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• How to read from USB without any driver ?

  - by YouKnowWho

  We are creating small system which has GPS receiver and PC. We want to test my GPS receiver, We do not want to go for a driver on the first go. First I would like to test my circuit works or nor. GPS IC has been set to output NMEA sentence. We want a program which just reads data from USB port and print it on the screen. Can we write something like this easily ? Do we have any open source tool which will achieve this purpose ? Platform : Windows 7

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• Using Rails, how can I set my primary key to not be an integer-typed column?

  - by Rudd Zwolinski

  I'm using Rails migrations to manage a database schema, and I'm creating a simple table where I'd like to use a non-integer value as the primary key (in particular, a string). To abstract away from my problem, let's say there's a table employees where employees are identified by an alphanumeric string, e.g. "134SNW". I've tried creating the table in a migration like this: create_table :employees, {:primary_key => :emp_id} do |t| t.string :emp_id t.string :first_name t.string :last_name end What this gives me is what seems like it completely ignored the line t.string :emp_id and went ahead and made it an integer column. Is there some other way to have rails generate the PRIMARY_KEY constraint (I'm using PostgreSQL) for me, without having to write the SQL in an execute call? NOTE: I know it's not best to use string columns as primary keys, so please no answers just saying to add an integer primary key. I may add one anyway, but this question is still valid.

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• Address of array vs. address of array[0] - C language

  - by user324994

  My question is why does the address of an array differ from the address of its first position? I'm trying to write my own malloc, but to start out I'm just allocating a chunk of memory and playing around with the addresses. My code looks roughly like this: #define BUFF_SIZE 1024 static char *mallocbuff; int main(){ mallocbuff = malloc(BUFF_SIZE); printf("The address of mallocbuff is %d\n", &mallocbuff); printf("The address of mallocbuff[0] is %d\n", &mallocbuff[0]); } &mallocbuff is the same address every time I run it. &mallocbuff[0] is some random address every time. I was expecting the addresses to match each other. Can anyone explain why this isn't the case?

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• VB.NET encoding one character wrong

  - by Nick Spiers

  I have a byte array that I'm encoding to a string: Private Function GetKey() As String Dim ba() As Byte = {&H47, &H43, &H44, &H53, &H79, &H73, &H74, &H65, &H6D, &H73, &H89, &HA, &H1, &H32, &H31, &H36} Dim strReturn As String = Encoding.ASCII.GetString(ba) Return strReturn End Function Then I write that to a file via IO.File.AppendAllText. If I open that file in 010 Editor (to view the binary data) it displays as this: 47 43 44 53 79 73 74 65 6D 73 3F 0A 01 32 31 36 The original byte array contained 89 at position 11, and the encoded string contains 3F. If I change my encoding to Encoding.Default.GetString, it gives me: 47 43 44 53 79 73 74 65 6D 73 E2 80 B0 0A 01 32 31 36 Any help would be much appreciated!

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• Scala, make my loop more functional

  - by Pengin

  I'm trying to reduce the extent to which I write Scala (2.8) like Java. Here's a simplification of a problem I came across. Can you suggest improvements on my solutions that are "more functional"? Transform the map val inputMap = mutable.LinkedHashMap(1->'a',2->'a',3->'b',4->'z',5->'c') by discarding any entries with value 'z' and indexing the characters as they are encountered First try var outputMap = new mutable.HashMap[Char,Int]() var counter = 0 for(kvp <- inputMap){ val character = kvp._2 if(character !='z' && !outputMap.contains(character)){ outputMap += (character -> counter) counter += 1 } } Second try (not much better, but uses an immutable map and a 'foreach') var outputMap = new immutable.HashMap[Char,Int]() var counter = 0 inputMap.foreach{ case(number,character) => { if(character !='z' && !outputMap.contains(character)){ outputMap2 += (character -> counter) counter += 1 } } }

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• Design pattern: Polymorphism for list of objects

  - by ziang

  Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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• Any way to find out which line break char(s) to use in Javascript?

  - by Irro

  I'm trying to parse some text into a textarea control and at the same time replace all with ordinary line break chars. I have been able to do it in windows by replacing with CR (it didn't work with CRLF strangely enough, it gave me linebreak + empty space) but I'm afraid that this code won't work in Unix/Mac because they use LF for line break. Is there any way to use the system default line break char in javascript? Something similar to Environment.NewLine in .Net (I wasn't able to write backslash in this editor but I use /r for CR and /n for LF, replace / with backslash)

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• LINQ query with specified number of rows in a subquery problem

  - by John

  I'm trying to write the following query in LINQ, but can't seem to get it correct. select p.* from Person p inner join PersoniPhones i ON p.PersonID = i.PersonID where p.PersonID in ( SELECT PersonID FROM ( SELECT Top 10 PersonID, iPhoneID FROM iPhone ORDER BY LastPlayedDate DESC ) as t ) I've tried the following, but it doesn't return correctly var tenIPhones = from i in context.PersonIPhones .OrderByDescending(i => i.LastPlayedDate) .Take(minNumQuestions) select new { i.PersonID, i.IPHoneID}; var people = from p in context.Person join t in tenIPhones on p.PersonID equals t.PersonID select p; Any ideas?

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• antlr: Best practice to integrate generated parser into the system

  - by green

  Here is the background, I am trying to create a DSL to allow customer write simple scripts to query into our mongodb based database. I choose antlr to implement the DSL. From my understanding (and pls let me know if it's not correct) there are 2 approaches to integrate antlr generated parser into the system: Embed code into the grammar file so that the generated parser could be used directly to make query to the database and return result in a certain format (e.g. json encoded) Keep the parser purely a parser, after feed the DSL file to it, and construct the query in another class by retrieving the AST from generated parser class So antlrers, which one do you think is the way I as an antlr newbie should go? Can you list the pros and cos of each approach, or you have other way to recommend?

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• Create an Action<T> to "set" a property, when I am provided with the LINQ Expression for the "get"

  - by Alex

  I'd like to be able to generate a compiled expression to set a property, given the lambda expression that provides the "get" method for a property. Here's what I'm looking for: public Action<int> CreateSetter<T>(Expression<Func<T, int>> getter) { // returns a compiled action using the details of the getter expression tree, or null // if the write property is not defined. } I'm still trying to understand the various types of Expression classes, so if you can point me in the right direction that would be great.

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• Good real-world uses of metaclasses (e.g. in Python)

  - by Carles Barrobés

  I'm learning about metaclasses in Python. I think it is a very powerful technique, and I'm looking for good uses for them. I'd like some feedback of good useful real-world examples of using metaclasses. I'm not looking for example code on how to write a metaclass (there are plenty examples of useless metaclasses out there), but real examples where you have applied the technique and it was really the appropriate solution. The rule is: no theoretical possibilities, but metaclasses at work in a real application. I'll start with the one example I know: Django models, for declarative programming, where the base class Model uses a metaclass to fill the model objects of useful ORM functionality from the attribute definitions. Looking forward to your contributions.

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• Haskell, list of natural number

  - by Hellnar

  Hello, I am an absolute newbie in Haskell yet trying to understand how it works. I want to write my own lazy list of integers such as [1,2,3,4,5...]. For list of ones I have written ones = 1 : ones and when tried, works fine: *Main> take 10 ones [1,1,1,1,1,1,1,1,1,1] How can I do the same for increasing integers ? I have tried this but it indeed fails: int = 1 : head[ int + 1] And after that how can I make a method that multiplies two streams? such as: mulstream s1 s2 = head[s1] * head[s2] : mulstream [tail s1] [tail s2]

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• Inserting a number into a sorted array!

  - by Jay

  I would like to write a piece of code for inserting a number into a sorted array at the appropriate position (i.e. the array should still remain sorted after insertion) My data structure doesn't allow duplicates. I am planning to do something like this: 1. Find the right index where I should be putting this element using binary search 2. Create space for this element, by moving all the elements from that index down. 3. Put this element there. Is there any other better way?

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• How do I have my apps dialog box pop up and take focus from the current running app?

  - by simba

  I know this type of thing is looked negatively upon but I write software for people with disabilities and sometimes good gui practices don't make sense. In this case, the user interacts with a assistive interface and under certain conditions, my control app needs to prompt the user with a question. My background process creates a dialog (I'm using wxwidgets wxDialog class) and calls Show(). The dialog box appears but it does not have focus (the application that the user was previously using keeps it). Since my users can't use mice, they can't simply click on the window. I've tried calling show and then followed by SetFocus(HWND) but that doesn't do it. What's the problem? Is this even possible? Window7. I'm thinking that it might have something to do with it being a dialog and not a full window (wxFrame). Any help is greatly appreciated.

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• Best practice to detect iPhone app only access for web services?

  - by Gaius Parx

  I am developing an iPhone app together with web services. The iPhone app will use GET or POST to retrieve data from the web services such as http://www.myserver.com/api/top10songs.json to get data for top ten songs for example. There is no user account and password for the iPhone app. What is the best practice to ensure that only my iPhone app have access to the web API http://www.myserver.com/api/top10songs.json? iPhone SDK's UIDevice uniqueueIdentifier is not sufficient as anyone can fake the device id as parameter making the API call using wget, curl or web browsers. The web services API will not be published. The data of the web services is not secret and private, I just want to prevent abuse as there are also API to write some data to the server such as usage log.

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• Creating a 2d matrix from an array (java)

  - by anna

  I'm supposed to write a method that creates a 2d matrix from an array, for instance: ({1, 2, 3, 4}, 3) should return the matrix {{1, 2, 3}, {4}} public class Matrix { public static int[][]toM(int[] array, int a) { int[][]matrix = new int [(array.length + a- 1)/ a][a]; for (int i = 0; i < array.length; i++){ int value = array[i]; value = value++; for (int row = 0; row < (array.length + a- 1)/a; row++) { for (int col = 0; col < a; col++) { matrix[row][col]= value++; } } } return matrix; } } I'm getting [[4, 5, 6], [7, 8, 9]]?

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• Is Android IPC plumbing exposed in any official and/or supported way?

  - by mathrick

  I'm interested in knowing how much the IPC mechanisms are meant to be exposed to the outside world. That is, if I wanted to impersonate a dalvik VM instance without having my app actually written in Java, am I allowed to do so, or will the protocol change the next time I look away from the screen? If it's allowed, what are the stability guarantees or lack thereof? Is there anything like documentation, or am I supposed just to read the fine sources on android.git.kernel.org? The purpose of it all would be to write apps in !Java languages while retaining the ability to construct GUIs. I don't care or mind if the code is technically inside a dalvik process as a JNI callout, what I'm interested in is "if I'm really good at pretending I'm Java over the wire, can I do everything actual Java code can? Or is there something that's only available as Java bytecode and nothing else?"

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• MVC 2 ViewContenxt. Writer doesn't exist in MVC 1?

  - by DaveDev

  I had the following code in an ASP.NET MVC 2 application. internal TextWriter _writer; // some stuff _writer = _viewContext.Writer; _writer.Write(_tag.ToString(TagRenderMode.EndTag)); I tried to move it to MVC 1 & now it doesn't build any more. I'm getting this error: 'System.Web.Mvc.ViewContext' does not contain a definition for 'Writer' Can someone point out how I can resolve this? Thanks.

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• Doing a UNION ALL on two different COUNTs using Linq-To-Sql

  - by Danno

  Is it possible to write a linq-to-sql statement that will return two different COUNTs that have been put into a single dataset using UNION ALL? I know this is syntactically wrong but here's what I'm trying to do: (from t1 in TableOne select t1).Count().Union( (from t2 in TableTwo select t2).Count() ) Here's the sql I would like would like to have generated: select count(*) from TableOne union all select count(*) from TableTwo I realize that Count() returns an int and does not have a Union method on it and therein lies my question. Can Linq-to-Sql be written that will achieve what I'm after?

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• Compiler: Translation to assembly

  - by sub

  I've written an interpreter for my experimental language and know I want to move on and write a small compiler for it. It will probably take the source, go through the same steps as the interpreter (tokenizer, parser) and then translate the source to assembly. Now my questions: Can I expect that every command in my language can be 1:1 translated to a bunch of assembly instructions? What I mean is if I will have to completely throw over the whole input program or if it is just translated to assembly per line. Which assembler should I use as output format?

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• What motivates people to learn a new programming language?

  - by szabgab

  There are plenty of question asking Which Programming Language Should I Learn? but I have not found an answer yet to the question what really motivates people to learn a specific new language?. There are the people who think they should learn a new language every year for educational purpose. How do they decide on the languages to be learned? Then I guess there are people who learn a new language because people around them told it is a fun language and they can build nice things with it. Of course if the current job requires it people would learn a new language but I think if the language seems to have a potential to earn money (e.g. There are plenty of jobs in Java or ObjectiveC can be used to write apps for the iPhone and make money). So why are you learning a new language or why have you learned the languages you know?

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• Making a many-to-many relationship using DataRelations object

  - by dotnetdev

  Hi, I have about 200 tables which need to relate to another table in a many-to-many fashion. I have the tables (including the intersection table) ready IN SQL Server. How can I write code using the data relation object to make the relationship? The tables are: PartStatPartName PartsMaterialsIntersection << Materials The materials table needs to have a foreign key from the PartStatPartName table. I tried various approaches using the DataRelation class but the change did not sync to SQL Server, despite being connected and adding the relation, and then calling AcceptChanges() on the dataset. Any guidance much appreciated. I have seen some threads covering the same problem but need an example in code so I can follow the right method. Thanks

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• How to find hidden properties/methods in Javascript objects?

  - by ramanujan

  I would like to automatically determine all of the properties (including the hidden ones) in a given Javascript object, via a generalization of this function: function keys(obj) { var ll = []; for(var pp in obj) { ll.push(pp); } return ll; } This works for user defined objects but fails for many builtins: repl> keys({"a":10,"b":2}); // ["a","b"] repl> keys(Math) // returns nothing! Basically, I'd like to write equivalents of Python's dir() and help(), which are really useful in exploring new objects. My understanding is that only the builtin objects have hidden properties (user code evidently can't set the "enumerable" property till HTML5), so one possibility is to simply hardcode the properties of Math, String, etc. into a dir() equivalent (using the lists such as those here). But is there a better way?

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• Sharing config settings between 2 cocoa apps

  - by bitboxer

  I am new to cocoa development and want to create a little app. For that app I need a background worker that is running all the time and a prefpane-app that gives the user the opportunity to change the settings for that background worker. The gui for the prefpane is ready, the background worker is ready, too. One of the few missing things is how to share the preferences between both apps. How do I notify the worker about changes of the preferences? And how do I store it in a way that both can read/write to it?

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• Unit testing task queues in AppEngine

  - by Swizec Teller

  For a very long time now I've been using task queues on AppEngine to schedule tasks, just the way I'm supposed to. But what I've always been wondering is how does one write tests for that? Until now I've simply made tests to make sure an error doesn't occur on the API that queues a task and then wrote the more proper tests for the API executing the task. However lately I've started feeling a bit unsatisfied by this and I'm searching for a way to actually test that the correct task has been added to the correct queue. Hopefully this can be done better than simply by deploying the code and hoping for the best. I'm using django-nonrel, if that has any bearing on the answer. To recap: How can a unit test be written to confirm tasks have been queued?

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