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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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• Can addition of an ActionListener be short? Can I add arguments to the actionPerformed?

  - by Roman

  I have a big table containing a button in each cell. These buttons are very similar and do almost the same. If I add an action listener to every button in this way: tmp.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { proposition = proposition + action; SwingUtilities.invokeLater(new Runnable() { public void run() { updatePropositionPanel(); } }); } }); Actually, every action listener differ from all others by the value of the action. proposition and updatePropositionPanel are a field and a method of the class. First i thought that I can make it shorter if I do not use inner classes. So, I decided to program a new ActionListener class. But than I realized that in this case "proposition" will not be visible to the instances of this class. Then I decided to add the actionPerformed method to the current class and do that: addActionListener(this). But than I realized that I do not know how give arguments to the actionPerformed method. So, how does it work. Can I add an action listener in a short and elegent way?

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• Parsing Strings ( .crt files )

  - by user1661521

  Base Knowledge : I have a .crt file ( certification authoritie file ) and he is composed of many fields but in one line that resumes this question i have this : Certificate: ...(alot of stuff before)... Subject: C=US, ST=Maryland, L=Pasadena, O=Brent Baccala, OU=FreeSoft, CN=www.freesoft.org/[email protected] Subject Public Key Info: ...(alot of stuff after) and i need to parse the file to populate a .csv file and i have that done the problem that i need help is, i need to get the field: CN=www.fresoft.org but when i get this kind of CN=...(Value instead of the ...) with alot of slashes i get a error in the parsing like the raw string is: CN=foo/bar/the/hell/emailAddress=blablabla and i need only: foo/bar/the/hell and for a moment i got that in the correct column but when i dont have the emailAddress something just fail in my parsing and i then get in my CN .csv column the information wrong instead of |CN| foo/bar/the/hell i get: |CN| OU=FreeSoft, foo/bar/the/hell. I have this code doing the CN parsing: #!/bin/bash subject_line=$(echo $cert | grep -o "Subject:.*Subject Public Key Info") cn=$(echo $subject_line | grep -o "CN=.*" ) if [ $(echo $cn | grep -c ".*email.*") -gt 0 ]; then end_cn=$(echo $cn | grep -b -o emailAddress) end_cn_idx=$(echo $end_cn | grep -o .*:) final_end_cn=${end_cn_idx:0:-1} common_name=${cn:3:$final_end_cn-4} echo $common_name else end_cn=$(echo $cn | grep -b -o "Subject Public Key Info") end_cn_idx=$(echo $end_cn | grep -o .*:) final_end_cn=${end_cn_idx:0:-1} common_name=${cn:3:$final_end_cn-5} echo $common_name fi

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• PHP strtotime() looks like it is expecting a Euro format

  - by Jason Rhodes

  I've been using PHP's strtotime() method to accept a date field on a form. I love how powerful it is, in how it will accept "Tomorrow", "Next Thursday", or (supposedly) any date representation and convert it to the Unix timestamp. It's been working great -- until yesterday. Someone entered "2-4-10" and instead of logging Feb 4th, 2010, it logged April 10, 2002! So it expected Y-M-D instead of M-D-Y. I thought maybe the problem was just using a 2-digit year, so we tried again with "2-4-2010". That logged April 2nd, 2010! At that point I just don't understand what strtotime() is doing. PHP.net says it expects a US English date format. Why then would it assume D-M-Y? Is there a way around this? Or do I have to stop using strtotime()? Note: I just now did a test. When you use slashes instead of hyphen/dashes, it works fine, even with 2/4/10. Why on earth does that matter? And if that's all it is, should I just run str_replace("-", "/", $input) on the form input before passing it to strtotime()?

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• What is the best database structure for this scenario?

  - by Ricketts

  I have a database that is holding real estate MLS (Multiple Listing Service) data. Currently, I have a single table that holds all the listing attributes (price, address, sqft, etc.). There are several different property types (residential, commercial, rental, income, land, etc.) and each property type share a majority of the attributes, but there are a few that are unique to that property type. My question is the shared attributes are in excess of 250 fields and this seems like too many fields to have in a single table. My thought is I could break them out into an EAV (Entity-Attribute-Value) format, but I've read many bad things about that and it would make running queries a real pain as any of the 250 fields could be searched on. If I were to go that route, I'd literally have to pull all the data out of the EAV table, grouped by listing id, merge it on the application side, then run my query against the in memory object collection. This also does not seem very efficient. I am looking for some ideas or recommendations on which way to proceed. Perhaps the 250+ field table is the only way to proceed. Just as a note, I'm using SQL Server 2012, .NET 4.5 w/ Entity Framework 5, C# and data is passed to asp.net web application via WCF service. Thanks in advance.

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• Combining properties made available via webservices profile service aspnet

  - by Adam

  I really wasn't sure what the title for my question could be, so sorry if it's a bit vague. I'm working on an application that uses client application services for authentication/profile management etc. In web.config for my website, I have the following profile properties like this: <properties> <add name="FirstName" type="string" defaultValue="" customProviderData="FirstName;nvarchar"/> ... Basic things like first name, last name etc. I'm exposing properties for my client app like this: <system.web.extensions> <scripting> <webServices> <authenticationService enabled="true" requireSSL="false"/> <profileService enabled="true" readAccessProperties="UserProfile" writeAccessProperties="UserProfile"/> <roleService enabled="true"/> </webServices> </scripting> </system.web.extensions> What I'm wondering is whether it's possible to bundle all the individual profile properties into a single object for client apps to utilize? I originally had all my profile data stored as members of a single class (UserProfile) but I broke it all out so that I could use the SqlTableProfileProvider to store each field as individual columns in relevant tables. I know I can create an class with members for each type, I'm just not sure if there's an easy way to create an object with all my property values (other than assigning values to this object whenever I assign to the the standalone properties). I don't think I'm explaining this very well, so I'll try an example. Say in my website profile I have FirstName and LastName as properties. For my client application profileService I want to have one ReadAccessProperty FullName. Is there some way to automatically create FullName from the existing FirstName and LastName properties without having to also have a seperate FullName property (and manually assign data to it whenever I assign data to FirstName and LastName)?

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• Querying a database using Cocoa.

  - by S1syphus

  Hello everybody. Before I start a disclaimer, I should add a little disclaimer, that I am relatively new to Cocoa development and C in general. However I do have a copy of 'Cocoa Programming for Mac OS X 3rd edition' by Aaron Hillegass, which I am working through and using as a base, if anybody has a copy I am using the 'AmaZone' example on page 346 as a template and base. I trying to develop a small client app that takes a search string then displays results from a database accordingly. The database will contain a: list of files, their location, description & creation date, so for the moment the field number and types will remain the same. After looking around on SO, I saw something like: NSURL *myURL = [NSURL URLWithString:@"http://www.myserver.com/results.php"]; NSArray *sqlResults = [[NSArray alloc] initWithContentsOfURL:myURL]; I've worked with php before, so my current thinking after seeing this is create a php script on the server that queries the database, and creates an XML output. And with the XML response, just parse it. Would this be ok? as is there any major pitfalls anybody can see, that I can't. I know there are some database bundles, I've had a look at BaseTen for Postgres, but being relatively new to this, didn't want to get in over my head. Or if anybody else has any other suggestions and ideas, they would be greatly appreciated.

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• How do I properly implement a property in F#?

  - by Greg D

  Consider my first attempt, a simple type in F# like the following: type Test() = inherit BaseImplementingNotifyPropertyChangedViaOnPropertyChanged() let mutable prop: string = null member this.Prop with public get() = prop and public set value = match value with | _ when value = prop -> () | _ -> let prop = value this.OnPropertyChanged("Prop") Now I test this via C# (this object is being exposed to a C# project, so apparent C# semantics are desirable): [TestMethod] public void TaskMaster_Test() { var target = new FTest(); string propName = null; target.PropertyChanged += (s, a) => propName = a.PropertyName; target.Prop = "newString"; Assert.AreEqual("Prop", propName); Assert.AreEqual("newString", target.Prop); return; } propName is properly assigned, my F# Setter is running, but the second assert is failing because the underlying value of prop isn't changed. This sort of makes sense to me, because if I remove mutable from the prop field, no error is generated (and one should be because I'm trying to mutate the value). I think I must be missing a fundamental concept. What's the correct way to rebind/mutate prop in the Test class so that I can pass my unit test?

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• C# reference collection for storing reference types

  - by ivo s

  I like to implement a collection (something like List<T>) which would hold all my objects that I have created in the entire life span of my application as if its an array of pointers in C++. The idea is that when my process starts I can use a central factory to create all objects and then periodically validate/invalidate their state. Basically I want to make sure that my process only deals with valid instances and I don't re-fetch information I already fetched from the database. So all my objects will basically be in one place - my collection. A cool thing I can do with this is avoid database calls to get data from the database if I already got it (even if I updated it after retrieval its still up-to-date if of course some other process didn't update it but that a different concern). I don't want to be calling new Customer("James Thomas"); again if I initted James Thomas already sometime in the past. Currently I will end up with multiple copies of the same object across the appdomain - some out of sync other in sync and even though I deal with this using timestamp field on the MSSQL server I'd like to keep only one copy per customer in my appdomain (if possible process would be better). I can't use regular collections like List or ArrayList for example because I cannot pass parameters by their real local reference to the their existing Add() methods where I'm creating them using ref so that's not to good I think. So how can this be implemented/can it be implemented at all ? A 'linked list' type of class with all methods working with ref & out params is what I'm thinking now but it may get ugly pretty quickly. Is there another way to implement such collection like RefList<T>.Add(ref T obj)? So bottom line is: I don't want re-create an object if I've already created it before during the entire application life unless I decide to re-create it explicitly (maybe its out-of-date or something so I have to fetch it again from the db). Is there alternatives maybe ?

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• jQuery validate and tabs

  - by ntan

  Hi i am using jQuery validate for my form validation. The form is inside tabs.When i get an error i add an icon to the tab that error exist to be visual by the user So far so good. My problem is that after correct the error i can not remove the error in tab icon. I was assuming that validator is accessible via success but its not Assuming that the first tab (tab0) has 3 field for validation (field1,field2,field3) Here is the full code $("form#Form1") .validate({ invalidHandler: function(form, validator) { //TAB 0 if (validator.errorMap.field1 != "" && validator.errorMap.field2 != "" && validator.errorMap.field3 != "") { if ($("#tabs>ul>li").eq(0).find("img").length == 0) { $("#tabs>ul>li").eq(0).prepend("<img src=\"error.gif\">"); } } }, errorClass: "errorField", errorElement: "p", errorPlacement: function(error, element) { var parent = element.parent(); parent.addClass("error"); error.prependTo( parent ); }, //validator in not accessible via success //so my code its not working success: function(element,validator) { var parent = element.parent(); parent.removeClass("error"); $(parent).children("p.errorField").remove(); //TAB 0 if (validator.errorMap.field1 == "" && validator.errorMap.field2 == "" && validator.errorMap.field2 == "") { if ($("#tabs>ul>li").eq(0).find("img").length == 0) { $("#tabs>ul>li").eq(0).find("img").remove(); } } }, rules: { field1: { required: true }, field2: { required: true }, field3: { required: true } } }); Any suggestion is welcome.

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• Setting nested object to null when selected option has empty value

  - by Javi

  Hello, I have a Class which models a User and another which models his country. Something like this: public class User{ private Country country; //other attributes and getter/setters } public class Country{ private Integer id; private String name; //other attributes and getter/setters } I have a Spring form where I have a combobox so the user can select his country or can select the undefined option to indicate he doen't want to provide this information. So I have something like this: <form:select path="country"> <form:option value="">-Select one-</form:option> <form:options items="${countries}" itemLabel="name" itemValue="id"/> </form:select> In my controller I get the autopopulated object with the user information and I want to have country set to null when the "-Select one-" option has been selected. So I have set a initBinder with a custom editor like this: @InitBinder protected void initBinder(WebDataBinder binder) throws ServletException { binder.registerCustomEditor(Country.class, "country", new CustomCountryEditor()); } and my editor do something like this: public class CustomCountryEditor(){ @Override public String getAsText() { //I return the Id of the country } @Override public void setAsText(String str) { //I search in the database for a country with id = new Integer(str) //and set country to that value //or I set country to null in case str == null } } When I submit the form it works because when I have country set to null when I have selected "-Select one-" option or the instance of the country selected. The problem is that when I load the form I have a method like the following one to load the user information. @ModelAttribute("user") public User getUser(){ //loads user from database } The object I get from getUser() has country set to a specific country (not a null value), but in the combobox is not selected any option. I've debugged the application and the CustomCountryEditor works good when setting and getting the text, thoughgetAsText method is called for every item in the list "countries" not only for the "country" field. Any idea? Is there a better way to set null the country object when I select no country option in the combobox? Thanks

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• Can the Singleton be replaced by Factory?

  - by lostiniceland

  Hello Everyone There are already quite some posts about the Singleton-Pattern around, but I would like to start another one on this topic since I would like to know if the Factory-Pattern would be the right approach to remove this "anti-pattern". In the past I used the singleton quite a lot, also did my fellow collegues since it is so easy to use. For example, the Eclipse IDE or better its workbench-model makes heavy usage of singletons as well. It was due to some posts about E4 (the next big Eclipse version) that made me start to rethink the singleton. The bottom line was that due to this singletons the dependecies in Eclipse 3.x are tightly coupled. Lets assume I want to get rid of all singletons completely and instead use factories. My thoughts were as follows: hide complexity less coupling I have control over how many instances are created (just store the reference I a private field of the factory) mock the factory for testing (with Dependency Injection) when it is behind an interface In some cases the factories can make more than one singleton obsolete (depending on business logic/component composition) Does this make sense? If not, please give good reasons for why you think so. An alternative solution is also appreciated. Thanks Marc

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• JSF/Facelets: set `action` attribute to a dynamically evaluated string

  - by harto

  In my JSF/Facelets application, I want to dynamically generate a breadcrumb trail from a list of page IDs using a custom tag: <foo:breadcrumbs trail="foo,bar,baz"/> This should generate something like: <h:commandLink action="foo" ... /> <h:commandLink action="bar" ... /> <!-- (etc.) --> My code looks something like this: <ui:repeat value="#{fn:split(trail, ',')}" var="key"> <h:commandLink action="#{key}" ... /> </ui:repeat> The problem with this code is that #{key} is interpreted as a method binding. However, I just want the string value of #{key} to be returned as the navigation outcome. How can I achieve this? The only thing I could think of was creating a dummy managed-bean that has an outcome field and an action handler, and invoke it like so: <h:commandLink action="#{dummy.click}" ...> <f:setPropertyActionListener target="#{dummy.outcome}" value="#{key}" /> </h:commandLink> with the dummy class defined like so: public class Dummy { private String outcome; public String click() { return outcome; } public void setOutcome(String outcome) { this.outcome = outcome; } public void getOutcome() { return outcome; } } That seems ugly though, and I don't know if it would work.

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• ASP.NET MVC: Returning a view with querystring in tact

  - by ajbeaven

  I'm creating a messaging web app in ASP.NET and are having some problems when displaying an error message to the user if they go to send a message and there is something wrong. A user can look through profiles of people and then click, 'send a message'. The following action is called (url is /message/create?to=username) and shows them a page where they can enter their message and send it: public ActionResult Create(string to) { ViewData["recipientUsername"] = to; return View(); } On the page that is displayed, the username is entered in to a hidden input field. When the user clicks 'send': [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(string message, string to) { try { //do message stuff that errors out } catch { ModelState.AddModelErrors(message.GetRuleViolations()); //adding errors to modelstate } return View(); } So now the error message is displayed to the user fine, however the url is changed in that it no longer has the querystring (/message/create). Again, this would be fine except that when the user clicks the refresh button, the page errors out as the Create action no longer has the 'to' parameter. So I'm guessing that I need to maintain my querystring somehow. Is there any way to do this or do I need to use a different method altogether?

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• For the professional programmers - do you still write code for fun at home ? [closed]

  - by Led

  Possible Duplicate: Do you ever code just for fun? I've been working as a 'professional' coder for about 11 years. (I've just turned 33.) When I talk to my collegues, I find that most of them actually don't program any more in their spare time - 8 (or 10 :)) hours a day at their job is enough for them. A difference between me and them might be that I was always programming for fun (demoscene stuff etc.) which is why I got into the field, while most of them picked up programming later on (at university or whatever). When I get home my head is always full of ideas, so usually I have a hobby-project going on. Is it weird to spend 8 hours a day programming, and then get home, have dinner, and do some more ? For me the reasons are just - ideas : trying stuff - wanting to develop something all by myself, so when it's finished I can claim it as my own victory How about you ? And if you do, do you have other reasons to do so ? Edit: And if you've got sparetime projects, it might be fun to tell us a bit about it :) Spamming a link to your site/hobbyproject won't be frowned upon here ! Edit2: Vote for this if you want to encourage companies to make monitors that'll give you a nice tan ! ;-)

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• Modify static variables while debugging in Eclipse

  - by sleske

  As an extension the the question "Modify/view static variables while debugging in Eclipse", I'd like to be able to modify static variables while debugging in Eclipse. For instance and local variables, I can just choose the variable in the "Variables" view of Eclipse, and use the context menu "Change value..." to change the value. This is not possible for arbitrary static variables, because they do not appear in the "Variables" view. What I tried: If you choose "Java / Show static variables" from the triangle menu in the "Variables" view, you can see and modify static member variables of the variables listed in the "Variables view". However, I did not find how to access a static member of a class whose instance does not appear in the "Variables view". You can of course enter a static member as an expression into the "Expression view" (using fully qualified name). Then you can see the value, but the "Expression view" does not have an option to modify the value (it does allow to modify members of an expression, but not the expression itself, even if the expression is a field). So, if I have a static variable like a boolean MyClass.disableAllBugs, is there a way to change MyClass.disableAllBugs during debugging? As an aside: I realize that even having public mutable static fields (i.e. mutable global variables) is very bad style. But some codebases have it, and then it's sometimes useful to modify it while debugging.

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• Rails - handling global site settings

  - by egarcia

  I'm developing a new rails application which is supposed to be installed several times in order to implement several sites. There are some things, like the "Site Title" or the "Default Number of Items per Page" that clearly belong to a "global settings" table / config file. I've made a list of the things I think I'll need: ActiveRecord model that is capable of: Storing different kinds of data. I suppose this would be accomplished encoding the values on a string on the db, probably with a "type" field. Indexing settings by name Validations based on a "type" attribute (i.e. don't accept invalid dates on "date" settings) Validations based on a allows_nil property. A controller that allows me to change settings via views. I'm pretty sure I could implement this myself, but I'm not willing to reinvent the wheel. I've done some searching, but I could only find rails-settings, which doesn't really serve me: I need a proper model & controller so I can use declarative-authorization, and it does not provide any controller or view facilities. Is there a gem or plugin out there that implements what I want, or any library I should look at? Thanks a lot.

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• Can't get this SPARQL query to work

  - by Jason

  Okay, I'm just learning to use SPARQL to query data from dbpedia.org and I'm using dbpedia's http://dbpedia.org/snorql/ to run my queries in. I am trying to get a list of MusicalArtists based on searching for the same string over three fields like so: SELECT ?subject ?artistRdfsLabel ?artistFoafName ?artistDbpedia2Name WHERE { ?subject rdf:type <http://dbpedia.org/ontology/MusicalArtist> . OPTIONAL { ?subject rdfs:label ?artistRdfsLabel . } OPTIONAL { ?subject foaf:name ?artistFoafName . } OPTIONAL { ?subject dbpedia2:name ?artistDbpedia2Name . } FILTER ( str(?artistRdfsLabel) = "Stevie Nicks" || str(?artistFoafName) = "Stevie Nicks" || str(?artistDbpedia2Name) = "Stevie Nicks" ) } LIMIT 10 This works because "Stevie Nicks" has all three fields (rdfs:label, foaf:name, dbpedia2:name). But when I try to query by another MusicalArtist that doesn't have all three ("Depeche Mode" for example) I get no results. I have tried various things like BIND(COALESCE(?field,...,...) AS ?artistName) to filter by ?artistName and I also tried UNION but nothing seems to work. Can someone point out the error of my SPARQL ways? :) Thanks! Jason

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• I have two choices of Master's classes this fall. Which is the most useful?

  - by ahplummer

  (For background purposes and context): I am a Software Engineer, and manage other Software Engineers currently. I kind of wear two hats right now: one of a programmer, and one as a 'team lead'. In this regard, I've started going back to school to get my Master's degree with an emphasis in Computer Science. I already have a Bachelor's in Computer Science, and have been working in the field for about 13 years. Our primary development environment is a Windows environment, writing in .NET, Delphi, and SQL Server. Choice #1: CST 798 DATA VISUALIZATION Course Description: Basically, this is a course on the "Processing" language: http://processing.org/ Choice #2: CST 711 INFORMATICS Course Description: (From catalog): Informatics is the science of the use and processing of data, information, and knowledge. This course covers a variety of applied issues from information technology, information management at a variety of levels, ranging from simple data entry, to the creation, design and implementation of new information systems, to the development of models. Topics include basic information representation, processing, searching, and organization, evaluation and analysis of information, Internet-based information access tools, ethics and economics of information sharing.

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• Algorithm possible amounts (over)paid for a specific price, based on denominations

  - by Wrikken

  In a current project, people can order goods delivered to their door and choose 'pay on delivery' as a payment option. To make sure the delivery guy has enough change customers are asked to input the amount they will pay (e.g. delivery is 48,13, they will pay with 60,- (3*20,-)). Now, if it were up to me I'd make it a free field, but apparantly higher-ups have decided is should be a selection based on available denominations, without giving amounts that would result in a set of denominations which could be smaller. Example: denominations = [1,2,5,10,20,50] price = 78.12 possibilities: 79 (multitude of options), 80 (e.g. 4*20) 90 (e.g. 50+2*20) 100 (2*50) It's international, so the denominations could change, and the algorithm should be based on that list. The closest I have come which seems to work is this: for all denominations in reversed order (large=>small) add ceil(price/denomination) * denomination to possibles baseprice = floor(price/denomination) * denomination; for all smaller denominations as subdenomination in reversed order add baseprice + (ceil((price - baseprice) / subdenomination) * subdenomination) to possibles end for end for remove doubles sort Is seems to work, but this has emerged after wildly trying all kinds of compact algorithms, and I cannot defend why it works, which could lead to some edge-case / new countries getting wrong options, and it does generate some serious amounts of doubles. As this is probably not a new problem, and Google et al. could not provide me with an answer save for loads of pages calculating how to make exact change, I thought I'd ask SO: have you solved this problem before? Which algorithm? Any proof it will always work?

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• Random Pairings that don't Repeat

  - by Andrew Robinson

  This little project / problem came out of left field for me. Hoping someone can help me here. I have some rough ideas but I am sure (or at least I hope) a simple, fairly efficient solution exists. Thanks in advance.... pseudo code is fine. I generally work in .NET / C# if that sheds any light on your solution. Given: A pool of n individuals that will be meeting on a regular basis. I need to form pairs that have not previously meet. The pool of individuals will slowly change over time. For the purposes of pairing, (A & B) and (B & A) constitute the same pair. The history of previous pairings is maintained. For the purpose of the problem, assume an even number of individuals. For each meeting (collection of pairs) and individual will only pair up once. Is there an algorithm that will allow us to form these pairs? Ideally something better than just ordering the pairs in a random order, generating pairings and then checking against the history of previous pairings. In general, randomness within the pairing is ok.

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• General many-to-many relationship problem ( Postgresql )

  - by David

  Hi, i have two tables: CREATE TABLE "public"."auctions" ( "id" VARCHAR(255) NOT NULL, "auction_value_key" VARCHAR(255) NOT NULL, "ctime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, "mtime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, CONSTRAINT "pk_XXXX2" PRIMARY KEY("id"), ); and CREATE TABLE "public"."auction_values" ( "id" NUMERIC DEFAULT nextval('default_seq'::regclass) NOT NULL, "fk_auction_value_key" VARCHAR(255) NOT NULL, "key" VARCHAR(255) NOT NULL, "value" TEXT, "ctime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, "mtime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, CONSTRAINT "pk_XXXX1" PRIMARY KEY("id"), ); if i want to create a many-to-many relationship on the auction_value_key like this: ALTER TABLE "public"."auction_values" ADD CONSTRAINT "auction_values_fk" FOREIGN KEY ("fk_auction_value_key") REFERENCES "public"."auctions"("auction_value_key") ON DELETE NO ACTION ON UPDATE NO ACTION NOT DEFERRABLE; i get this SQL error: ERROR: there is no unique constraint matching given keys for referenced table "auctions" Question: As you might see, i want "auction_values" to be be "reused" by different auctions without duplicating them for every auction... So i don't want a key relation on the "id" field in the auctions table... Am i thinking wrong here or what is the deal? ;) Thanks

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• Really simple JSON serialization in .NET

  - by Evgeny

  I have some simple .NET objects I'd like to serialize to JSON and back again. The set of objects to be serialized is quite small and I control the implementation, so I don't need a generic solution that will work for everything. Since my assembly will be distributed as a library I'd really like to avoid a dependency on some third-party DLL: I just want to give users one assembly that they can reference. I've read the other questions I could find on converting to and from JSON in .NET. The recommended solution of JSON.NET does work, of course, but it requires distributing an extra DLL. I don't need any of the fancy features of JSON.NET. I just need to handle a simple object (or even dictionary) that contains strings, integers, DateTimes and arrays of strings and bytes. On deserializing I'm happy to get back a dictionary - it doesn't need to create the object again. Is there some really simple code out there that I could compile into my assembly to do this simple job? I've also tried System.Web.Script.Serialization.JavaScriptSerializer, but where it falls down is the byte array: I want to base64-encode it and even registering a converter doesn't let me easily accomplish that due to the way that API works (it doesn't pass in the name of the field).

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• random data using php & mysql

  - by Prakash

  I have mysql database structure like below: CREATE TABLE test ( id int(11) NOT NULL auto_increment, title text NULL, tags text NULL, PRIMARY KEY (id) ); data on field tags is stored as a comma separated text like html,php,mysql,website,html etc... now I need create an array that contains around 50 randomly selected tags from random records. currently I am using rand() to select 15 random mysql data from database and then holding all the tags from 15 records in an array. Then I am using array_rand() for randomizing the array and selecting only 50 random records. $query=mysql_query("select * from test order by id asc, RAND() limit 15"); $tags=""; while ($eachData=mysql_fetch_array($query)) { $additionalTags=$eachData['tags']; if ($tags=="") { $tags.=$additionalTags; } else { $tags.=$tags.",".$additionalTags; } } $tags=explode(",", $tags); $newTags=array(); foreach ($tags as $tag) { $tag=trim($tag); if ($tag!="") { if (!in_array($tag, $newTags)) { $newTags[]=$tag; } } } $random_newTags=array_rand($newTags, 50); Now I have huge records on the database, and because of that; rand() is performing very slow and sometimes it doesn't work. So can anyone let me know how to handle this situation correctly so that my page will work normally.

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• How can I get bitfields to arrange my bits in the right order?

  - by Jim Hunziker

  To begin with, the application in question is always going to be on the same processor, and the compiler is always gcc, so I'm not concerned about bitfields not being portable. gcc lays out bitfields such that the first listed field corresponds to least significant bit of a byte. So the following structure, with a=0, b=1, c=1, d=1, you get a byte of value e0. struct Bits { unsigned int a:5; unsigned int b:1; unsigned int c:1; unsigned int d:1; } __attribute__((__packed__)); (Actually, this is C++, so I'm talking about g++.) Now let's say I'd like a to be a six bit integer. Now, I can see why this won't work, but I coded the following structure: struct Bits2 { unsigned int a:6; unsigned int b:1; unsigned int c:1; unsigned int d:1; } __attribute__((__packed__)); Setting b, c, and d to 1, and a to 0 results in the following two bytes: c0 01 This isn't what I wanted. I was hoping to see this: e0 00 Is there any way to specify a structure that has three bits in the most significant bits of the first byte and six bits spanning the five least significant bits of the first byte and the most significant bit of the second? Please be aware that I have no control over where these bits are supposed to be laid out: it's a layout of bits that are defined by someone else's interface.

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