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• Is there a recommended way to communicate scientific/engineering programming to C developers?

  - by ggkmath

  Hi, I have a lot of MATLAB code that needs to get ported to C (execution speed is critical for this work) as part of a back-end process for a web application. When I attempt to outsource this code to a C developer, I assume (correct me if I'm wrong) few C developers also understand MATLAB code (things like indexing and memory management are different, etc.). I wonder if there are any C developers out there that can recommend a procedure for me to follow to best communicate what the code does? For example, should I provide the MATLAB code and explain what it's doing line by line? Or, should I just provide the math/algorithm, explain it in plain English, and let the C developer implement it with this understanding in his/her own way (e.g. can I assume the developer understands how to work with complex math (i.e. imaginary numbers), how to generate histograms, perform an FFT, etc.)? Or, is there a better method? I expect I'm not the first to need to do this, so I wonder if any C developers out there ran into this situation and can share any conventional wisdom how they'd like this task to be transferred? Thanks in advance for any comments.

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• Ruby integer to string key

  - by Gene

  A system I'm building needs to convert non-negative Ruby integers into shortest-possible UTF-8 string values. The only requirement on the strings is that their lexicographic order be identical to the natural order on integers. What's the best Ruby way to do this? We can assume the integers are 32 bits and the sign bit is 0. This is successful: (i >> 24).chr + ((i >> 16) & 0xff).chr + ((i >> 8) & 0xff).chr + (i & 0xff).chr But it appears to be 1) garbage-intense and 2) ugly. I've also looked at pack solutions, but these don't seem portable due to byte order. FWIW, the application is Redis hash field names. Building keys may be a performance bottleneck, but probably not. This question is mostly about the "Ruby way".

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• Cross-browser method for getting width and height of a DIV?

  - by thinkthank

  This is my first post, so please go easy on me. I'm sure I'm doing everything wrong. However, I couldn't find any posts that answered the question above. I use jQuery. I'm trying to find a way to get the current width and height of a DIV element, even if they're set to "auto". I've found many ways to do this, but no method returns the same width in IE. It is important that this method is cross-browser, as it will break the layout of the page if different numbers are returned in different browsers. .width() and .height() do not work because in IE, padding is subtracted (e.g. width() returns 25 where width is 30 and padding is 5). .outerWidth() and .outerHeight() are not consistent either. While they work IE (believe it or not) in FF, the padding is added again to the full width (e.g. outerWidth() returns 110 in FF where width is 100px and padding is 10px). Is there any way out of this mess without writing complex browser checks? Thanks!

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• Do I need to Salt and Hash a randomly generated token?

  - by wag2639

  I'm using Adam Griffiths's Authentication Library for CodeIgniter and I'm tweaking the usermodel. I came across a generate function that he uses to generate tokens. His preferred approach is to reference a value from random.org but I considered that superfluous. I'm using his fall back approach of randomly generating a 20 character long string: $length = 20; $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; $token = ''; for ($i = 0; $i < $length; $i++) { $token .= $characters[mt_rand(0, strlen($characters)-1)]; } He then hashes this token using a salt (I'm combing code from different functions) sha1($this->CI->config->item('encryption_key').$str); I was wondering if theres any reason to to run the token through the salted hash? I've read that simply randomly generating strings was a naive way of making random passwords but is the sh1 hash and salt necessary? Note: I got my encryption_key from https://www.grc.com/passwords.htm (63 random alpha-numeric)

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• WCF - "Encountered unexpected character 'c'."

  - by Villager

  Hello, I am trying to do something that I thought would be simple. I need to create a WCF service that I can post to via JQuery. I have an operation in my WCF service that is defined as follows: [OperationContract] [WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.WrappedRequest, RequestFormat=WebMessageFormat.Json, ResponseFormat=WebMessageFormat.Json)] public string SendMessage(string message, int urgency) { try { // Do stuff return "1"; // 1 represents success } catch (Exception) { return "0"; } } I then try to access this operation from an ASP.NET page via JQuery. My JQuery code to access this operation looks like the following: function sendMessage(message) { $.ajax({ url: "/resources/services/myService.svc/SendMessage", type: "POST", contentType: "application/json; charset=utf-8", data: ({ message: message, urgency: '1' }), dataType: "json", success: function (data) { alert("here!"); }, error: function (req, msg, obj) { alert("error: " + req.responseText); } }); } When I execute this script, the error handler is tripped. In it, I receive an error that says: "Encountered unexpected character 'c'." This message is included with a long stack trace. My question is, what am I doing wrong? I have received other posts such as this one (http://stackoverflow.com/questions/320291/how-to-post-an-array-of-complex-objects-with-json-jquery-to-asp-net-mvc-controll) without any luck. How do I get this basic interaction working? Thank you!

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• Need Help finding an appropriate task assignment algorithm for a college project involving coordinat

  - by Trif Mircea

  I am a long time lurker here and have found over time many answers regarding jquery and web development topics so I decided to ask a question of my own. This time I have to create a c++ project for college which should help manage the workflow of a company providing all kinds of services through in the field teams. The ideas I have so far are: client-server application; the server is a dispatcher where all the orders from clients get and the clients are mobile devices (PDAs) each team in the field having one a order from a client is a task. Each task is made up of a series of subtasks. You have a database with estimations on how long a task should take to complete you also know what tasks or subtasks each team on the field can perform based on what kind of specialists made up the team (not going to complicate the problem by adding needed materials, it is considered that if a member of a team can perform a subtask he has the stuff needed) Now knowing these factors, what would a good task assignment algorithm be? The criteria is: how many tasks can a team do, how many tasks they have in the queue, it could also be location, how far away are they from the place but I don't think I can implement that.. It needs to be efficient and also to adapt quickly is the human dispatcher manually assigns a task. Any help or leads would be really appreciated. Also I'm not 100% sure in the idea so if you have another way you would go about creating such an application please share, even if it just a quick outline. I have to write a theoretical part too so even if the ideas are far more complex that what i outlined that would be ok ; I'd write those and implement what I can. Edit: C++ is the only language I know unfortunately.

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• How to get the text content on the swt table with arbitrary controls

  - by amarnath vishwakarma

  I have different controls placed on a table using TableEditor. ... TableItem [] items = table.getItems (); for (int i=0; i<items.length; i++) { TableEditor editor = new TableEditor (table); final Text text1 = new Text (table, SWT.NONE); text1.setText(listSimOnlyComponents.get(i).getName()); text1.setEditable(false); editor.grabHorizontal = true; editor.setEditor(text1, items[i], 0); editor = new TableEditor (table); final CCombo combo1 = new CCombo (table, SWT.NONE); combo1.setText(""); Set<String> comps = mapComponentToPort.keySet(); for(String comp:comps) combo1.add(comp); editor.grabHorizontal = true; editor.setEditor(combo1, items[i], 1); } //end of for ... When I try to get the text on the table using getItem(i).getText, I get empty string ... TableItem [] items = table.getItems (); for(int i=0; i<items.length; i++) { TableItem item = items[i]; String col0text = items[i].getText(0); //this text is empty String col1text = items[i].getText(1); //this text is empty } ... Why does getText returns empty strings even when I have text appearing on the table?

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• Short snippet summarizing a webpage?

  - by Legend

  Is there a clean way of grabbing the first few lines of a given link that summarizes that link? I have seen this being done in some online bookmarking applications but have no clue on how they were implemented. For instance, if I give this link, I should be able to get a summary which is roughly like: I'll admit it, I was intimidated by MapReduce. I'd tried to read explanations of it, but even the wonderful Joel Spolsky left me scratching my head. So I plowed ahead trying to build decent pipelines to process massive amounts of data Nothing complex at first sight but grabbing these is the challenging part. Just the first few lines of the actual post should be fine. Should I just use a raw approach of grabbing the entire html and parsing the meta tags or something fancy like that (which obviously and unfortunately is not generalizable to every link out there) or is there a smarter way to achieve this? Any suggestions? Update: I just found InstaPaper do this but am not sure if it is getting the information from RSS feeds or some other way.

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• Move SELECT to SQL Server side

  - by noober

  Hello all, I have an SQLCLR trigger. It contains a large and messy SELECT inside, with parts like: (CASE WHEN EXISTS(SELECT * FROM INSERTED I WHERE I.ID = R.ID) THEN '1' ELSE '0' END) AS IsUpdated -- Is selected row just added? as well as JOINs etc. I like to have the result as a single table with all included. Question 1. Can I move this SELECT to SQL Server side? If yes, how to do this? Saying "move", I mean to create a stored procedure or something else that can be executed before reading dataset in while cycle. The 2 following questions make sense only if answer is "yes". Why do I want to move SELECT? First off, I don't like mixing SQL with C# code. At second, I suppose that server-side queries run faster, since the server have more chances to cache them. Question 2. Am I right? Is it some sort of optimizing? Also, the SELECT contains constant strings, but they are localizable. For instance, WHERE R.Status = "Enabled" "Enabled" should be changed for French, German etc. So, I want to write 2 static methods -- OnCreate and OnDestroy -- then mark them as stored procedures. When registering/unregistering my assembly on server side, just call them respectively. In OnCreate format the SELECT string, replacing {0}, {1}... with required values from the assembly resources. Then I can localize resources only, not every script. Question 3. Is it good idea? Is there an existing attribute to mark methods to be executed by SQL Server automatically after (un)registartion an assembly? Regards,

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• ResXResourceWriter Chops off end of file

  - by Aaron Salazar

  I'm trying to create a .resx file from a dictionary of strings. Luckily the .Net framework has a ResXResourceWriter class. The only problem is that when I create the file using the code below, the last few lines of my generated resx file are missing. I checked my Dictionary and it contains all the string pairs that I expect. public void ExportToResx(Dictionary<string,string> resourceDictionary, string fileName) { var writer = new ResXResourceWriter(fileName); foreach (var resource in resourceDictionary) { writer.AddResource(resource.Key, resource.Value); } } Unfortunately, it is a little difficult to show the entire resx file since it has 2198 (should have 2222) lines but here is the last little bit: ... 2195 <data name="LangAlign_ReportIssue" xml:space="preserve"> 2196 <value>Report an Issue</value> 2197 </data> 2198 <data name="LangAlign_Return BTW, notice that the file cuts off right at the end of that "n" in "LangAlign_Return". The string should read "LangAlign_ReturnToWorkspace". The file should also end at line 2222.

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• Jumping onto next string when the condition is met

  - by user98235

  This was a problem related to one of the past topcoder exam problems called HowEasy. Let's assume that we're given a sentence, for instance, "We a1re really awe~~~some" I just wanted to take get rid of every word in the sentence that doesn't contain alphabet characters, so in the above sentence, the desired output would be "We really" The below is the code I wrote (incomplete), and I don't know how to move on to the next string when the condition (the string contains a character that's not alphabet) is met. Could you suggest some revisions or methods that would allow me to do that? vect would be the vector of strings containing the desired output string param; cin>>param; stringstream ss(param); vector<string> vect; string c; while(ss >> c){ for(int i=0; i < c.length(); i++){ if(!(97<=int(c[i])&&int(c[i])<=122) && !(65<=int(c[i])&&int(c[i])<=90)){ //I want to jump onto next string once the above condition is met //and ignore string c; } vect.push_back(c); if (ss.peek() == ' '){ ss.ignore(); } } }

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• Encode_JSON Errors in Lasso 8.6.2 After Period of Time

  - by ATP_JD

  We are in the process of converting apps from Lasso 8 to Lasso 9, and as an intermediate step, have upgraded from 8.5.5 to 8.6.2 (which runs alongside 9 on our new box, in different virtual hosts). I am finding that with 8.6.2 we are getting a slew of errors on pages that call encode_json. The weird thing with these errors is that they don't start happening until some period of time after the site starts. Then, some hours later, all encode_json calls begin to fail with error messages like this: An error occurred while processing your request. Error Information Error Message: No tag, type or constant was defined under the name "?????????????????" with arguments: array: (pair: (-find)=([\x{0020}-\x{21}\x{23}-\x{5b}\x{5d}-\x{10fff}])), (r) at: onCompare with params: 'r' at: JSON with params: 'reload', -Options=array: (-Internal) at: JSON with params: @map: (reload)=(false), (tcstring)=(LZU), (timestring)=(10:42 AM&nbsp;&nbsp;&nbsp;1442Z) at: [...].lasso with params: 'pageloadtime'='1383038310' on line: 31 at position: 1 Error Code: -9948 (Yes, those Chinese(?) characters are in the error message.) I have removed the 8.5.5 encode_json tag from LassoStartup, so we are using the correct built-in method. The encode_json method fails for any and all parameters I throw at it from simple strings to arrays of maps. Upon restarting the site, encode_json resumes working for an hour or two, seemingly depending on load. On 8.5.5, we don't have this problem. Does anyone have experience with this issue? Any advice regarding trying the 8.5.5 tag swap encode_json to see if I can override the built-in method? Maybe it will work better? Thanks in advance for your time and assistance. -Justin

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• What's so bad about building XML with string concatenation?

  - by wsanville

  In the thread What’s your favorite “programmer ignorance” pet peeve?, the following answer appears, with a large amount of upvotes: Programmers who build XML using string concatenation. My question is, why is building XML via string concatenation (such as a StringBuilder in C#) bad? I've done this several times in the past, as it's sometimes the quickest way for me to get from point A to point B when to comes to the data structures/objects I'm working with. So far, I have come up with a few reasons why this isn't the greatest approach, but is there something I'm overlooking? Why should this be avoided? Probably the biggest reason I can think of is you need to escape your strings manually, and most programmers will forget this. It will work great for them when they test it, but then "randomly" their apps will fail when someone throws an & symbol in their input somewhere. Ok, I'll buy this, but it's really easy to prevent the problem (SecurityElement.Escape to name one). When I do this, I usually omit the XML declaration (i.e. <?xml version="1.0"?>). Is this harmful? Performance penalties? If you stick with proper string concatenation (i.e. StringBuilder), is this anything to be concerned about? Presumably, a class like XmlWriter will also need to do a bit of string manipulation... There are more elegant ways of generating XML, such as using XmlSerializer to automatically serialize/deserialize your classes. Ok sure, I agree. C# has a ton of useful classes for this, but sometimes I don't want to make a class for something really quick, like writing out a log file or something. Is this just me being lazy? If I am doing something "real" this is my preferred approach for dealing w/ XML.

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• HashMap Memory Leak because of Dynamic Array

  - by Jake M

  I am attempting to create my own HashMap to understand how they work. I am using an array of Linked Lists to store the values(strings) in my hashmap. I am creating the array like this: Node** list; Instead of this: Node* list[nSize]; This is so the array can be any size at runtime. But I think I am getting a memory leak because of how I am doing this. I dont know where the error is but when I run the following simple code the .exe crashes. Why is my application crashing and how can I fix it? Note: I am aware that using a vector would be much better than an array but this is just for learning and I want to challenge myself to create the hashmap using a 'Dynamic' Array. PS: is that the correct term(Dynamic Array) for the kind of array I am using? struct Node { // to implement }; class HashMap { public: HashMap(int dynSize) { *list = new Node[dynSize]; size = dynSize; for (int i=0; i<size; i++) list[i] = NULL; cout << "END\n"; } ~HashMap() { for (int i=0; i<size; i++) delete list[i]; } private: Node** list; // I could use a vector here but I am experimenting with a pointer to an array(pointer), also its more elegant int size; }; int main() { // When I run this application it crashes. Where is my memory leak? HashMap h(5); system("PAUSE"); return 0; }

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• Designing a chain of states

  - by devoured elysium

  I want to model a kind of FSM(Finite State Machine). I have a sequence of states (let's say, from StateA to StateZ). This sequence is called a Chain and is implemented internally as a List. I will add states by the order I want them to run. My purpose is to be able to make a sequence of actions in my computer (for example, mouse clicks). (I know this has been done a zillion times). So a state is defined as a: boolean Precondition() <- Checks to see if for this state, some condition is true. For example, if I want to click in the Record button of a program, in this method I would check if the program's process is running or not. If it is, go to the next state in the chain list, otherwise, go to what was defined as the fail state (generally is the first state of them all). IState GetNextState() <- Returns the next state to evaluate. If Precondition() was sucessful, it should yield the next state in the chain otherwise it should yield the fail state. Run() Simply checks the Precondition() and sets the internal data so GetNextState() works as expected. So, a naive approach to this would be something like this: Chain chain = new Chain(); //chain.AddState(new State(Precondition, FailState, NextState) <- Method structure chain.AddState(new State(new WinampIsOpenCondition(), null, new <problem here, I want to referr to a state that still wasn't defined!>); The big problem is that I want to make a reference to a State that at this point still wasn't defined. I could circumvent the problem by using strings when refrering to states and using an internal hashtable, but isn't there a clearer alternative? I could just pass only the pre-condition and failure states in the constructor, having the chain just before execution put in each state the correct next state in a public property but that seems kind of awkward.

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• Is there a way to find out whether a class is a direct base of another class?

  - by user176168

  Hi I'm wondering whether there is a way to find out whether a class is a direct base of another class i.e. in boost type trait terms a is_direct_base_of function. As far as I can see boost doesn't see to support this kind of functionality which leads me to think that its impossible with the current C++ standard. The reason I want it is to do some validation checking on two macro's that are used for a reflection system to specify that one class is derived from another e.g. header.h: #define BASE A #define DERIVED B class A {}; class B : public A { #include <rtti.h> }; rtti.h: // I want to check that the two macro's are correct with a compile time assert Rtti<BASE, DERIVED> m_rtti; Although the macro's seem unnecessary in this simple example in my real world scenario rtti.h is a lot more complex. One possible avenue would be to compare the size of the this pointer with the size of a this pointer cast to the base type and some how trying to figure out whether its the size of the base class itself away or something (yeah your right I don't know how that would work either! lol)

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• iPhone inputting NSUserDefaults into a UITextField

  - by Rob

  I am writing a program where I where the first time a user runs it - they will have to fill out about 10 different UITextFields. I am trying to save the fields so that on subsequent runs of the program that whatever they previously put will already be displayed in those UITextFields so the wont have to re-input it in - unless they want to edit something in which case they still have that option. I think that I have figured out a good way to save the strings using NSUserDefaults but now I am trying to figure out how to have those fields populate a UITextField - it doesnt seem as easy as if they were UILabels. This is the route I am attempting: // in the viewDidLoad portion. NSUserDefaults *userData = [NSUserDefaults standardUserDefaults]; //Hooks. NSString *placeHolderName = [userData stringForKey:@"name"]; txtName.text = @"%@", placeHolderName; When I do this, it simply displays the '%@' in the textfields. I want whatever variable being held by placeHolderName to be automatically put into that UITextField. Is this possible?

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• What are CAD apps written in, and how are they organized ?

  - by ldigas

  What are CAD applications (Rhino, Autocad) of today written in and how are they organized internally ? I gave as an example, Autocad and Rhino, although I would love to hear of other examples as well. I'm particularly interested in knowing what is their backend written in (multilanguage ?) and how is it organized, and how do they handle their frontend (GUI) in real time ? Do they use native windows API's or some libraries of their own, since I imagine, as good as may be, the open source solutions on today's market won't cut it. I may be wrong ... As most of you who have used them know, they handle amongs other things relatively complex rotational operations in realtime (shading is not interesting me). I've been doing some experiments with several packages recently, and for some larger models found that there is considerable difference in speed in, for example, programed rotation (big full ship models) amongst some of them (which I won't name). So I'm wondering about their internals ... Also, if someone knows of some book on the subject, I'd be interested to hear of it.

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• Best practices for (over)using Azure queues

  - by John

  Hi, I'm in the early phases of designing an Azure-based application. One of the things that attracts me to Azure is the scalability, given the variability of the demand I'm likely to expect. As such I'm trying to keep things loosely coupled so I can add instances when I need to. The recommendations I've seen for architecting an application for Azure include keeping web role logic to a minimum, and having processing done in worker roles, using queues to communicate and some sort of back-end store like SQL Azure or Azure Tables. This seems like a good idea to me as I can scale up either or both parts of the application without any issue. However I'm curious if there are any best practices (or if anyone has any experiences) for when it's best to just have the web role talk directly to the data store vs. sending data by the queue? I'm thinking of the case where I have a simple insert to do from the web role - while I could set this up as a message, send it on the queue, and have a worker role pick it up and do the insert, it seems like a lot of double-handling. However I also appreciate that it may be the case that this is better in the long run, in case the web role gets overwhelmed or more complex logic ends up being required for the insert. I realise this might be a case where the answer is "it depends entirely on the situation, check your perf metrics" - but if anyone has any thoughts I'd be very appreciative! Thanks John

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• Modify Gridview as it's being rendered through javascript

  - by JonF

  I'm trying to modify a field in each row of my gridview as it is rendered. I need to modify it with client side Javascript. I'm somewhat new to asp.net, but I think I should be doing something with clientscriptmanager. I came up with a simple scenario which is basically what I want to do to avoid getting bogged down in the details. If I could accomplish the following I could accomplish my goal. Say I have a grid view of names and salaries. I want to double each persons salary before displaying it. Obviously I can do it in the code behind, but due to the nature of the more complex actual thing I'm doing, I need to do it in javascript <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" onrowdatabound="GridView1_RowDataBound" > <Columns> <asp:BoundField HeaderText="Full Name" DataField="Name" ></asp:BoundField> <asp:BoundField HeaderText="Salary" DataField="Salary" /> </Columns>

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• How to write an R function that evaluates an expression within a data-frame

  - by Prasad Chalasani

  Puzzle for the R cognoscenti: Say we have a data-frame: df <- data.frame( a = 1:5, b = 1:5 ) I know we can do things like with(df, a) to get a vector of results. But how do I write a function that takes an expression (such as a or a > 3) and does the same thing inside. I.e. I want to write a function fn that takes a data-frame and an expression as arguments and returns the result of evaluating the expression "within" the data-frame as an environment. Never mind that this sounds contrived (I could just use with as above), but this is just a simplified version of a more complex function I am writing. I tried several variants ( using eval, with, envir, substitute, local, etc) but none of them work. For example if I define fn like so: fn <- function(dat, expr) { eval(expr, envir = dat) } I get this error: > fn( df, a ) Error in eval(expr, envir = dat) : object 'a' not found Clearly I am missing something subtle about environments and evaluation. Is there a way to define such a function?

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• Getting dialogue snippets from text using regular expressions

  - by sheldon

  I'm trying to extract snippets of dialogue from a book text. For example, if I have the string "What's the matter with the flag?" inquired Captain MacWhirr. "Seems all right to me." Then I want to extract "What's the matter with the flag?" and "Seem's all right to me.". I found a regular expression to use here, which is "[^"\\]*(\\.[^"\\]*)*". This works great in Eclipse when I'm doing a Ctrl+F find regex on my book .txt file, but when I run the following code: String regex = "\"[^\"\\\\]*(\\\\.[^\"\\\\]*)*\""; String bookText = "\"What's the matter with the flag?\" inquired Captain MacWhirr. \"Seems all right to me.\""; Pattern p = Pattern.compile(regex); Matcher m = p.matcher(bookText); if(m.find()) System.out.println(m.group(1)); The only thing that prints is null. So am I not converting the regex into a Java string properly? Do I need to take into account the fact that Java Strings have a \" for the double quotes?

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• Object Design catalog and resources

  - by Tauren

  I'm looking for web sites, books, or other resources that provide a catalog of object designs used in common scenarios. I'm not looking for generic design patterns, but for samples of actual object designs that were used to solve real problems. For instance, I'm about to build an internal messaging system for a web application, similar to Facebook's messaging system. This system will allow administrators to send messages to all members, to selected groups of members, or to individuals. Members can send messages to other members or groups of members. Fairly common stuff and a feature that I'm sure thousands of web applications require. I know each situation is different and there are a million ways to design this solution. Although this scenario isn't really all that complex, I'm sure the basic design of the necessary objects and relationships for a system like this has already been done many times. It would be nice to review other similar designs before building my own. Is there a place where people can share their designs and others can browse/search through the catalog to review and provide feedback on them? StackOverflow could be used to a degree for this, but doesn't really provide a catalog of designs. Any other resources that would relate?

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• Four-color theorem in Prolog (using a dynamic predicate)

  - by outa

  Hi, I'm working on coloring a map according to the four-color theorem (http://en.wikipedia.org/wiki/Four_color_theorem) with SWI-Prolog. So far my program looks like this: colour(red). colour(blue). map_color(A,B,C) :- colour(A), colour(B), colour(C), C \= B, C \= A. (the actual progam would be more complex, with 4 colors and more fields, but I thought I'd start out with a simple case) Now, I want to avoid double solutions that have the same structure. E.g. for a map with three fields, the solution "red, red, blue" would have the same structure as "blue, blue, red", just with different color names, and I don't want both of them displayed. So I thought I would have a dynamic predicate solution/3, and call assert(solution(A,B,C)) at the end of my map_color predicate. And then, for each solution, check if they already exist as a solution/3 fact. The problem is that I would have to assert something like solution(Color1,Color1,Color2), i.e. with variables in order to make a unification check. And I can't think of a way to achieve this. So, the question is, what is the best way to assert a found solution and then make a unification test so that "red, red, blue" would unify with "blue, blue, red"?

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• DBD::CSV: Problem with userdefined functions

  - by sid_com

  From the SQL::Statement::Functions documentation: Creating User-Defined Functions ... More complex functions can make use of a number of arguments always passed to functions automatically. Functions always receive these values in @_: sub FOO { my( $self, $sth, $rowhash, @params ); } #!/usr/bin/env perl use 5.012; use warnings; use strict; use DBI; my $dbh = DBI->connect( "DBI:CSV:", undef, undef, { RaiseError => 1, } ); my $table = 'wages'; my $array_ref = [ [ 'id', 'number' ], [ 0, 6900 ], [ 1, 3200 ], [ 2, 1800 ], ]; $dbh->do( "CREATE TEMP TABLE $table AS import( ? )", {}, $array_ref ); sub routine { my $self = shift; my $sth = shift; my $rowhash = shift; # return $_[0] / 30; }; $dbh->do( "CREATE FUNCTION routine" ); my $sth = $dbh->prepare( "SELECT id, routine( number ) AS result FROM $table" ); $sth->execute(); $sth->dump_results(); When I try this I get an error-message: DBD::CSV::st execute failed: Use of uninitialized value $_[0] in division (/) at ./so.pl line 27. [for Statement "SELECT id, routine( number ) AS result FROM "wages""] at ./so.pl line 34. When I comment out the third argument I works as expected ( because it looks as if the third argument is missing ): #!/usr/bin/env perl ... sub routine { my $self = shift; my $sth = shift; #my $rowhash = shift; return $_[0] / 30; }; ... 0, 230 1, 106.667 2, 60 3 rows Is this a bug?

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