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• Tokenizing numbers for a parser

  - by René Nyffenegger

  I am writing my first parser and have a few questions conerning the tokenizer. Basically, my tokenizer exposes a nextToken() function that is supposed to return the next token. These tokens are distinguished by a token-type. I think it would make sense to have the following token-types: SYMBOL (such as <, :=, ( and the like REMARK (or a comment) NUMBER IDENT (such as the name of a function or a variable) STRING (Something enclosed between "....") Now, do you think this makes sense? Also, I am struggling with the NUMBER token-type. Do you think it makes more sense to further split it up into a NUMBER and a FLOAT token-type? Without a FLOAT token-type, I'd receive NUMBER (eg 402), a SYMBOL (.) followed by another NUMBER (eg 203) if I were about to parse a float. Finally, what do you think makes more sense for the tokenizer to return when it encounters a -909? Should it return the SYMBOL - first, followed by the NUMBER 909 or should it return a NUMBER -909 right away?

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• Strategies for dealing with Circular references caused by JPA relationships?

  - by ams

  I am trying to partition my application into modules by features packaged into separate jars such as feature-a.jar, feature-b.jar, ... etc. Individual feature jars such as feature-a.jar should contain all the code for a feature a including jpa entities, business logic, rest apis, unit tests, integration test ... etc. The problem I am running into is that bi-directional relationships between JPA entities cause circular references between the jar files. For example Customer entity should be in customer.jar and the Order should be in order.jar but Customer references order and order references customer making it hard to split them into separate jars / eclipse projects. Options I see for dealing with the circular dependencies in JPA entities: Option 1: Put all the entities into one jar / one project Option 2: Don't map certain bi-directianl relationships to avoid circular dependencies across projects. Questions: What rules / principles have you used to decide when to do bi-directional mapping vs. not? Have you been able to break jpa entities into their own projects / jar by features if so how did you avoid the circular dependencies issues?

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• Coordinating typedefs and structs in std::multiset (C++)

  - by Sarah

  I'm not a professional programmer, so please don't hesitate to state the obvious. My goal is to use a std::multiset container (typedef EventMultiSet) called currentEvents to organize a list of structs, of type Event, and to have members of class Host occasionally add new Event structs to currentEvents. The structs are supposed to be sorted by one of their members, time. I am not sure how much of what I am trying to do is legal; the g++ compiler reports (in "Host.h") "error: 'EventMultiSet' has not been declared." Here's what I'm doing: // Event.h struct Event { public: bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } double time; int eventID; int hostID; }; // Host.h ... void calcLifeHist( double, EventMultiSet * ); // produces compiler error ... void addEvent( double, int, int, EventMultiSet * ); // produces compiler error // Host.cpp #include "Event.h" ... // main.cpp #include "Event.h" ... typedef std::multiset< Event, std::less< Event > > EventMultiSet; EventMultiSet currentEvents; EventMultiSet * cePtr = &currentEvents; ... Major questions Where should I include the EventMultiSet typedef? Are my EventMultiSet pointers obviously problematic? Is the compare function within my Event struct (in theory) okay? Thank you very much in advance.

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• Are certain open-source licenses more suitable than others for career growth?

  - by Francisco Garcia

  As a software engineer/programmer myself, I love the possibility to download the code and learn from it. However building software is what brings food to my table. I have doubts regarding the type of license I should use for my own personal projects or when picking up one project to learn from. There are already many questions about licenses on Stackoverflow, but I would like to make this one much more specific. If your main profession and way of living is building software: which type of license do you find more useful for you? And I mean, the license that can benefit you most as a professional because it gives you more freedom to reuse the experience you gain. GPL is a great license to build communities because it forces you to give back your work. However I like BSD licenses because of their extra freedom. I know that if the code I am exploring is BSD licensed, I might be able to expand not only my skills, but also my programmer toolbox. Whenever I am working for a company, I might recall that something similar was done in another project and I will be able to copy or imitate certain part of the code. I know that there are religious wars regarding GPL vs BSD and it is not my intention to start one. Probably many companies already take snipsets from GPL projects anyway. I just want to insist in the factor of professional enrichment. I do not intend to discriminate any license. I said I prefer BSD licenses but I also use Linux because the user base is bigger and also the market demand.

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• Good Replacement for User Control?

  - by David Lively

  I found user controls to be incredibly useful when working with ASP.NET webforms. By encapsulating the code required for displaying a control with the markup, creation of reusable components was very straightforward and very, very useful. While MVC provides convenient separation of concerns, this seems to break encapsulation (ie, you can add a control without adding or using its supporting code, leading to runtime errors). Having to modify a controller every time I add a control to a view seems to me to integrate concerns, not separate them. I'd rather break the purist MVC ideology than give up the benefits of reusable, packaged controls. I need to be able to include components similar to webforms user controls throughout a site, but not for the entire site, and not at a level that belongs in a master page. These components should have their own code not just markup (to interact with the business layer), and it would be great if the page controller didn't need to know about the control. Since MVC user controls don't have codebehind, I can't see a good way to do this. I've searched previous SO questions, and have yet to find a good answer. Options so far In an attempt to avoid turning the comments section into a discussion... RenderAction This allows the view to call another controller, which will be responsible for interacting with the BLL and whatever data is necessary to its corresponding view. The calling view needs to be aware of the sub controller. This seems to provide a nice way to encapsulate partial views and controls, without having to modify the calling controller. RenderPartial The calling controller is still responsible for executing whatever code is associated with the partial view, and making sure that the model passed to the partial view contains the data it expects. Effectively, modifying the partial view potentially means modifying the calling controller. Annoying especially if this is used in multiple places. Portable Areas Place each control in its own project/area?

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• Searching in graphs trees with Depth/Breadth first/A* algorithms

  - by devoured elysium

  I have a couple of questions about searching in graphs/trees: Let's assume I have an empty chess board and I want to move a pawn around from point A to B. A. When using depth first search or breadth first search must we use open and closed lists ? This is, a list that has all the elements to check, and other with all other elements that were already checked? Is it even possible to do it without having those lists? What about A*, does it need it? B. When using lists, after having found a solution, how can you get the sequence of states from A to B? I assume when you have items in the open and closed list, instead of just having the (x, y) states, you have an "extended state" formed with (x, y, parent_of_this_node) ? C. State A has 4 possible moves (right, left, up, down). If I do as first move left, should I let it in the next state come back to the original state? This, is, do the "right" move? If not, must I transverse the search tree every time to check which states I've been to? D. When I see a state in the tree where I've already been, should I just ignore it, as I know it's a dead end? I guess to do this I'd have to always keep the list of visited states, right? E. Is there any difference between search trees and graphs? Are they just different ways to look at the same thing?

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• MS Excel automation without macros in the generated reports. Any thoughts?

  - by ezeki77

  Hello! I know that the web is full of questions like this one, but I still haven't been able to apply the answers I can find to my situation. I realize there is VBA, but I always disliked having the program/macro living inside the Excel file, with the resulting bloat, security warnings, etc. I'm thinking along the lines of a VBScript that works on a set of Excel files while leaving them macro-free. Now, I've been able to "paint the first column blue" for all files in a directory following this approach, but I need to do more complex operations (charts, pivot tables, etc.), which would be much harder (impossible?) with VBScript than with VBA. For this specific example knowing how to remove all macros from all files after processing would be enough, but all suggestions are welcome. Any good references? Any advice on how to best approach external batch processing of Excel files will be appreciated. Thanks! PS: I eagerly tried Mark Hammond's great PyWin32 package, but the lack of documentation and interpreter feedback discouraged me.

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• entity framework insert bug

  - by tmfkmoney

  I found a previous question which seemed related but there's no resolution and it's 5 months old so I've opened my own version. http://stackoverflow.com/questions/1545583/entity-framework-inserting-new-entity-via-objectcontext-does-not-use-existing-e When I insert records into my database with the following it works fine for a while and then eventually it starts inserting null values in the referenced field. This typically happens after I do an update on my model from the database although not always after I do an update. I'm using a MySQL database for this. I have debugged the code and the values are being set properly before the save event. They're just not getting inserted properly. I can always fix this issue by re-creating the model without touching any of my code. I have to recreate the entire model, though. I can't just dump the relevant tables and re-add them. This makes me think it doesn't have anything to do with my code but something with the entity framework. Does anyone else have this problem and/or solved it? using (var db = new MyModel()) { var stocks = from record in query let ticker = record.Ticker select new { company = db.Companies.FirstOrDefault(c => c.ticker == ticker), price = Convert.ToDecimal(record.Price), date_stamp = Convert.ToDateTime(record.DateTime) }; foreach (var stock in stocks) { if (stock.company != null) { var price = new StockPrice { Company = stock.company, price = stock.price, date_stamp = stock.date_stamp }; db.AddToStockPrices(price); } } db.SaveChanges(); }

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• Inheritance and type parameters of Traversable

  - by Jesper

  I'm studying the source code of the Scala 2.8 collection classes. I have questions about the hierarchy of scala.collection.Traversable. Look at the following declarations: package scala.collection trait Traversable[+A] extends TraversableLike[A, Traversable[A]] with GenericTraversableTemplate[A, Traversable] trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] with TraversableOnce[A] package scala.collection.generic trait HasNewBuilder[+A, +Repr] trait GenericTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A] @uncheckedVariance] Question: Why does Traversable extend GenericTraversableTemplate with type parameters [A, Traversable] - why not [A, Traversable[A]]? I tried some experimenting with a small program with the same structure and got a strange error message when I tried to change it to Traversable[A]: error: Traversable[A] takes no type parameters, expected: one I guess that the use of the @uncheckedVariance annotation in GenericTraversableTemplate also has to do with this? (That seems like a kind of potentially unsafe hack to force things to work...). Question: When you look at the hierarchy, you see that Traversable inherits HasNewBuilder twice (once via TraversableLike and once via GenericTraversableTemplate), but with slightly different type parameters. How does this work exactly? Why don't the different type parameters cause an error?

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• how to keep the height of the div equal to the union of the height of elements inside it

  - by Idlecool

  I have been making a wordpress template. i got stuck at some place... the problem is, how to maintain the size of a div = the size of p tags and img tags... i have seen that the div only able to contain the p tag but the img tag over flows... i have my code in this following order: <div> <p> some contents <img src="an_image"/> some morecontent</p> <div> what i basically want is: div height = <p> height U(union) <img> height but, what actually i am getting is: div height = <p> height; while <img> over flows i have already checked for similar questions on Stack Overflow but was not able to find one which solves a similar problem.. please give me some idea..

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• Java-Hibernate: How can I translate these tables to hibernate annotations?

  - by penas

  I need to create a simple application using these tables: http://stackoverflow.com/questions/2612848/are-these-tables-respect-the-3nf-database-normalization I have created the application using simple old JDBC, but I would like to see how the application would look like using Hibernate, but I don't know how to put the sql code in java. I have found LOTS of examples, but I'm pretty much confused about using Hibernate and I don't know If I made such a good joob. For example, for the first three tables: AUTHOR table * Author_ID, PK * First_Name * Last_Name TITLES table * TITLE_ID, PK * NAME * Author_ID, FK DOMAIN table * DOMAIN_ID, PK * NAME * TITLE_ID, FK The code in java: Table 1 @Entity @Table(name = "AUTHORS", schema = "LIBRARY") public class Author{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "Author_ID") private int authorId; @Column(name = "First_Name", nullable = false, length = 50) private String firstName; @Column(name = "Last_Name", nullable = false, length = 40) private String lastName; @OneToMany @JoinColumn(name = "Title_ID") private List<Title> titles; Table 2 @Entity @Table(name = "TITLES") public class Title{ @Id @Column(name = "Title_ID") private int titleID; @Column(name = "Name", nullable = false, length = 50) private String name; @ManyToOne @JoinColumn(name = "Domain_ID") private Domain domains; Table 3 @Entity @Table(name = "DOMAINS") public class Domain{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "Domain_ID") private int Domain_ID; @Column(name = "Name", nullable = false, length = 50) private String name; @OneToOne(mappedBy = "domains") private Title title; } Any good? :)

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• How to determine loading status of images not attached to the DOM

  - by Rookwood

  I am working on a bit of javascript to plot data on a <canvas. The data points are marked by one of several different (small) image files. I am attempting to have the plot method wait until all the images are loaded. My best attempt thus far is such: var icon = { left : { air : new Image(), bone : new Image(), }, right : { air: new Image(), bone : new Image(), }, }; icon.left.air.src = option.imgPath + 'left.air.png'; icon.right.air.src = option.imgPath + 'right.air.png'; icon.left.bone.src = option.imgPath + 'left.bone.png'; icon.right.bone.src = option.imgPath + 'right.bone.png'; function main() { Canvas.draw(); // Make sure our image icons are loaded before we try to plot $(icon.left.air).load(function() { $(icon.right.air).load(function() { $(icon.left.bone).load(function() { $(icon.right.bone).load(function() { Data.plot(); }); }); }); }); } This works as expected most of the time. On occasion, it will fail and no data will be plotted. Inserting several console.log() statements shows that the script will silently stop working through the series of .load() statements, though code that comes after will be executed. My questions are as follows: Am I approaching this the right way? Is there a way to attach an event to my icon object that will fire once all of the images inside are loaded? This is a jquery plugin, so obviously jquery-based solutions are just as acceptable as vanilla javascript.

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• How to implement Administrator rights in Java Application?

  - by Yatendra Goel

  I am developing a Data Modeling Software that is implemented in Java. This application converts the textual data (stored in a database) to graphical form so that users can interpret the data in a more efficient form. Now, this application will be accessed by 3 kinds of persons: 1. Managers (who can fill the database with data and they can also view the visual form of the data after entering the data into the database) 2. Viewers (who can only view the visual form of data that has been filled by managers) 3. Administrators (who can create and manage other administrators, managers and viewers) Now, how to implement 3 diff. views of the same application. Note: Managers, Viewers and Administrators can be located in any part of the world and should access the application through internet. One idea that came in my mind is as follows: Step1: Code all the business logic in EJBs so that it can be used in distributed environment (means which can be accessed by several users through internet) Step2: Code 3 Swing GUI Clients: One for administrators, one for managers and one for viewers. These 3 GUI clients can access business logic written in EJBs. Step3: Distribute the clients corresponding to their users. For instance, manager client to managers. =================================QUESTIONS======================================= Q1. Is the above approach is correct? Q2. This is very common functionality that various softwares have. So, Do they implement this kind of functionality through this way or any other way? Q3. If any other approach would be more better, then what is that approach?

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• iPhone Development - calling external JSON API (will Apple reject?)

  - by RPM1984

  Ok guys, so im new to iPhone development, so apologies if this is a silly question, but before i actually create my app i want to know if this is possible, and if Apple will reject this. (Note this is all theoretical) So i'd have a API (.NET) that runs on a cloud server somewhere and can return HTML/JSON/XML. I'll have a website that can access this API and allow customers to do some stuff (but this is not important for this question). I would then like my iPhone app to make a call to this API which would return JSON data. So my iPhone app might make a call to http://myapp/Foos which would return a JSON string of Foo objects. The iPhone app would then parse this JSON and do some funky stuff with it. So, that's the background, now the questions: Is this possible? (that is, call an external cloud API over HTTP, parse JSON response?) What are the chances of Apple rejecting this application (because it would be calling a non-Apple API) Are there any limitations (security, libraries, etc) on the iPhone/Objective-C/Cocoa that might hinder this solution? On this website, they seem to be doing exactly what im asking. Thoughts, suggestions, links would be greatly appreciated...

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• Can't understand sessions in Rails

  - by ciss

  Hello everyone. Please don't bit my for my misunderstanding. The sessions are very new for me, and i have some problems. Okay i read many information about sessions and especially rails session. But this don't give me right imagine about sessions. Did i understand right, when users send request to server (get) - Server create a new session (and store this some file in hard drive with session id), session id - is a random generated num? so, server create a new session (and store session on drive) after this server send back answer to client and set session_id in cookies? Ok, i debug some params and see some results: debug(session): {:_csrf_token=>"jeONIfNxFmnpDn/xt6I0icNK1m3EB3CzT9KMntNk7KU=", :session_id=>"06c5628155efaa6446582c491499af6d", "flash"=>{}} debug(cookies): {"remember_user_token"=>"1::3GFRFyXb83lffzwPDPQd", "_blog_session"=>"BAh7CDoQX2NzcmZfdG9rZW4iMWplT05JZk54Rm1ucERuL3h0NkkwaWNOSzFtM0VCM0N6VDlLTW50Tms3S1U9Og9zZXNzaW9uX2lkIiUwNmM1NjI4MTU1ZWZhYTY0NDY1ODJjNDkxNDk5YWY2ZCIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA==--348c88b594e98f4bf6389d94383134fbe9b03095"} Okay, i know, what _csrf_token helps to prevent csrf. session_id - is id of the session which stored on hard drive (by default) but what is _blog_session in cookies? also, remeber_user_token containes my id (1::*) and what about second part, what is it? Sorry for this stupid questions, i know what i can easy use any nice auth-plugins (authlogic/clearance/devise), but i want to fully understand sessions. Thank you. (also sorry for my english, this is not my native language)

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• Nested Data XML design

  - by esryl

  Looking to nest (to unlimited levels) elements in XML. Like so: <items> <item> <name>Item One</name> <item> <name>Item Two</name> </item> <item> <name>Item Three</name> <item> <name>Item Four</name> </item> <!-- etc... --> </item> </item> </items> However. While browsing for a solution I noticed in the comments of: http://stackoverflow.com/questions/988139/weird-nesting-in-xml while the above is well formed it would not validate against any sinsible DTD. Two things, what is a better way of nesting similar elements, and secondly what would be the design of the DTD. UPDATE: Would prefer to validate against an XML Schema rather than DTD.

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• Stop Visual Studio from appending numbers to the end of new controls

  - by techturtle

  I am wondering if there is any way to stop Visual Studio 2010 from appending a number to the end of the ID on new controls I create. For example, when I add a new TextBox, I would prefer that it do this: <asp:TextBox ID="TextBox" runat="server"> <asp:TextBox ID="TextBox" runat="server"> <asp:TextBox ID="TextBox" runat="server"> Instead of this: <asp:TextBox ID="TextBox1" runat="server"> <asp:TextBox ID="TextBox2" runat="server"> <asp:TextBox ID="TextBox3" runat="server"> It would make it easier to rename them appropriately, so I don't have to arrow/mouse over and delete the number each time. As I was writing this, the "Questions that may already have your answer" suggested this: How do I prevent Visual Studio from renaming my controls? which admittedly was the biggest part of my annoyance, but that appears to turn off putting in an ID="" field altogether, not just for pasted controls. It would still be helpful to turn off the numbering for new, non-pasted controls and have it not rename pasted ones as well. At the moment I'm working with ASP.NET, but it would be nice if it there was a way to do it for WinForms as well. Before anyone suggests it, I do know that allowing it to append the numbers prevents name conflicts should I not rename them appropriately. However, I would much rather have it fail to compile so I know to fix the issue now (if I forget to name something properly) rather than find random "TextBox1" items lying around in the code later on.

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• How to select LI exept first and second ?

  - by Wazdesign

  Here is the structure of the content , I want to select all LI except the first two ( ie no-link) jQuery(document).ready(function(){ var nosubnav = jQuery('.first-level li:not(:has(ul))'); var nosubnavsize = jQuery('.first-level li:not(:has(ul))').size(); jQuery(nosubnav).css('border' , '1px solid red'); alert('List item which does not have submenu '+nosubnavsize); }); div class="navigation-container"> <ul class="first-level"> <li><a href="#">No Link</a></li> <li><a href="#">No Link</a></li> <li><a href="#">Link 1</a></li> <li><a href="#">Link 2</a> <ul> <li><a href="#">Link2.1</a></li> <li><a href="#">Link2.2</a> <ul> <li><a href="#">Link 2.2.1</a></li> </ul> </li> </ul> </li> <li><a href="#">Link </a></li> </ul> </div> related Question : http://stackoverflow.com/questions/2771801/how-to-count-li-which-does-not-have-ul

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• Why does Ruby have Rails while Python has no central framework?

  - by yar

  This is a(n) historical question, not a comparison-between-languages question: This article from 2005 talks about the lack of a single, central framework for Python. For Ruby, this framework is clearly Rails. Why, historically speaking, did this happen for Ruby but not for Python? (or did it happen, and that framework is Django?) Also, the hypothetical questions: would Python be more popular if it had one, good framework? Would Ruby be less popular if it had no central framework? [Please avoid discussions of whether Ruby or Python is better, which is just too open-ended to answer.] Edit: Though I thought this is obvious, I'm not saying that other frameworks do not exist for Ruby, but rather that the big one in terms of popularity is Rails. Also, I should mention that I'm not saying that frameworks for Python are not as good (or better than) Rails. Every framework has its pros and cons, but Rails seems to, as Ben Blank says in the one of the comments below, have surpassed Ruby in terms of popularity. There are no examples of that on the Python side. WHY? That's the question.

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• Queuing using table or MSMQ?

  - by Lieven Cardoen

  A part of the application I'm working on is an swf that shows a test with some 80 questions. Each question is saved to a sql server through WebORB and asp.net. If a candidate finisheds the test, the session needs to be validated. Problem now is that sometimes 350 candidates finish their test at the same moment, and cpu on webserver and sql server explodes (350 validations concurrently). Now, how would I implement queuing here? In the database, there's a table that has a record for each session. One column holds the status. 1 is finished, 2 is validated. I could implement queuing in two ways (as I see it, maybe you have other propositions): A process that checks the table for records with status 1. If it finds one, it validates the session. So, sessions are validated one after one. If a candidate finishes its session, a message is sent to a MSMQ queue. Another process listens to the queue and validates sessions one after one. Now, What would be the best approach? Where do you start the process that will validate sessions? In your global.asax (application_start)? As a windows service? As an exe on the root of the website that is started in application_start? To me, using the table and looking for records with status 1 seems the easiest way.

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• in Rails, with check_box_tag, how do I keep the checkboxes checked after submitting query?

  - by Sebastien Paquet

  Ok, I know this is for the Saas course and people have been asking questions related to that as well but i've spent a lot of time trying and reading and I'm stuck. First of all, When you have a model called Movie, is it better to use Ratings as a model and associate them or just keep Ratings in an array floating in space(!). Second, here's what I have now in my controller: def index @movies = Movie.where(params[:ratings].present? ? {:rating => (params[:ratings].keys)} : {}).order(params[:sort]) @sort = params[:sort] @ratings = Ratings.all end Now, I decided to create a Ratings model since I thought It would be better. Here's my view: = form_tag movies_path, :method => :get do Include: - @ratings.each do |rating| = rating.rating = check_box_tag "ratings[#{rating.rating}]" = submit_tag "Refresh" I tried everything that is related to using a conditional ternary inside the checkbox tag ending with " .include?(rating) ? true : "" I tried everything that's supposed to work but it doesn't. I don't want the exact answer, I just need guidance.Thanks in advance!

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• Ubuntu + virtualenv = a mess? virtualenv hates dist-packages, wants site-packages

  - by lostincode

  Can someone please explain to me what is going on with python in ubuntu 9.04? I'm trying to spin up virtualenv, and the --no-site-packages flag seems to do nothing with ubuntu. I installed virtualenv 1.3.3 with easy_install (which I've upgraded to setuptools 0.6c9) and everything seems to be installed to /usr/local/lib/python2.6/dist-packages I assume that when installing a package using apt-get, it's placed in /usr/lib/python2.6/dist-packages/ ? The issue is, there is a /usr/local/lib/python2.6/site-packages as well that just sits there being empty. It would seem (by looking at the path in a virtualenv) that this is the folder virtualenv uses as backup. Thus even thought I omit --no-site-packages, I cant access my local systems packages from any of my virtualenv's. So my questions are: How do I get virtualenv to point to one of the dist-packages? Which dist-packages should I point it to? /usr/lib/python2.6/dist-packages or /usr/local/lib/python2.6/dist-packages/ What is the point of /usr/lib/python2.6/site-packages? There's nothing in there! Is it first come first serve on the path? If I have a newer version of package XYZ installed in /usr/local/lib/python2.6/dist-packages/ and and older one (from ubuntu repos/apt-get) in /usr/lib/python2.6/dist-packages, which one gets imported when I import xyz? I'm assuming this is based on the path list, yes? Why the hell is this so confusing? Is there something I'm missing here? Where is it defined that easy_install should install to /usr/local/lib/python2.6/dist-packages? Will this affect pip as well? Thanks to anyone who can clear this up!

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• Set a datetime for next or previous sunday at specific time

  - by Marc

  I have an app where there is always a current contest (defined by start_date and end_date datetime). I have the following code in the application_controller.rb as a before_filter. def load_contest @contest_last = Contest.last @contest_last.present? ? @contest_leftover = (@contest_last.end_date.utc - Time.now.utc).to_i : @contest_leftover = 0 if @contest_last.nil? Contest.create(:start_date => Time.now.utc, :end_date => Time.now.utc + 10.minutes) elsif @contest_leftover < 0 @winner = Organization.order('votes_count DESC').first @contest_last.update_attributes!(:organization_id => @winner.id, :winner_votes => @winner.votes_count) if @winner.present? Organization.update_all(:votes_count => 0) Contest.create(:start_date => @contest_last.end_date.utc, :end_date => Time.now.utc + 10.minutes) end end My questions: 1) I would like to change the :end_date to something that signifies next Sunday at a certain time (eg. next Sunday at 8pm). Similarly, I could then set the :start_date to to the previous Sunday at a certain time. I saw that there is a sunday() class (http://api.rubyonrails.org/classes/Time.html#method-i-sunday), but not sure how to specify a certain time on that day. 2) For this situation of always wanting the current contest, is there a better way of loading it in the app? Would caching it be better and then reloading if a new one is created? Not sure how this would be done, but seems to be more efficient. Thanks!

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• How to limit setAccessible to only "legitimate" uses?

  - by polygenelubricants

  The more I learned about the power of setAccessible, the more astonished I am at what it can do. This is adapted from my answer to the question (Using reflection to change static final File.separatorChar for unit testing). import java.lang.reflect.*; public class EverythingIsTrue { static void setFinalStatic(Field field, Object newValue) throws Exception { field.setAccessible(true); Field modifiersField = Field.class.getDeclaredField("modifiers"); modifiersField.setAccessible(true); modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL); field.set(null, newValue); } public static void main(String args[]) throws Exception { setFinalStatic(Boolean.class.getField("FALSE"), true); System.out.format("Everything is %s", false); // "Everything is true" } } You can do truly outrageous stuff: public class UltimateAnswerToEverything { static Integer[] ultimateAnswer() { Integer[] ret = new Integer[256]; java.util.Arrays.fill(ret, 42); return ret; } public static void main(String args[]) throws Exception { EverythingIsTrue.setFinalStatic( Class.forName("java.lang.Integer$IntegerCache") .getDeclaredField("cache"), ultimateAnswer() ); System.out.format("6 * 9 = %d", 6 * 9); // "6 * 9 = 42" } } Presumably the API designers realize how abusable setAccessible can be, but must have conceded that it has legitimate uses to provide it. So my questions are: What are the truly legitimate uses for setAccessible? Could Java has been designed as to NOT have this need in the first place? What would the negative consequences (if any) of such design be? Can you restrict setAccessible to legitimate uses only? Is it only through SecurityManager? How does it work? Whitelist/blacklist, granularity, etc? Is it common to have to configure it in your applications?

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• How to convert Big Endian and how to flip the highest bit?

  - by Robert Frank

  I am using a TStream to read binary data (thanks to this post: http://stackoverflow.com/questions/2878180/how-to-use-a-tfilestream-to-read-2d-matrices-into-dynamic-array). My next problem is that the data is Big Endian. From my reading, the Swap() method is seemingly deprecated. How would I swap the types below? 16-bit two's complement binary integer 32-bit two's complement binary integer 64-bit two's complement binary integer IEEE single precision floating-point - Are IEEE affected by Big Endian? And, finally, since the data is unsigned, the creators of this dataset have stored the unsigned values as signed integers (excluding the IEEE). They instruct that one need only add an offset (2^15, 2^31, and 2^63) to recover the unsigned data. But, they note that flipping the most significant bit is the fastest way to do that. How does one efficiently flip the most significant bit of a 16, 32, or 64-bit integer? So, if the data on disk (16-bit) is "85 FB" - the desired result after reading the data and swapping and bit flipping would be 1531. Is there a way to accomplish the swapping and bit flipping with generics so it fits into the generic answer at the link above? Yes, kids, THIS is how scientific astronomical data is stored by NASA, ESO, and all professional astronomers. This FITS standard is considered by some to be one of the most successful standards ever created in its proliferation and flexibility!

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