1 : V1, K2 : V2, K3 : V3 }, C : { K1 : V1, K2 : V2, K3 : V3 } } and i want it to be as i was going throught the loop, e.g. data = { B : {K2 : V2, K3 : V3, K1 : V1}, A : {K1 : V1, K2 : V2, K3 : V3}, C : {K3 : V3, K1 : V1, K2 : V2} }

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• unexpected T_TRY, expecting T_FUNCTION error message, not sure why ?

  - by Rachel

  I am getting unexpected T_TRY, expecting T_FUNCTION error message and am not sure as too why am getting that, can't we use try and catch block inside class like this: class Processor { protected $dao; protected $fin; try { public function __construct($file) { //Open File for parsing. $this->fin = fopen($file,'w+') or die('Cannot open file'); // Initialize the Repository DAO. $this->dao = new Dao('some name'); } public function initiateInserts() { while (($data=fgetcsv($this->fin,5000,";"))!==FALSE) { $initiate_inserts = $this->dao->initiateInserts($data); } } public function initiateCUpdates() { while (($data=fgetcsv($this->fin,5000,";"))!==FALSE) { $initiate_updates = $this->dao->initiateCUpdates($data); } } public function initiateExecuteIUpdates() { while (($data=fgetcsv($this->fin,5000,";"))!==FALSE) { $initiate_updates = $this->dao->initiateIUpdates($data); } } } catch (Exception $e) { } }

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