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• View Controller's viewDidLoad method finishing before applicationDidFinishLaunching

  - by mwt

  I'm creating a fairly complex iPhone app using Core Data. Up until now, things have been working fine. As the app has been getting more complex, however, a new problem has come up: the first view controller is finishing its viewDidLoad method before the AppDelegate gets even halfway through its applicationDidFinishLaunching method. The view controller is not the root, which is a tab bar controller. The VC in question is the one for the default selected tab on the tab bar. It's getting instantiated by IB. Nothing like this has occurred before in my experience, and it's throwing off the important initialization I'm doing in the AppDelegate (getting objects from Core Data and preparing them for use) . Furthermore, it's intermittent -- sometimes the delegate does finish first. Has anyone else noticed a difficulty like this? Any sample code that deals with such an issue? I suppose that the answer is to make the VC load the data that the AppDelegate is getting ready only when the AppDelegate sends a message that it's ready. I'm a bit concerned that this is adding something that will just end up biting me in the butt later on.

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• REST API Best practice: How to accept as input a list of parameter values

  - by whatupwilly

  Hi All, We are launching a new REST API and I wanted some community input on best practices around how we should have input parameters formatted: Right now, our API is very JSON-centric (only returns JSON). The debate of whether we want/need to return XML is a separate issue. As our API output is JSON centric, we have been going down a path where our inputs are a bit JSON centric and I've been thinking that may be convenient for some but weird in general. For example, to get a few product details where multiple products can be pulled at once we currently have: http://our.api.com/Product?id=["101404","7267261"] Should we simplify this as: http://our.api.com/Product?id=101404,7267261 Or is having JSON input handy? More of a pain? We may want to accept both styles but does that flexibility actually cause more confusion and head aches (maintainability, documentation, etc.)? A more complex case is when we want to offer more complex inputs. For example, if we want to allow multiple filters on search: http://our.api.com/Search?term=pumas&filters={"productType":["Clothing","Bags"],"color":["Black","Red"]} We don't necessarily want to put the filter types (e.g. productType and color) as request names like this: http://our.api.com/Search?term=pumas&productType=["Clothing","Bags"]&color=["Black","Red"] Because we wanted to group all filter input together. In the end, does this really matter? It may be likely that there are so many JSON utils out there that the input type just doesn't matter that much. I know our javascript clients making AJAX calls to the API may appreciate the JSON inputs to make their life easier. Thanks, Will

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• User roles - why not store in session?

  - by Phil

  I'm porting an ASP.NET application to MVC and need to store two items relating to an authenitcated user: a list of roles and a list of visible item IDs, to determine what the user can or cannot see. We've used WSE with a web service in the past and this made things unbelievably complex and impossible to debug properly. Now we're ditching the web service I was looking foward to drastically simplifying the solution simply to store these things in the session. A colleague suggested using the roles and membership providers but on looking into this I've found a number of problems: a) It suffers from similar but different problems to WSE in that it has to be used in a very constrained way maing it tricky even to write tests; b) The only caching option for the RolesProvider is based on cookies which we've rejected on security grounds; c) It introduces no end of complications and extra unwanted baggage; All we want to do, in a nutshell, is store two string variables in a user's session or something equivalent in a secure way and refer to them when we need to. What seems to be a ten minute job has so far taken several days of investigation and to compound the problem we have now discovered that session IDs can apparently be faked, see http://blogs.sans.org/appsecstreetfighter/2009/06/14/session-attacks-and-aspnet-part-1/ I'm left thinking there is no easy way to do this very simple job, but I find that impossible to believe. Could anyone: a) provide simple information on how to make ASP.NET MVC sessions secure as I always believed they were? b) suggest another simple way to store these two string variables for a logged in user's roles etc. without having to replace one complex nightmare with another as described above? Thank you.

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• window.onload seems to trigger before the DOM is loaded (JavaScript)

  - by Dr. Monkey

  I am having trouble with the window.onload and document.onload events. Everything I read tells me these will not trigger until the DOM is fully loaded with all its resources, it seems like this isn't happening for me: I tried the following simple page in Chrome 4.1.249.1036 (41514) and IE 8.0.7600.16385 with the same result: both displayed the message "It failed!", indicating that myParagraph is not loaded (and so the DOM seems incomplete). <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <script type="text/javascript"> window.onload = doThis(); // document.onload gives the same result function doThis() { if (document.getElementById("myParagraph")) { alert("It worked!"); } else { alert("It failed!"); } } </script> </head> <body> <p id="myParagraph">Nothing is here.</p> </body> </html> I am using more complex scripts than this, in an external .js file, but this illustrates the problem. I can get it working by having window.onload set a timer for half a second to run doThis(), but this seems like an inelegant solution, and doesn't answer the question of why window.onload doesn't seem to do what everyone says it does. Another solution would be to set a timer that will check if the DOM is loaded, and if not it will just call itself half a second later (so it will keep checking until the DOM is loaded), but this seems overly complex to me. Is there a more appropriate event to use?

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• Practical size limitations for RDBMS

  - by grenade

  I am working on a project that must store very large datasets and associated reference data. I have never come across a project that required tables quite this large. I have proved that at least one development environment cannot cope at the database tier with the processing required by the complex queries against views that the application layer generates (views with multiple inner and outer joins, grouping, summing and averaging against tables with 90 million rows). The RDBMS that I have tested against is DB2 on AIX. The dev environment that failed was loaded with 1/20th of the volume that will be processed in production. I am assured that the production hardware is superior to the dev and staging hardware but I just don't believe that it will cope with the sheer volume of data and complexity of queries. Before the dev environment failed, it was taking in excess of 5 minutes to return a small dataset (several hundred rows) that was produced by a complex query (many joins, lots of grouping, summing and averaging) against the large tables. My gut feeling is that the db architecture must change so that the aggregations currently provided by the views are performed as part of an off-peak batch process. Now for my question. I am assured by people who claim to have experience of this sort of thing (which I do not) that my fears are unfounded. Are they? Can a modern RDBMS (SQL Server 2008, Oracle, DB2) cope with the volume and complexity I have described (given an appropriate amount of hardware) or are we in the realm of technologies like Google's BigTable? I'm hoping for answers from folks who have actually had to work with this sort of volume at a non-theoretical level.

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• Simulating pass by reference for an array in Java

  - by Leif Andersen

  I was wondering, in java, is it possible to in anyway, simulate pass by reference for an array? Yes, I know the language doesn't support it, but is there anyway I can do it. Say, for example, I want to create a method that reverses the order of all the elements in an array. (I know that this code snippet isn't the best example, as there is a better algorithms to do this, but this is a good example of the type of thing I want to do for more complex problems). Currently, I need to make a class like this: public static void reverse(Object[] arr) { Object[] tmpArr = new Object[arr.length]; count = arr.length - 1; for(Object i : arr) tmpArr[count--] = i; // I would like to do arr = tmpArr, but that will only make the shallow // reference tmpArr, I would like to actually change the pointer they passed in // Not just the values in the array, so I have to do this: count = arr.length - 1; for(Object i : tmpArr) arr[count--] = i; return; } Yes, I know that I could just swap the values until I get to the middle, and it would be much more efficient, but for other, more complex purposes, is there anyway that I can manipulate the actual pointer? Again, thank you.

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• Simulating pass by reference for an array reference (i.e. a reference to a reference) in Java

  - by Leif Andersen

  I was wondering, in java, is it possible to in anyway, simulate pass by reference for an array? Yes, I know the language doesn't support it, but is there anyway I can do it. Say, for example, I want to create a method that reverses the order of all the elements in an array. (I know that this code snippet isn't the best example, as there is a better algorithms to do this, but this is a good example of the type of thing I want to do for more complex problems). Currently, I need to make a class like this: public static void reverse(Object[] arr) { Object[] tmpArr = new Object[arr.length]; count = arr.length - 1; for(Object i : arr) tmpArr[count--] = i; // I would like to do arr = tmpArr, but that will only make the shallow // reference tmpArr, I would like to actually change the pointer they passed in // Not just the values in the array, so I have to do this: count = arr.length - 1; for(Object i : tmpArr) arr[count--] = i; return; } Yes, I know that I could just swap the values until I get to the middle, and it would be much more efficient, but for other, more complex purposes, is there anyway that I can manipulate the actual pointer? Again, thank you.

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• Append a dynamically changing watermark to a PDF in SharePoint

  - by ccomet

  This is primarily a question of possibilities more than instructions. I'm a programming consultant working on a WSS project site system for my client. We have a document library in which files are uploaded to go through a complex approval process. With multiple stages in this process, we have an extra field which dictates what the current status of the document is. Now, my client has become enamored with the idea of PDF watermarking. He wants the document (which is already a PDF) to be affixed with a watermark corresponding to the current status, such that with each stage of the approval process the watermark will change. One method, the traditional method for PDF watermarking, of accomplishing this is to have one "clean" copy of the document somewhere hidden on the site, and create a new PDF from it that has the watermark at each stage of the approval process. Since the filename will never change, this new PDF can be uploaded continually to a public library, always overwriting the old version and simulating a "dynamically changing watermark". However, in the various stages there will also be people uploading clean copies with corrections and suggestions, nevermind the complex nature of juggling around two libraries and the fact we double the number of files stored. My client and I agree that this is not a practical path to choose. What we would like to do is be able to "modify" the watermark in a PDF, so that we only have to keep one copy of the file. Unfortunately, from what I've seen, in most cases when you make something like a watermark, which in its nature is supposed to be "unmodifyable", you won't be able to edit it later. So, is it possible to have a part of a PDF which cannot be changed by anyone who downloads the file, but can be changed as part of a workflow or other object model process? Thanks in advance!

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• Model relationships in ASP.NET MVC

  - by Fabiano

  Hi I recently started evaluating ASP.NET MVC. While it is really easy and quick to create Controllers and Views for Models with only primitive properties (like shown in the starter videos from the official page) I didn't find any good way to work with references to complex types. Let's say, I have these Models: public class Customer { public int Id { get; set; } public string Name { get; set; } public Address Address { get; set; } public IList<Order> Orders { get; set; } } public class Address { public int Id { get; set; } public string ..... ..... } public class Order { public int Id { get; set; } public Customer Customer { get; set; } public string OrderName { get; set; } ..... } Note that I don't have foreign keys in the models (like it's typical for LINQ to SQL, which is also used in the sample video) but an object reference. How can I handle such references in asp.net mvc? Does someone has some good tips or links to tutorials about this problem? maybe including autobinding with complex types.

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• Which technology is best suited to store and query a huge readonly graph?

  - by asmaier

  I have a huge directed graph: It consists of 1.6 million nodes and 30 million edges. I want the users to be able to find all the shortest connections (including incoming and outgoing edges) between two nodes of the graph (via a web interface). At the moment I have stored the graph in a PostgreSQL database. But that solution is not very efficient and elegant, I basically need to store all the edges of the graph twice (see my question PostgreSQL: How to optimize my database for storing and querying a huge graph). It was suggested to me to use a GraphDB like neo4j or AllegroGraph. However the free version of AllegroGraph is limited to 50 million nodes and also has a very high-level API (RDF), which seems too powerful and complex for my problem. Neo4j on the other hand has only a very low level API (and the python interface is not mature yet). Both of them seem to be more suited for problems, where nodes and edges are frequently added or removed to a graph. For a simple search on a graph, these GraphDBs seem to be too complex. One idea I had would be to "misuse" a search engine like Lucene for the job, since I'm basically only searching connections in a graph. Another idea would be, to have a server process, storing the whole graph (500MB to 1GB) in memory. The clients could then query the server process and could transverse the graph very quickly, since the graph is stored in memory. Is there an easy possibility to write such a server (preferably in Python) using some existing framework? Which technology would you use to store and query such a huge readonly graph?

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• What is the correct way to implement a massive hierarchical, geographical search for news?

  - by Philip Brocoum

  The company I work for is in the business of sending press releases. We want to make it possible for interested parties to search for press releases based on a number of criteria, the most important being location. For example, someone might search for all news sent to New York City, Massachusetts, or ZIP code 89134, sent from a governmental institution, under the topic of "traffic". Or whatever. The problem is, we've sent, literally, hundreds of thousands of press releases. Searching is slow and complex. For example, a press release sent to Queens, NY should show up in the search I mentioned above even though it wasn't specifically sent to New York City, because Queens is a subset of New York City. We may also want to implement "and" and "or" and negation and text search to the query to create complex searches. These searches also have to be fast enough to function as dynamic RSS feeds. I really don't know anything about search theory, or how it's properly done. The way we are getting by right now is using a data mart to store the locations the releases were sent to in a single table. However, because of the subset thing mentioned above, the data mart is gigantic with millions of rows. And we haven't even implemented cities yet, and there are about 50,000 cities in the United States, which will exponentially increase the size of the data mart by so much I'm afraid it just won't work anymore. Anyway, I realize this is not a simple question and there won't be a "do this" answer. However, I'm hoping one of you can point me in the right direction where I can learn about how massive searches are done? Because I really know nothing about it. And such a search engine is turning out to be incredibly difficult to make. Thanks! I know there must be a way because if Google can search the entire internet we must be able to search our own database :-)

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• NSPredicate as a constraint solver?

  - by Felixyz

  I'm working on a project which includes some slightly more complex dynamic layout of interface elements than what I'm used to. I always feel stupid writing complex code that checks if so-and-so is close to such-and-such and in that case move it x% in some direction, etc. That's just not how programming should be done. Programming should be as declarative as possible! Precisely because what I'm going to do is fairly simple, I thought it would be a good opportunity to try something new, and I thought of using NSPredicate as a simple constraints solver. I've only used NSPredicate for very simple tasks so far, but I know that it capable of much more. Are there any ideas, experiences, examples, warnings, insights that could be useful here? I'll give a very simple example so there will be something concrete to answer. How could I use NSPredicate to solve the following constraints: viewB.xmid = (viewB.leftEdge + viewB.width) / 2 viewB.xmid = max(300, viewA.rightEdge + 20 + viewB.width/2) ("viewB should be horizontally centered on coordinate 300, unless its left edge gets within 20 pixels of viewB's right edge, in which case viewA's left edge should stay fixed at 20 pixels to the right of viewB's right edge and viewA's horizontal center get pushed to the right.") viewA.rightEdge and viewB.width can vary, and those are the 'input variables'. EDIT: Any solution would probably have to use the NSExpression method -(id)expressionValueWithObject:(id)object context:(NSMutableDictionary *)context. This answer is relevant.

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• Avoiding anemic domain model - a real example

  - by cbp

  I am trying to understand Anemic Domain Models and why they are supposedly an anti-pattern. Here is a real world example. I have an Employee class, which has a ton of properties - name, gender, username, etc public class Employee { public string Name { get; set; } public string Gender { get; set; } public string Username { get; set; } // Etc.. mostly getters and setters } Next we have a system that involves rotating incoming phone calls and website enquiries (known as 'leads') evenly amongst sales staff. This system is quite complex as it involves round-robining enquiries, checking for holidays, employee preferences etc. So this system is currently seperated out into a service: EmployeeLeadRotationService. public class EmployeeLeadRotationService : IEmployeeLeadRotationService { private IEmployeeRepository _employeeRepository; // ...plus lots of other injected repositories and services public void SelectEmployee(ILead lead) { // Etc. lots of complex logic } } Then on the backside of our website enquiry form we have code like this: public void SubmitForm() { var lead = CreateLeadFromFormInput(); var selectedEmployee = Kernel.Get<IEmployeeLeadRotationService>() .SelectEmployee(lead); Response.Write(employee.Name + " will handle your enquiry. Thanks."); } I don't really encounter many problems with this approach, but supposedly this is something that I should run screaming from because it is an Anemic Domain Model. But for me its not clear where the logic in the lead rotation service should go. Should it go in the lead? Should it go in the employee? What about all the injected repositories etc that the rotation service requires - how would they be injected into the employee, given that most of the time when dealing with an employee we don't need any of these repositories?

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• SQL with Regular Expressions vs Indexes with Logical Merging Functions

  - by geeko

  Hello Lads, I am trying to develop a complex textual search engine. I have thousands of textual pages from many books. I need to search pages that contain specified complex logical criterias. These criterias can contain virtually any compination of the following: A: Full words. B: Word roots (semilar to stems; i.e. all words with certain key letters). C: Word templates (in some languages are filled in certain templates to form various part of speech such as adjactives, past/present verbs...). D: Logical connectives: AND/OR/XOR/NOT/IF/IFF and parentheses to state priorities. Now, would it be faster to have the pages' full text in database (not indexed) and search though them all using SQL and Regular Expressions ? Or would it be better to construct indexes of word/root/template-page-location tuples. Hence, we can boost searching for individual words/roots/templates. However, it gets tricky as we interdouce logical connectives into our query. I thought of doing the following steps in such cases: 1: Seperately search for each individual words/roots/templates in the specified query. 2: On priority bases, we merge two result lists (from step 1) at a time depedning on the logical connective For example, if we are searching for "he AND (is OR was)": 1: We shall search for "he", "is" and "was" seperately and get result lists for each word. 2: Merge the result lists of "is" and "was" using the merging function OR-MERGE 3: Merge the merged result list from the OR-MERGE function with the one of "he" using the merging function AND-MERGE The result of step 3 is then returned as the result of the specified query. What do you think gurues ? Which is faster ? Any better ideas ? Thank you all in advance.

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• Generic object to object mapping with parametrized constructor

  - by Rody van Sambeek

  I have a data access layer which returns an IDataRecord. I have a WCF service that serves DataContracts (dto's). These DataContracts are initiated by a parametrized constructor containing the IDataRecord as follows: [DataContract] public class DataContractItem { [DataMember] public int ID; [DataMember] public string Title; public DataContractItem(IDataRecord record) { this.ID = Convert.ToInt32(record["ID"]); this.Title = record["title"].ToString(); } } Unfortanately I can't change the DAL, so I'm obliged to work with the IDataRecord as input. But in generat this works very well. The mappings are pretty simple most of the time, sometimes they are a bit more complex, but no rocket science. However, now I'd like to be able to use generics to instantiate the different DataContracts to simplify the WCF service methods. I want to be able to do something like: public T DoSomething<T>(IDataRecord record) { ... return new T(record); } So I'd tried to following solutions: Use a generic typed interface with a constructor. doesn't work: ofcourse we can't define a constructor in an interface Use a static method to instantiate the DataContract and create a typed interface containing this static method. doesn't work: ofcourse we can't define a static method in an interface Use a generic typed interface containing the new() constraint doesn't work: new() constraint cannot contain a parameter (the IDataRecord) Using a factory object to perform the mapping based on the DataContract Type. does work, but: not very clean, because I now have a switch statement with all mappings in one file. I can't find a real clean solution for this. Can somebody shed a light on this for me? The project is too small for any complex mapping techniques and too large for a "switch-based" factory implementation.

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• Define a swig interface file for generation of wrapper to every type from some header file

  - by Dmitriy Matveev

  Hi! We're using some C library in our Java project. Several years ago some other developer which has retired few years ago (as always) has created all the wrappers for us. The wrappers were generated by the swig, but the interface file is lost now. The basic idea of library and the wrappers for it is following: There only one function which returns pointer to some complex object. And there are wrapper for that function. The complex object is a tree-like structure with dozens of node kinds and types (C structures) used to represent them. There are hundreds of wrappers for every field of every type and we're trying to use them all. The library was updated some time ago and now there are some new data we unaware of which yet, but would like to use. This data is contained in some of the objects indirectly contained or referenced from the object created by the function we call (Some new fields and types were added). I know that I shouldn't make any changes to the wrappers by hand and should rather modify the interface, but as I already wrote it's missing. For now I only want to generate wrappers some few types which are added/changed and them to our old wrappers, but later I want to start creation of interface file which will define "what and how should be wrapped". All the definitions necessary for us are defined in single header file. Is it possible to tell swig to generate wrappers for every type in this header? If so, how can I write such interface file?

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• .Net xsd.exe tool doesn't generate all types

  - by Mrchief

  For some reason, MS .Net (v3.5) tool - xsd.exe doesn't generate types when they are not used inside any element. e.g. XSD File (I threw in the complex element to avoid this warning - "Warning: cannot generate classes because no top-level elements with complex type were found."): <?xml version="1.0" encoding="utf-8"?> <xs:schema targetNamespace="http://tempuri.org/XMLSchema.xsd" elementFormDefault="qualified" xmlns="http://tempuri.org/XMLSchema.xsd" xmlns:mstns="http://tempuri.org/XMLSchema.xsd" xmlns:xs="http://www.w3.org/2001/XMLSchema" > <xs:simpleType name="EnumTest"> <xs:restriction base="xs:string"> <xs:enumeration value="item1" /> <xs:enumeration value="item2" /> <xs:enumeration value="item3" /> </xs:restriction> </xs:simpleType> <xs:complexType name="myComplexType"> <xs:attribute name="Name" use="required" type="xs:string"/> </xs:complexType> <xs:element name="myElem" type="myComplexType"></xs:element> </xs:schema> When i run this thru xsd.exe using xsd /c xsdfile.xsd I don't see EnumTest in the generated cs file. Note; Even though I don't use the enum here, but in my actual project, I have cases like this where we send enum's string value as output. How can I force the xsd tool to include these? Or should I switch to some other tool? I work in Visual Studio 2008.

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• Drupal Views api, add simple argument handler

  - by LanguaFlash

  Background: I have a complex search form that stores the query and it's hash in a cache. Once the cache is set, I redirect to something like /searchresults/e6c86fadc7e4b7a2d068932efc9cc358 where that big long string on the end is the md5 hash of my query. I need to make a new argument for views to know what the hash is good for. The reason for all this hastle is because my original search form is way to complex and has way to many arguments to consider putting them all into the path and expecting to do the filtering with the normal views arguments. Now for my question. I have been reading views 2 documentation but not figuring out how to accomplish this custom argument. It doesn't seem to me like this should be as hard as it seems to me like it must be. Leaving aside any knowledge of the veiws api, it would seem that all I need is a callback function that will take the argument from the path as it's only argument and return a list of node id's to filter to. Can anyone point me to a solution or give me some example code? Thanks for your help! You guys are great. PS. I am pretty sure that my design is the best I can come up with, lets don't get off my question and into cross checking my design logic if we can help it.

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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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• (x86) Assembler Optimization

  - by Pindatjuh

  I'm building a compiler/assembler/linker in Java for the x86-32 (IA32) processor targeting Windows. High-level concepts of a "language" (in essential a Java API for creating executables) are translated into opcodes, which then are wrapped and outputted to a file. The translation process has several phases, one is the translation between languages: the highest-level code is translated into the medium-level code which is then translated into the lowest-level code (probably more than 3 levels). My problem is the following; if I have higher-level code (X and Y) translated to lower-level code (x, y, U and V), then an example of such a translation is, in pseudo-code: x + U(f) // generated by X + V(f) + y // generated by Y (An easy example) where V is the opposite of U (compare with a stack push as U and a pop as V). This needs to be 'optimized' into: x + y (essentially removing the "useless" code) My idea was to use regular expressions. For the above case, it'll be a regular expression looking like this: x:(U(x)+V(x)):null, meaning for all x find U(x) followed by V(x) and replace by null. Imagine more complex regular expressions, for more complex optimizations. This should work on all levels. What do you suggest? What would be a good approach to optimize in these situations?

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• Automatic music rating based on listening habits

  - by marco92w

  I've created a Winamp-like music player in Delphi. Not so complex, of course. Just a simple one. But now I would like to add a more complex feature: Songs in the library should be automatically rated based on the user's listening habits. This means: The application should "understand" if the user likes a song or not. And not only whether he/she likes it but also how much. My approach so far (data which could be used): Simply measure how often a song was played per time. Start counting time when the song was added to the library so that recent songs don't have any disadvantage. Measure how long a song was played on average (minutes). Starting a song but directly change to another one should have a bad influence on the ranking since the user didn't seem to like the song. ... Could you please help me with this problem? I would just like to have some ideas. I don't need the implementation in Delphi.

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• Custom Detail in Linq-to-SQL Master-Detail DataGridViews

  - by Andres

  Hi, looking for a way to create Linq-to-SQL Master-Detail WinForms DataGridViews where the Detail part of the Linq query is a custom one. Can do fine this: DataClasses1DataContext db = new DataClasses1DataContext(".\\SQLExpress"); var myQuery = from o in db.Orders select o; dataGridView1.DataSource = new BindingSource() { DataSource = myQuery }; dataGridView2.DataSource = new BindingSource() { DataSource = dataGridView1.DataSource, DataMember = "OrderDetails" }; but I'd like to have the Detail part under my precise control, like var myQuery = from o in db.Orders join od in db.OrderDetails on o.ID equals od.OrderID into MyOwnSubQuery select o; and use it for the second grid: dataGridView2.DataSource = new BindingSource() { DataSource = dataGridView1.DataSource, DataMember = "MyOwnSubQuery" // not working... }; the real reason I want it is a bit more complex (I'd like to have the Detail part to be some not-pre-defined join actually), but I'm hoping the above conveyed the idea. Can I only have the Detail part as a plain sub-table coming out of the pre-defined relation or can I do more complex stuff with the Detail part? Does anyone else feel this is kind of limited (if the first example is the best we can do)? Thanks!

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• JSF how to temporary disable validators to save draft

  - by Swiety

  I have a pretty complex form with lots of inputs and validators. For the user it takes pretty long time (even over an hour) to complete that, so they would like to be able to save the draft data, even if it violates rules like mandatory fields being not typed in. I believe this problem is common to many web applications, but can't find any well recognised pattern how this should be implemented. Can you please advise how to achieve that? For now I can see the following options: use of immediate=true on "Save draft" button doesn't work, as the UI data would not be stored on the bean, so I wouldn't be able to access it. Technically I could find the data in UI component tree, but traversing that doesn't seem to be a good idea. remove all the fields validation from the page and validate the data programmaticaly in the action listener defined for the form. Again, not a good idea, form is really complex, there are plenty of fields so validation implemented this way would be very messy. implement my own validators, that would be controlled by some request attribute, which would be set for standard form submission (with full validation expected) and would be unset for "save as draft" submission (when validation should be skipped). Again, not a good solution, I would need to provide my own wrappers for all validators I am using. But as you see no one is really reasonable. Is there really no simple solution to the problem?

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• Django: Paginator + raw SQL query

  - by Silver Light

  Hello! I'm using Django Paginator everywhere on my website and even wrote a special template tag, to make it more convenient. But now I got to a state, where I need to make a complex custom raw SQL query, that without a LIMIT will return about 100K records. How can I use Django Pagintor with custom query? Simplified example of my problem: My model: class PersonManager(models.Manager): def complicated_list(self): from django.db import connection #Real query is much more complex cursor.execute("""SELECT * FROM `myapp_person`"""); result_list = [] for row in cursor.fetchall(): result_list.append(row[0]); return result_list class Person(models.Model): name = models.CharField(max_length=255); surname = models.CharField(max_length=255); age = models.IntegerField(); objects = PersonManager(); The way I use pagintation with Django ORM: all_objects = Person.objects.all(); paginator = Paginator(all_objects, 10); try: page = int(request.GET.get('page', '1')) except ValueError: page = 1 try: persons = paginator.page(page) except (EmptyPage, InvalidPage): persons = paginator.page(paginator.num_pages) This way, Django get very smart, and adds LIMIT to a query when executing it. But when I use custom manager: all_objects = Person.objects.complicated_list(); all data is selected, and only then python list is sliced, which is VERY slow. How can I make my custom manager behave similar like built in one?

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• SVN marking file production ready

  - by dan.codes

  I am kind of new to SVN, I haven't used it in detail basically just checking out trunk and committing then exporting and deploying. I am working on a big project now with several developers and we are looking for the best deployment process. The one thing we are hung up on is the best way to tag, branch and so on. We are used to CVS where all you have to do is commit a file and tag it as production ready and if not that code will not get deployed. I see that SVN handles tagging differently then CVS. I figure I am looking at this and making it overly complex. It seems the only way to work on a project and commit files without it being in the production code is to do it in a branch and then merge those changes when you are ready for it to be deployed. I am assuming you could also be working on other code that should be deployed so you would have to be switching between working copies, because otherwise you are working on a branch that isn't getting mixed in with the trunk or production branch? This process seems overly complex and I was wondering if anyone could give me what you think is the best process for managing this.

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