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• How to restrict text search to a certain subset of the database ?

  - by Nikhil Garg

  I have a large central database of around 1 million heavy records. In my app, for every user I would have a subset of rows from central table, which would be very small (probably 100 records each).When a particular user has logged in , I would want to search on this data set only. Example: Say I have a central database of all cars in the world. I have a user profile for General Motors(GM) , Ferrari etc. When GM is logged in I just want to search(a full text search and not fire a sql query) for those cars which are manufactured by GM. Also GM may launch/withdraw a model in which case central db would be updated & so would be rowset associated with GM. In case of acquisitions, db of certain profiles may change without launch/removal of new car. So central db wont change then , but rowsets may. Whats the best way to implement such a design ? These smaller row sets would need to be dynamic depending on user activities. We are on Rails 2.3.5 and use thinking_sphinx as the connector and Sphinx/MySQL for search and relational associations.

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• Do I need Response.End() in ASP.Net 2.0

  - by Hamish Grubijan

  Hi, I am just starting with ASP.Net. I copied a ex-co-worker's code (from .Net 1.1 era) and it has a Response.End(); in case of an error. There is also a: catch (Exception ex) { Response.Write(ex.Message); Response.End(); } at the end of Page_Load(object sender, System.EventArgs e) which always appends "Thread was aborted." or something like that at the end. I suspect that this worked differently before, or the error conditions were not tested very well. Anyhow, I was able to stop using Response.End(); in case when I do not like the GET parameters, and use return; instead. It seemed to do the right think in a simple case. Is this Ok in general? There are some problems with the code I copied, but I do not want to do a rewrite; I just want to get it running first and find wrinkles later. The Response.End(); caused a mental block for me, however, so I want to figure it out. I want to keep the catch all clause just in case, at least for now. I could also end the method with: catch (System.Threading.ThreadAbortException) { Response.End(); } catch (Exception ex) { Response.Write(ex.Message); Response.End(); } but that just seems extremely stupid, once you think about all of the exceptions being generated. Please give me a few words of wisdom. Feel free to ask if something is not clear. Thanks! P.S. Ex-coworker was not fired and is a good coder - one more reason to reuse his example.

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• Passing data between ViewControllers versus doing local Fetch in each VC

  - by Tofrizer

  Hi All, I'm developing an iPhone app using Core Data and I'm looking for some general advice and recommendations on whether its acceptable to pass data between ViewControllers versus doing a local fetch in each ViewController as you navigate to it. Ordinarily I would say it all depends on various factors (e.g. performance etc) but the passing data approach is so prevalent in my app and I'm spooked by all the stories about Apple rejecting apps because of not conforming to their standard guidelines. So let me put another way -- is it non-standard to pass data between VC's? The reason I pass data so much is because each ViewController is just another view on to data present in my object model / graph. Once I have a handle on my first object in the first view controller (which I of course do have to fetch), I can use the existing object composition / relationships to drill down into the next level of detail into data and so I just pass these objects to the next VC. Separately, one possible downside with this passing-data-to-each-VC approach is I don't benefit from (what I perceive to be) the optimisation/benefits that NSFetchedResultsController provides in terms of efficient memory usage and section handling. My app is read-only but I do have one table with 5000 rows and I'm curious if I am missing out on NSFetchedResultsController benefits. Any thoughts on this as well? Can I somehow still benefit from NSFetchedResultsController goodness without having to do a full fetch (as I would have already passed in the data from my previous VC)? Thanks a lot.

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• Targeted Simplify in Mathematica

  - by Timo

  I generate very long and complex analytic expressions of the general form: (...something not so complex...)(...ditto...)(...ditto...)...lots... When I try to use Simplify, Mathematica grinds to a halt, I am assuming due to the fact that it tries to expand the brackets and or simplify across different brackets. The brackets, while containing long expressions, are easily simplified by Mathematica on their own. Is there some way I can limit the scope of Simplify to a single bracket at a time? Edit: Some additional info and progress. So using the advice from you guys I have now started using something in the vein of In[1]:= trouble = Log[(x + I y) (x - I y) + Sqrt[(a + I b) (a - I b)]]; In[2]:= Replace[trouble, form_ /; (Head[form] == Times) :> Simplify[form],{3}] Out[2]= Log[Sqrt[a^2 + b^2] + (x - I y) (x + I y)] Changing Times to an appropriate head like Plus or Power makes it possible to target the simplification quite accurately. The problem / question that remains, though, is the following: Simplify will still descend deeper than the level specified to Replace, e.g. In[3]:= Replace[trouble, form_ /; (Head[form] == Plus) :> Simplify[form], {1}] Out[3]= Log[Sqrt[a^2 + b^2] + x^2 + y^2] simplifies the square root as well. My plan was to iteratively use Replace from the bottom up one level at a time, but this clearly will result in vast amount of repeated work by Simplify and ultimately result in the exact same bogging down of Mathematica I experienced in the outset. Is there a way to restrict Simplify to a certain level(s)? I realize that this sort of restriction may not produce optimal results, but the idea here is getting something that is "good enough".

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• Enforce strong type checking in C (type strictness for typedefs)

  - by quinmars

  Is there a way to enforce explicit cast for typedefs of the same type? I've to deal with utf8 and sometimes I get confused with the indices for the character count and the byte count. So it be nice to have some typedefs: typedef unsigned int char_idx_t; typedef unsigned int byte_idx_t; With the addition that you need an explicit cast between them: char_idx_t a = 0; byte_idx_t b; b = a; // compile warning b = (byte_idx_t) a; // ok I know that such a feature doesn't exist in C, but maybe you know a trick or a compiler extension (preferable gcc) that does that. EDIT: I still don't really like the Hungarian notation in general, I couldn't used it for this problem because of project coding conventions, but I used it now in another similar case, where also the types are the same and the meanings are very similar. And I have to admit: it helps. I never would go and declare every integer with a starting "i", but as in Joel's example for overlapping types, it can be life saving.

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• MS Query Analizer/Management Studio replacement?

  - by kprobst

  I've been using SQL Server since version 6.5 and I've always been a bit amazed at the fact that the tools seem to be targeted to DBAs rather than developers. I liked the simplicity and speed of the Query Analizer for example, but hated the built-in editor, which was really no better than a syntax coloring-capable Notepad. Now that we have Management Studio the management part seems a bit better but from a developer standpoint the tools is even worse. Visual Studio's excellent text editor... without a way to customize keyboard bindings!? Don't get me started on how unusable is the tree-based management hierarchy. Why can't I re-root the tree on a list of stored procs for example the way the Enterprise Manager used to allow? Now I have a treeview that needs to be scrolled horizontally, which makes it eminently useless. The SQL server support in Visual Studio is fantastic for working with stored procedures and functions, but it's terrible as a general ad hoc data query tool. I've tried various tools over the years but invariably they seem to focus on the management side and shortchange the developer in me. I just want something with basic admin capabilities, good keyboard support and requisite DDL functionality (ideally something like the Query Analyzer). At this point I'm seriously thinking of using vim+sqlcmd and a console... I'm that desperate :) Those of you who work day in and day out with SQL Server and Visual Studio... do you find the tools to be adequate? Have you ever wished they were better and if you have found something better, could you share please? Thanks!

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• libav/ffmpeg: avcodec_decode_video2() returns -1 when separating demultiplexing and decoding

  - by unbekannt

  I'm using libav (from a C++ program on Linux and Windows) to decode video streams from a file, which works fine (decoding various formats like H264 and MPEG2) using avformat_open_input(), av_read_frame() and avcodec_decode_video2(). Now I have to separate demultiplexing and decoding. One class will call avformat_open_input() and av_read_frame() and then pass the AVPackets into a queue that is read by another class. There I use avcodec_alloc_context3() to get the AVCodecContext needed for avcodec_decode_video2(). I've tested that with a MPEG2 video stream and it works. Problems arise if I try to decode a H264 stream: avcodec_decode_video2() always returns -1 and outputs "no frame". I understand that additional data (SPS/PPS) is needed to decode this stream, so I've tried to replicate the original AVCodecContext from the demultiplexer in the decoder, but it won't work: Copying the content of the extradata field and setting all other values that differ from the default ones in the decoder: -1 is returned Using the same context (i.e. passing along the pointer) results in a crash I also tried to set CODEC_FLAG2_CHUNKS. avcodec_decode_video2() then always returns packet.size - 3 (??) and frameFinished is never set to 1. In my opinion I have a general problem here that will arise whenever settings from the original CodecContext are needed to decode the AVPackets. I'd be grateful for any hints on how to solve that problem!

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• Working around "one executable per project" in Visual C# for many small test programs

  - by Kevin Ivarsen

  When working with Visual Studio in general (or Visual C# Express in my particular case), it looks like each project can be configured to produce only one output - e.g. a single executable or a library. I'm working on a project that consists of a shared library and a few application, and I already have one project in my solution for each of those. However, during development I find it useful to write small example programs that can run one small subsystem in isolation (at a level that doesn't belong in the unit tests). Is there a good way to handle this in Visual Studio? I'd like to avoid adding several dozen separate projects to my solution for each small test program I write, especially when these programs will typically be less than 100 lines of code. I'm hoping to find something that lets me continue to work in Visual Studio and use its build system (rather than moving to something like NAnt). I could foresee the answer being something like: A way of setting this up in Visual Studio that I haven't found yet A GUI like NUnit's graphical runner that searches an assembly for classes with defined Main() functions that you can select and run A command line tool that lets you specify an assembly and a class with a Main function to run

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• How to use an Audio Unit on the iPhone

  - by CodeToaster

  I'm looking for a way to change the pitch of recorded audio as it is saved to disk, or played back (in real time). I understand Audio Units can be used for this. The iPhone offers limited support for Audio Units (for example it's not possible to create/use custom audio units, as far as I can tell), but several out-of-the-box audio units are available, one of which is AUPitch. How exactly would I use an audio unit (specifically AUPitch)? Do you hook it into an audio queue somehow? Is it possible to chain audio units together (for example, to simultaneously add an echo effect and a change in pitch)? EDIT: After inspecting the iPhone SDK headers (I think AudioUnit.h, I'm not in front of a Mac at the moment), I noticed that AUPitch is commented out. So it doesn't look like AUPitch is available on the iPhone after all. weep weep Apple seems to have better organized their iPhone SDK documentation at developer.apple.com of late - now its more difficult to find references to AUPitch, etc. That said, I'm still interested in quality answers on using Audio Units (in general) on the iPhone.

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• Minimum cost strongly connected digraph

  - by Kazoom

  I have a digraph which is strongly connected (i.e. there is a path from i to j and j to i for each pair of nodes (i, j) in the graph G). I wish to find a strongly connected graph out of this graph such that the sum of all edges is the least. To put it differently, I need to get rid of edges in such a way that after removing them, the graph will still be strongly connected and of least cost for the sum of edges. I think it's an NP hard problem. I'm looking for an optimal solution, not approximation, for a small set of data like 20 nodes. Edit A more general description: Given a grap G(V,E) find a graph G'(V,E') such that if there exists a path from v1 to v2 in G than there also exists a path between v1 and v2 in G' and sum of each ei in E' is the least possible. so its similar to finding a minimum equivalent graph, only here we want to minimize the sum of edge weights rather than sum of edges. Edit: My approach so far: I thought of solving it using TSP with multiple visits, but it is not correct. My goal here is to cover each city but using a minimum cost path. So, it's more like the cover set problem, I guess, but I'm not exactly sure. I'm required to cover each and every city using paths whose total cost is minimum, so visiting already visited paths multiple times does not add to the cost.

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• JSON VIEW using GROUP_CONCAT question

  - by Dan Beam

  Hey DBAs and overall smart dudes. I have a question for you. We use MySQL VIEWs to format our data as JSON when it's returned (as a BLOB), which is convenient (though not particularly nice on performance, but we already know this). But, I can't seem to get a particular query working right now (each row contains NULL when it should contain a created JSON object with the values of multiple JOINs). Here's the general idea: SELECT CONCAT( "{", "\"some_list\":[", GROUP_CONCAT( DISTINCT t1.id ), "],", "\"other_list\":[", GROUP_CONCAT( DISTINCT t2.id ), "],", "}" ) cool_json FROM table_name tn INNER JOIN ( some_table st ) ON st.some_id = tn.id LEFT JOIN ( another_table at, another_one ao, used_multiple_times t1 ) ON st.id = at.some_id AND at.different_id = ao.different_id AND ao.different_id = t1.id LEFT JOIN ( another_table2 at2, another_one2 ao2, used_multiple_times t2 ) ON st.id = at2.some_id AND at2.different_id = ao2.different_id AND ao2.different_id = t2.id GROUP BY tn.id ORDER BY tn.name Anybody know the problem here? Am I missing something I should be grouping by? It was working when I was only doing 1 LEFT JOIN & GROUP_CONCAT, but now with multiple JOINs / GROUP_CONCATs it's messing it up. When I move the GROUP_CONCATs from the "cool_json" field they work as expected, but I'd like my data formatted as JSON so I can decode it server-side or client-side in one step.

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• C++ : Avoid lot of boolean variable for multiple verification conditions in trading app

  - by Naveen

  Hi i am a junior dev in trading app... we have a order refresh verification unit. It has to verify order confirmation from exchange. We send a bunch of different request in bulk ( NEW, MODIFY, CANCEL ) to exchange... Verification has to happen for max N times with each T intervals for all orders. if verification successful for all the order before N retry then fine.. otherwise we need to indicate as verification unsuccessfull. i hv done a basic coding done in very urgent like below for( N times ) { for_each ( sent_request_order ) // SENT { 1) get all the refreshed order from DB or shared mem i.e REFRESHED 2) find current sent order in REFRESHED if( not_found ) not refreshed from exchange, continue to next order if( found ) case NEW : //check for new status, mark verification done case MODIFY : //check for modified status.. //if not mark pending, go to next order, //revisit the same after T time case CANCEL : //check for cancelled status.. //if not mark pending, go to next order, //revisit the same after T time } if( all_verified ) exit from verification. wait ( T sec ) } order_verification_pending, order_verification_done, order_visited, order_not_visited, all_verified, all_not_verified ... lot of boolean flags used for indication.. is there any better approach for doing this.... splitting responsibilities across the classes......???? i know this is not a general question.... but still flags are making me tidious to handle...

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• How to detect a WCF session crash before calling a contract method?

  - by brain_pusher

  I am using a session mode for my WCF service. The problem is the following: if session is broken and no longer exists, client can't know it before calling a contract. For example, if the service has been restarted, the client's session id is invalid, because that session has been closed on the server side. I check the channel state before calling the contract and its value is CommunicationState.Opened even if session is already broken. So, when I call the contract after this check I get a CommunicationException with this message: The remote endpoint no longer recognizes this sequence. This is most likely due to an abort on the remote endpoint. The value of wsrm:Identifier is not a known Sequence identifier. The reliable session was faulted. Is there any workaround? I need a way to get an appropriate session state before calling a contract so that I can restore it without getting an exception. P.S. The CommunicationException type is general, so I can't detect a session crash by catching this exception. P.P.S. I have asked the similar question here, but in that case I didn't know the reason, now I don't know how to evade it.

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• How should I generate the partitions / pairs for the Chinese Postman problem?

  - by Simucal

  I'm working on a program for class that involves solving the Chinese Postman problem. Our assignment only requires us to write a program to solve it for a hard-coded graph but I'm attempting to solve it for the general case on my own. The part that is giving me trouble is generating the partitions of pairings for the odd vertices. For example, if I had the following labeled odd verticies in a graph: 1 2 3 4 5 6 I need to find all the possible pairings / partitions I can make with these vertices. I've figured out I'll have i paritions given: n = num of odd verticies k = n / 2 i = ((2k)(2k-1)(2k-2)...(k+1))/2 So, given the 6 odd verticies above, we will know that we need to generate i = 15 partitions. The 15 partions would look like: 1 2 3 4 5 6 1 2 3 5 4 6 1 2 3 6 4 5 ... 1 6 ... Then, for each partition, I take each pair and find the shortest distance between them and sum them for that partition. The partition with the total smallest distance between its pairs is selected, and I then double all the edges between the shortest path between the odd vertices (found in the selected partition). These represent the edges the postman will have to walk twice. At first I thought I had worked out an appropriate algorithm for generating these partitions / pairs but it is flawed. I found it wasn't a simple permutation/combination problem. Does anyone who has studied this problem before have any tips that can help point me in the right direction for generating these partitions?

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• Customizing orchard theme parts

  - by madcapnmckay

  Hi, I am trying to write a custom theme for orchard and am not having much success so far. I have read Bertrand Le Roy's article on part alternates but I can't seem to get it to work. I am displaying a list of recent blog posts on the front page, pretty standard. I wish to change the markup produced by the meta data part i.e the time format. I have written a IShapeTableProvider to create blog specific alternates for the metadata summary part. public class MetaDataShapeProvider : IShapeTableProvider { private readonly IWorkContextAccessor workContextAccessor; public MetaDataShapeProvider(IWorkContextAccessor workContextAccessor) { this.workContextAccessor = workContextAccessor; } public void Discover(ShapeTableBuilder builder) { builder .Describe("Parts_Common_Metadata_Summary") .OnDisplaying(displaying => { ContentItem contentItem = displaying.Shape.ContentItem; if (contentItem != null) displaying.ShapeMetadata.Alternates.Add("Metadata__" + contentItem.ContentType); }); } } This is being caught correctly but the contentItem is null. Should I just create an alternate with a fixed name like "Metadata-BlogPost" and use that, to make this general purpose it should really be a dynamic name so I can use another alternate template elsewhere. Thanks, Ian

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• Using nohup mysqldump from php script is inserting a '!' and breaking to a new line.

  - by Aglystas

  I'm trying to run a mysqldump from php using the nohup command to prevent the script from hanging. Here's the command (The database is mc6_erik_test, everything else is just a table list until you get to the end) exec("mysqldump -u root -pPassword -h vfmy1-dev.mountainmedia.com mc6_erik_test access_log admin affiliate affiliate_2_product authorized_ip category category_2_product claim_code claim_code_log country_exclude customer customer_2_subscription customer_account_log customer_address customer_bill customer_discount customer_ip customer_key email_bulk_log email_draft email_queue email_queue_log email_template endicia_log gift_wrap image_bulk_upload log mailing_list manufacturer merchant merchant_checkout merchant_ip merchant_ship merchant_ship_conf new_account_temp order_dest order_item order_item_2_dest order_item_2_package order_item_log order_item_registrant order_note order_package order_package_label orders package package_2_product pref product product_2_supplier product_also product_event_date product_image product_option product_related product_review product_review_helpful product_ship_disable report search_log subscription supplier temp_product transaction_account transactions wish_list wish_list_fill wish_list_item --opt --where='merchant_id=\'6\'' /tmp/sync_db_card_20100519105358.sql"); As you can see it's really long, because I have to specifically include only the tables I want to dump. The command works great from the command line, however when I run it through a web script towards the end the following is being used as the command... supplier temp_product transaction_account transactio! ns wish_list wish_list_fill wish_list_item --opt --where='merchant_id="6"' > /tmp/sync_db_card_20100519105358.sql So the table 'transactions' is being split by an exclamation point and newline. The rest of the command is exactly the same. And if I run this through the php-cli interface it doesn't happen only when I try running it via the webserver using nohup. I'm wondering if there is some inherit string length to using the exec command within a php script, or really if anyone has any general idea what is going on here.

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• Efficient Clojure workflow?

  - by Alex B

  I am developing a pet project with Clojure, but wonder if I can speed up my workflow a bit. My current workflow (with Compojure) is: Start Swank with lein swank. Go to Emacs, connect with M-x slime-connect. Load all existing source files one by one. This also starts a Jetty server and an application. Write some code in REPL. When satisfied with experiments, write a full version of a construct I had in mind. Eval (C-c C-c) it. Switch REPL to namespace where this construct resides and test it. Switch to browser and reload browser tab with the affected page. Tweak the code, eval it, check in the browser. Repeat any of the above. There are a number of annoyances with it: I have to switch between Emacs and the browser (or browsers if I am testing things like templating with multiple browsers) all the time. Is there a common idiom to automate this? I used to have a JavaScript bit that reloads the page continuously, but it's of limited utility, obviously, when I have to interact with the page for more than a few seconds. My JVM instance becomes "dirty" when I experiment and write test functions. Basically namespaces become polluted, especially if I'm refactoring and moving the functions between namespaces. This can lead to symbol collisions and I need to restart Swank. Can I undef a symbol? I load all source files one by one (C-c C-k) upon restarting Swank. I suspect I'm doing it all wrong. Switching between the REPL and the file editor can be a bit irritating, especially when I have a lot of Emacs tabs open, alongside the browser(s). I'm looking for ways to improve the above points and the entire workflow in general, so I'd appreciate if you'd share yours. P. S. I have also used Vimclojure before, so Vimclojure-based workflows are welcome too.

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• How do tools like Hiphop for PHP deal with heterogenous arrays?

  - by Derek Thurn

  I think HipHop for PHP is an interesting tool. It essentially converts PHP code into C++ code. Cross compiling in this manner seems like a great idea, but I have to wonder, how do they overcome the fundamental differences between the two type systems? One specific example of my general question is heterogeneous data structures. Statically typed languages don't tend to let you put arbitrary types into an array or other container because they need to be able to figure out the types on the other end. If I have a PHP array like this: $mixedBag = array("cat", 42, 8.5, false); How can this be represented in C++ code? One option would be to use void pointers (or the superior version, boost::any), but then you need to cast when you take stuff back out of the array... and I'm not at all convinced that the type inferencer can always figure out what to cast to at the other end. A better option, perhaps, would be something more like a union (or boost::variant), but then you need to enumerate all possible types at compile time... maybe possible, but certainly messy since arrays can contain arbitrarily complex entities. Does anyone know how HipHop and similar tools which go from a dynamic typing discipline to a static discipline handle these types of problems?

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• Should I write more SQL to be more efficient, or less SQL to be less buggy?

  - by RenderIn

  I've been writing a lot of one-off SQL queries to return exactly what a certain page needs and no more. I could reuse existing queries and issue a number of SQL requests linear to the number of records on the page. As an example, I have a query to return People and a query to return Job Details for a person. To return a list of people with their job details I could query once for people and then once for each person to retrieve their job details. I've found that in most cases that solution returns things in a reasonable amount of time, but I don't know how well it will scale in my environment. Instead I've been writing queries to join people + job details, or people + salary history, etc. I'm looking at my models and I see how I could shave off maybe 30% of my code if I were to re-use existing queries. This is a big temptation. Is it a bad thing to go for reuse over efficiency in general or does it all come down to the specific situation? Should I first do it the easy way and then optimize later, or is it best to get the code knocked out while everything is fresh in my mind? Thoughts, experiences?

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• compiling and running java on windows

  - by artur grzesiak

  I thought the task should be fairly easy, but my understanding of javac and java in general is rather poor. I am using Windows8 and would like to compile a single file.java that makes use of other classes. I successfully (at least without any warnings) compiled my file by calling: javac -cp relative_path_to_needed_classes relative_path_to_file_java\file.java Now if I want to run the result of compilation (file.class) by calling: java -cp relative_path_to_needed_classes relative_path_to_file_java\file I get: Error: Could not find or load main class relative_path_to_file_java\file I was trying a lot of combination to modify the -cp (eg. by adding .\;relative_path_to_file;) but still the closest where I get is: Exception in thread "main" java.lang.NoClassDefFoundError : relative_path_to_file\file (wrong name: file) The file from (wrong name: file) is the name of the file and the name of the public class within the file. I was reading a lot on SO and other sources but could not figure out what is wrong. Btw. as a result of compilation some other classes were created: file$1.class file$name1.class file$name2.class (where name1 and name2 are names of private classes within file.java) My questions are: What is (the most) probably source of my error / what am I doing wrong? What is the purpose of file$1.class? What is the minimum I should specify in -cp? May encoding play any role? Do every java class have to reside in a package? (rather not directly related to my issue) Do order of paths specified in -cp play any role in runtime?

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• Who architected / designed C++'s IOStreams, and would it still be considered well-designed by today'

  - by stakx

  First off, it may seem that I'm asking for subjective opinions, but that's not what I'm after. I'd love to hear some well-grounded arguments on this topic. In the hope of getting some insight into how a modern streams / serialization framework ought to be designed, I recently got myself a copy of the book Standard C++ IOStreams and Locales by Angelika Langer and Klaus Kreft. I figured that if IOStreams wasn't well-designed, it wouldn't have made it into the C++ standard library in the first place. After having read various parts of this book, I am starting to have doubts if IOStreams can compare to e.g. the STL from an overall architectural point-of-view. Read e.g. this interview with Alexander Stepanov (the STL's "inventor") to learn about some design decisions that went into the STL. What surprises me in particular: It seems to be unknown who was responsible for IOStreams' overall design (I'd love to read some background information about this — does anyone know good resources?); Once you delve beneath the immediate surface of IOStreams, e.g. if you want to extend IOStreams with your own classes, you get to an interface with fairly cryptic and confusing member function names, e.g. getloc/imbue, uflow/underflow, snextc/sbumpc/sgetc/sgetn, pbase/pptr/epptr (and there's probably even worse examples). This makes it so much harder to understand the overall design and how the single parts co-operate. Even the book I mentioned above doesn't help that much (IMHO). Thus my question: If you had to judge by today's software engineering standards (if there actually is any general agreement on these), would C++'s IOStreams still be considered well-designed? (I wouldn't want to improve my software design skills from something that's generally considered outdated.)

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• python: help defining/installing simple script to setup machine-specific information

  - by Jason S

  (This is related to scons but I think most of the following should be fairly general to python) I would like to define a python file/library that I put in a Well-Known Place somewhere on my computer that I can use to define machine-specific paths, and was looking for help on how to do this well, since I'm a beginner to Python & really only use it for my scons work. scons uses a SConstruct file which can execute python code. What I would like to do is something like this: My SConstruct file would contain this at the beginning: defaultEnv = JJJJJ.getMachineSpecificPaths() or (do both of these syntaxes work?) import JJJJJ defaultEnv = getMachineSpecificPaths() I define a JJJJJ.py file somewhere installed in the python dir which contains the following def getMachineSpecificPaths(): ... does something here, I don't know what ... that reads a file machine-specific-paths.txt (maybe it has the code Ross Rogers mentioned in my other question) located in the same directory as JJJJJ.py containing the following: machine-specific-paths.txt TI_C28_ROOT C:/appl/ti/ccs/?4.1.1/ccsv4/tools/co?mpiler/c2000 JSDB c:/bin/jsdb/jsdb.exe PYTHON_PATH c:/appl/python/2.6.4 The thing is, I don't really know much about the conventions in Python about where you put system-wide libraries and files. This is probably really simple to get right but I don't know how.

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• Server side form validation and POST data

  - by tomcritchlow

  Hi, I have a user input form here: http://www.7bks.com/create (Google login required) When you first create a list you are asked to create a public username. Unfortuantely currently there is no constraint to make this unique. I'm working on the code to enforce unique usernames at the moment and would like to know the best way to do it. Tech details: appengine, python, webapp framework What I'm planning is something like this: first the /create form posts the data to /inputlist/ (this is the same as currently happens) /inputlist/ queries the datastore for the given username. If it already exists then redirect back to /create display the /create page with all the info previously but with an additional error message of "this username is already taken" My question is: Is this the best way of handling server side validation? What's the best way of storing the list details while I verify and modify the username? As I see it I have 3 options to store the list details but I'm not sure which is "best": Store the list details in the session cookie (I am using GAEsessions for cookies) Define a separate POST class for /create and post the list data back from /inputlist/ to the /create page (currently /create only has a GET class) Store the list in the datastore, even though the username is non-unique. Thank you very much for your help :) I'm pretty new to python and coding in general so if I've missed something obvious my apologies. Tom PS - I'm sure I can eventually figure it out but I can't find any documentation on POSTing data using the webapp appengine framework which I'd need in order to do solution 2 above :s maybe you could point me in the right direction for that too? Thanks! PPS - It's a little out of date now but you can see roughly how the /create and /inputlist/ code works at the moment here: 7bks.com Gist

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• Returning true or error message in Ruby

  - by seaneshbaugh

  I'm wondering if writing functions like this is considered good or bad form. def test(x) if x == 1 return true else return "Error: x is not equal to one." end end And then to use it we do something like this: result = test(1) if result != true puts result end result = test(2) if result != true puts result end Which just displays the error message for the second call to test. I'm considering doing this because in a rails project I'm working on inside my controller code I make calls to a model's instance methods and if something goes wrong I want the model to return the error message to the controller and the controller takes that error message and puts it in the flash and redirects. Kinda like this def create @item = Item.new(params[:item]) if [email protected]? result = @item.save_image(params[:attachment][:file]) if result != true flash[:notice] = result redirect_to(new_item_url) and return end #and so on... That way I'm not constructing the error messages in the controller, merely passing them along, because I really don't want the controller to be concerned with what the save_image method itself does just whether or not it worked. It makes sense to me, but I'm curious as to whether or not this is considered a good or bad way of writing methods. Keep in mind I'm asking this in the most general sense pertaining mostly to ruby, it just happens that I'm doing this in a rails project, the actual logic of the controller really isn't my concern.

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• Problem using Lazy<T> from within a generic abstract class

  - by James Black

  I have a generic class that all my DAO classes derive from, which is defined below. I also have a base class for all my entities, but that is not generic. The method GetIdOrSave is going to be a different type than how I defined SabaAbstractDAO, as I am trying to get the primary key to fulfill the foreign key relationships, so this function goes out to either get the primary key or save the entity and then get the primary key. The last code snippet has a solution on how it will work if I get rid of the generic part, so I think this can be solved by using variance, but I can't figure out how to write an interface that will compile. public abstract class SabaAbstractDAO<T> { ... public K GetIdOrSave<K>(K item, Lazy<SabaAbstractDAO<BaseModel>> lazyitemdao) where K : BaseModel { if (item != null && item.Id.IsNull()) { var itemdao = lazyitemdao.Value; item.Id = itemdao.retrieveID(item); if (item.Id.IsNull()) { return itemdao.SaveData(item); } } return item; } } I am getting this error, when I try to compile: Argument 2: cannot convert from 'System.Lazy<ORNL.HRD.LMS.Dao.SabaCourseDAO>' to 'System.Lazy<ORNL.HRD.LMS.Dao.SabaAbstractDAO<ORNL.HRD.LMS.Models.BaseModel>>' I am trying to call it this way: GetIdOrSave(input.OfferingTemplate, new Lazy<SabaCourseDAO>( () => { return new SabaCourseDAO() { Dao = Dao }; }) ); If I change the definition to this, it works. public K GetIdOrSave<K>(K item, Lazy<SabaCourseDAO> lazyitemdao) where K : BaseModel { So, how can I get this to compile using variance (if needed) and generics, so I can have a very general method that will only work with BaseModel and AbstractDAO<BaseModel>? I expect I should only need to make the change in the method and perhaps abstract class definition, the usage should be fine.

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