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• dealing cards in Clojure

  - by Ralph

  I am trying to write a Spider Solitaire player as an exercise in learning Clojure. I am trying to figure out how to deal the cards. I have created (with the help of stackoverflow), a shuffled sequence of 104 cards from two standard decks. Each card is represented as a (defstruct card :rank :suit :face-up) The tableau for Spider will be represented as follows: (defstruct tableau :stacks :complete) where :stacks is a vector of card vectors, 4 of which contain 5 cards face down and 1 card face up, and 6 of which contain 4 cards face down and 1 card face up, for a total of 54 cards, and :complete is an (initially) empty vector of completed sets of ace-king (represented as, for example, king-hearts, for printing purposes). The remainder of the undealt deck should be saved in a ref (def deck (ref seq)) During the game, a tableau may contain, for example: (struct-map tableau :stacks [[AH 2C KS ...] [6D QH JS ...] ... ] :complete [KC KS]) where "AH" is a card containing {:rank :ace :suit :hearts :face-up false}, etc. How can I write a function to deal the stacks and then save the remainder in the ref?

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• Vertex Buffers in opengl

  - by JB

  I'm making a small 3d graphics game/demo for personal learning. I know d3d9 and quite a bit about d3d11 but little about opengl at the moment so I'm intending to abstract out the actual rendering of the graphics so that my scene graph and everything "above" it needs to know little about how to actually draw the graphics. I intend to make it work with d3d9 then add d3d11 support and finally opengl support. Just as a learning exercise to learn about 3d graphics and abstraction. I don't know much about opengl at this point though, and don't want my abstract interface to expose anything that isn't simple to implement in opengl. Specifically I'm looking at vertex buffers. In d3d they are essentially an array of structures, but looking at the opengl interface the equivalent seems to be vertex arrays. However these seem to be organised rather differently where you need a separate array for vertices, one for normals, one for texture coordinates etc and set the with glVertexPointer, glTexCoordPointer etc. I was hoping to be able to implement a VertexBuffer interface much like the the directx one but it looks like in d3d you have an array of structures and in opengl you need a separate array for each element which makes finding a common abstraction quite hard to make efficient. Is there any way to use opengl in a similar way to directx? Or any suggestions on how to come up with a higher level abstraction that will work efficiently with both systems?

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• Generic callbacks

  - by bobobobo

  Extends So, I'm trying to learn template metaprogramming better and I figure this is a good exercise for it. I'm trying to write code that can callback a function with any number of arguments I like passed to it. // First function to call int add( int x, int y ) ; // Second function to call double square( double x ) ; // Third func to call void go() ; The callback creation code should look like: // Write a callback object that // will be executed after 42ms for "add" Callback<int, int, int> c1 ; c1.func = add ; c1.args.push_back( 2 ); // these are the 2 args c1.args.push_back( 5 ); // to pass to the "add" function // when it is called Callback<double, double> c2 ; c2.func = square ; c2.args.push_back( 52.2 ) ; What I'm thinking is, using template metaprogramming I want to be able to declare callbacks like, write a struct like this (please keep in mind this is VERY PSEUDOcode) <TEMPLATING ACTION <<ANY NUMBER OF TYPES GO HERE>> > struct Callback { double execTime ; // when to execute TYPE1 (*func)( TYPE2 a, TYPE3 b ) ; void* argList ; // a stored list of arguments // to plug in when it is time to call __func__ } ; So for when called with Callback<int, int, int> c1 ; You would automatically get constructed for you by < HARDCORE TEMPLATING ACTION > a struct like struct Callback { double execTime ; // when to execute int (*func)( int a, int b ) ; void* argList ; // this would still be void*, // but I somehow need to remember // the types of the args.. } ; Any pointers in the right direction to get started on writing this?

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• ARM Assembly - Converting Endianness

  - by SoulBeaver

  Hello people! This is currently a homework project that me and my teammate are stuck on. We haven't been given much of an introduction into Assembly, and this is supposed to be our first homework exercise. The task is to create a program that converts 0xAABBCCDD into 0xDDCCBBAA. I'm not looking for an answer, as that would defeat the purpose, but we are getting severely frustrated over the difficulty of this stupid thing. We think we have a good start in creating a viable solution, but we just cannot come up with the rest of the program. First, we mask every single tupel (aa), (bb), (cc), (dd) into a different register: LDR R0, LittleEndian // 0xAABBCCDD AND R1, R0, #0xFF000000 // 0xAA AND R2, R0, #0x00FF0000 // 0xBB AND R3, R0, #0x0000FF00 // 0xCC AND R4, R0, #0x000000FF // 0xDD Then we try to re-align them into the R0 register, but hell if we could come up with a good solution... Our best effort came from: ORR R0, R1, LSL #24 ORR R0, R2, LSL #8 ORR R0, R3, LSR #8 ORR R0, R4, LSR #24 which produced 0xBBBBCCDD for some odd reason; we really don't know. Any hints would be greatly appreciated. Again, we are asking for help, but not for a solution. Cheers!

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• Newb Question: scanf() in C

  - by riemannliness

  So I started learning C today, and as an exercise i was told to write a program that asks the user for numbers until they type a 0, then adds the even ones and the odd ones together. Here is is (don't laugh at my bad style): #include <stdio.h>; int main() { int esum = 0, osum = 0; int n, mod; puts("Please enter some numbers, 0 to terminate:"); scanf("%d", &n); while (n != 0) { mod = n % 2; switch(mod) { case 0: esum += n; break; case 1: osum += n; } scanf("%d", &n); } printf("The sum of evens:%d,\t The sum of odds:%d", esum, osum); return 0; } My question concerns the mechanics of the scanf() function. It seems that when you enter several numbers at once separated by spaces (eg. 1 22 34 2 8), the scanf() function somehow remembers each distinct numbers in the line, and steps through the while loop for each one respectively. Why/how does this happen? Example interaction within command prompt: - Please enter some numbers, 0 to terminate: 42 8 77 23 11 (enter) 0 (enter) - The sum of evens:50, The sum of odds:111 I'm running the program through the command prompt, it's compiled for win32 platforms with visual studio.

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• Returning an array of culture formatted dates C# MVC3

  - by user1875797

  I'm new to programming and trying to do an exercise that formats a date to the Thai culture in a variety of formats this is what I have for my code so far: public String[] FormatAsSpecified(DateTime theDate, String theCulture, String[] formats) { String[] dateResults = new String[formats.Length]; CultureInfo culture = CultureInfo.GetCultureInfo(theCulture); for (int i = 0; i < formats.Length; i++) { String culture_formatted_date = theDate.ToString(formats[i], culture); dateResults[i] = culture_formatted_date; } return dateResults; } This is the test method that goes with it: [TestMethod] public void FormatAsSpecifiedReturnsDateLiteralsInSpecifiedFormatForAllStandardFormatStrings() { //Arrange var controller = new DateController(); var theDate = new DateTime(2014, 2, 14, 9, 15, 32, 376); String theCulture = "th-TH"; // Array of all supported standard date and time format specifiers. String[] formats = { "d", "D", "f", "F", "g", "G", "m", "o", "r", "s", "t", "T", "u", "U", "Y" }; //Corresponding date literals for the standard Thai regional settings String[] expectedResults = {"14/2/2557" , "14 ?????????? 2557" , "14 ?????????? 2557 9:15" , "14 ?????????? 2557 9:15:32" , "14/2/2557 9:15" , "14/2/2557 9:15:32" , "14 ??????????" , "2014-02-14T09:15:32.3760000" , "Fri, 14 Feb 2014 09:15:32 GMT" , "2014-02-14T09:15:32" , "9:15" , "9:15:32" , "2014-02-14 09:15:32Z" , "??????????? 14 ?????????? 2014 9:15:32" , "?????????? 2557"}; //Act String[] actualResults = new String[15]; for (int i = 0; i < formats.Length; i++) { actualResults[i] = controller.FormatAsSpecified(theDate, theCulture, formats[i]); } //Assert CollectionAssert.AreEqual(expectedResults, actualResults); } I get an error in the test method at 'controller.FormatAsSpecified(theDate, theCulture, formats[i]);' that says "Argument 3, cannot convert from 'string' to 'string[]'" What am I doing wrong?

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• Custom Swing component: questions on approach

  - by phatmanace

  Hi Folks, I'm trying to build a new java swing component, I realise that I might be able to find one that does what I need on the web, but this is partly an exercise for me to learn ow to do this. I want to build a swing component that represents a Gantt chart. it would be good (though not essential for people to be able to interact with it (e.g slide the the tasks around to adjust timings) it feels like the best approach for this is to subclass JComponent, and override PaintComponent() to 'draw a picture' of what the chart should look like, as opposed to doing something like trying to jam everything into a custom JTable. I've read a couple of books on the subject, and also looked at a few examples (most notably things like JXGraph) - but I'm curious about a few things When do I have to switch to using UI delegates, and when can I stick to just fiddling around in paintcomponent() to render what I want? if I want other swing components as sub-elements of my component (e.g I wanted a text box on my gantt chart) can I no longer use paintComponent()? can I arbitrarily position them within my Gantt chart, or do I have to use a normal swing layout manager many thanks in advance. -Ace

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• Copying contents of a MySQL table to a table in another (local) database

  - by Philip Eve

  I have two MySQL databases for my site - one is for a production environment and the other, much smaller, is for a testing/development environment. Both have identical schemas (except when I am testing something I intend to change, of course). A small number of the tables are for internationalisation purposes: TransLanguage - non-English languages TransModule - modules (bundles of phrases for translation, that can be loaded individually by PHP scripts) TransPhrase - individual phrases, in English, for potential translation TranslatedPhrase - translations of phrases that are submitted by volunteers ChosenTranslatedPhrase - screened translations of phrases. The volunteers who do translation are all working on the production site, as they are regular users. I wanted to create a stored procedure that could be used to synchronise the contents of four of these tables - TransLanguage, TransModule, TransPhrase and ChosenTranslatedPhrase - from the production database to the testing database, so as to keep the test environment up-to-date and prevent "unknown phrase" errors from being in the way while testing. My first effort was to create the following procedure in the test database: CREATE PROCEDURE `SynchroniseTranslations` () LANGUAGE SQL NOT DETERMINISTIC MODIFIES SQL DATA SQL SECURITY DEFINER BEGIN DELETE FROM `TransLanguage`; DELETE FROM `TransModule`; INSERT INTO `TransLanguage` SELECT * FROM `PRODUCTION_DB`.`TransLanguage`; INSERT INTO `TransModule` SELECT * FROM `PRODUCTION_DB`.`TransModule`; INSERT INTO `TransPhrase` SELECT * FROM `PRODUCTION_DB`.`TransPhrase`; INSERT INTO `ChosenTranslatedPhrase` SELECT * FROM `PRODUCTION_DB`.`ChosenTranslatedPhrase`; END When I try to run this, I get an error message: "SELECT command denied to user 'username'@'localhost' for table 'TransLanguage'". I also tried to create the procedure to work the other way around (that is, to exist as part of the data dictionary for the production database rather than the test database). If I do it that, way, I get an identical message except it tells me I'm denied the DELETE command rather than SELECT. I have made sure that my user has INSERT, DELETE, SELECT, UPDATE and CREATE ROUTINE privileges on both databases. However, it seems as though MySQL is reluctant to let this user exercise its privileges on both databases at the same time. How come, and is there a way around this?

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• django simple approach to multi-field search

  - by Scott Willman

  I have a simple address book app that I want to make searchable. The model would look something like: class Address(models.Model): address1 = models.CharField("Address Line 1", max_length=128) address2 = models.CharField("Address Line 2", max_length=128) city = models.CharField("City", max_length=128) state = models.CharField("State", max_length=24) zipCode = models.CharField("Zip Code", max_length=24) def __unicode__(self): return "%s %s, %s, %s, %s" % (self.address1, self.address2, self.city, self.state, self.zipCode) class Entry(models.Model): name = models.CharField("Official School Name", max_length=128) createdBy = models.ForeignKey(User) address = models.ForeignKey(Address, unique=True) def __unicode__(self): return "%s - %s, %s" % (self.name, self.address.city, self.address.state) I want the searching to be fairly loose, like: Bank of America Los Angeles 91345. It seems like I want a field that contains all of those elements into one that I can search, but that also seems redundant. I was hoping I could add a method to the Entry model like this: def _getSearchText(self): return "%s %s %s" % (self.name, self.address, self.mascot) searchText = property(_getSearchText) ...and search that as a field, but I suppose that's wishful thinking... How should I approach this using basic Django and SqLite (this is a learning exercise). Thank you!!

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• Why doesn't this for-loop execute?

  - by Maulrus

  I'm writing a program for an exercise that will read data from a file and format it to be readable. So far, I have a bit of code that will separate a header from the data that goes under it. Here it is: int main() { ifstream in("records.txt"); ofstream out("formatted_records.txt"); vector<string> temp; vector<string> headers; for (int i = 0; getline(in,temp[i]); ++i) { static int k = -1; if (str_isalpha(temp[i])) { headers[++k] = temp[i]; temp.erase(temp.begin() + i); } else { temp[i] += "," + headers[k]; } } } (str_isalpha() is just a function that applies isalpha() to every character in a string.) Now, the for-loop in this program doesn't execute, and I can't figure out why. Does anybody know?

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• http_access.log on WebSphere 6.1.0.29

  - by DavidG

  I am running WebSphere 6.1.0.29 and I need to track the requests being made to an Enterprise Application. Previously I did this by routing the requests through a proxy server, but I need to repeat the exercise and I figure there must be a simpler way. Does anyone know how to enable HTTP access logging? I have been through the console an thought I had enabled http_access.log and http_error.log via: Application servers server1 HTTP error and NCSA access logging (where 'server1' is the application server) I've enabled the service at startup, and ticked the boxes to enable access logging and error logging - however... nothing has happened. I have restarted the server, restarted the Enterprise apps and even did a "find . -name" for the log files - but they don't seem to be anywhere on the system. I saw on a JavaRanch thread someone suggested writing a custom filter for requests in an application, but this seems like wild overkill - plus I am doing the logs to test a pre-built binary, so I don't want to mess with the code. Anyone have any ideas/suggestions? Help! :-)

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• Populate a tree from Hierarchical data using 1 LINQ statement

  - by Midhat

  Hi. I have set up this programming exercise. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication2 { class DataObject { public int ID { get; set; } public int ParentID { get; set; } public string Data { get; set; } public DataObject(int id, int pid, string data) { this.ID = id; this.ParentID = pid; this.Data = data; } } class TreeNode { public DataObject Data {get;set;} public List<DataObject> Children { get; set; } } class Program { static void Main(string[] args) { List<DataObject> data = new List<DataObject>(); data.Add(new DataObject(1, 0, "Item 1")); data.Add(new DataObject(2, 0, "Item 2")); data.Add(new DataObject(21, 2, "Item 2.1")); data.Add(new DataObject(22, 2, "Item 2.2")); data.Add(new DataObject(221, 22, "Item 2.2.1")); data.Add(new DataObject(3, 0, "Item 3")); } } } The desired output is a List of 3 treenodes, having items 1, 2 and 3. Item 2 will have a list of 2 dataobjects as its children member and so on. I have been trying to populate this tree (or rather a forest) using just 1 SLOC using LINQ. A simple group by gives me the desired data but the challenge is to organize it in TreeNode objects. Can someone give a hint or an impossibility result for this?

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• How do I create rows with alternating colors for a UITableView on iPhone?

  - by Mat

  Hi all, i would to have alternate 2 colors of rows, like the first black, the second white, the third black, etc, etc... my approach is like a basic exercise of programming to calculate if a number is odd number or not: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; cell = ((MainCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]); if (cell==nil) { NSArray *topLevelObjects=[[NSBundle mainBundle] loadNibNamed:@"MainCell" owner:self options:nil]; for (id currentObject in topLevelObjects){ if ([currentObject isKindOfClass:[UITableViewCell class]]){ if ((indexPath.row % 2)==0) { [cell.contentView setBackgroundColor:[UIColor purpleColor]]; }else{ [cell.contentView setBackgroundColor:[UIColor whiteColor]]; } cell = (MainCell *) currentObject; break; } } }else { AsyncImageView* oldImage = (AsyncImageView*) [cell.contentView viewWithTag:999]; [oldImage removeFromSuperview]; }return cell; The problem is that when i do a rapid scroll, the background of cells become like the last 2 cell black, the first 2 cell white or something like this, but if i scroll slow works fine. I think the problem is the cache of reusableCell. Any ideas? TIA

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• Partial class or "chained inheritance"

  - by Charlie boy

  Hi From my understanding partial classes are a bit frowned upon by professional developers, but I've come over a bit of an issue; I have made an implementation of the RichTextBox control that uses user32.dll calls for faster editing of large texts. That results in quite a bit of code. Then I added spellchecking capabilities to the control, this was made in another class inheriting RichTextBox control as well. That also makes up a bit of code. These two functionalities are quite separate but I would like them to be merged so that I can drop one control on my form that has both fast editing capabilities and spellchecking built in. I feel that simply adding the code form one class to the other would result in a too large code file, especially since there are two very distinct areas of functionality, so I seem to need another approach. Now to my question; To merge these two classes should I make the spellchecking RichTextBox inherit from the fast edit one, that in turn inherits RichTextBox? Or should I make the two classes partials of a single class and thus making them more “equal” so to speak? This is more of a question of OO principles and exercise on my part than me trying to reinvent the wheel, I know there are plenty of good text editing controls out there. But this is just a hobby for me and I just want to know how this kind of solution would be managed by a professional. Thanks!

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• [C#] how to do Exception Handling & Tracing

  - by shrimpy

  Hi all, i am reading some C# books, and got some exercise don't know how to do, or not sure what does the question mean. Problem: After working for a company for some time, your skills as a knowledgeable developer are recognized, and you are given the task of “policing” the implementation of exception handling and tracing in the source code (C#) for an enterprise application that is under constant incremental development. The two goals set by the product architect are: 100% of methods in the entire application must have at least a standard exception handler, using try/catch/finally blocks; more complex methods must also have additional exception handling for specific exceptions All control flow code can optionally write “tracing” information to assist in debugging and instrumentation of the application at run-time in situations where traditional debuggers are not available (eg. on staging and production servers). (i am not quite understand these criterias, i came from the java world, java has two kind of exception, check and unchecked exception. Developer must handle checked exception, and do logging. about unchecked exception, still do logging maybe, but most of the time we just throw it. however here comes to C#, what should i do????) Question for Problem: List rules you would create for the development team to follow, and the ways in which you would enforce rules, to achieve these goals. How would you go about ensuring that all existing code complies with the rules specified by the product architect; in particular, what considerations would impact your planning for the work to ensure all existing code complies?

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• How to mock a String using mockito?

  - by Alceu Costa

  I need to simulate a test scenario in which I call the getBytes() method of a String object and I get an UnsupportedEncodingException. I have tried to achieve that using the following code: String nonEncodedString = mock(String.class); when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error.")); The problem is that when I run my test case I get a MockitoException that says that I can't mock a java.lang.String class. Is there a way to mock a String object using mockito or, alternatively, a way to make my String object throw an UnsupportedEncodingException when I call the getBytes method? Here are more details to illustrate the problem: This is the class that I want to test: public final class A{ public static String f(String str){ try{ return new String(str.getBytes("UTF-8")); } catch (UnsupportedEncodingException e) { // This is the catch block that I want to exercise. ... } } } This is my testing class (I'm using JUnit 4 and mockito): public class TestA { @Test(expected=UnsupportedEncodingException.class) public void test(){ String aString = mock(String.class); when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error.")); A.f(aString); } }

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• Issue with creating index organized table

  - by mtim

  I'm having a weird problem with index organized table. I'm running Oracle 11g standard. i have a table src_table SQL> desc src_table; Name Null? Type --------------- -------- ---------------------------- ID NOT NULL NUMBER(16) HASH NOT NULL NUMBER(3) ........ SQL> select count(*) from src_table; COUNT(*) ---------- 21108244 now let's create another table and copy 2 columns from src_table set timing on SQL> create table dest_table(id number(16), hash number(20), type number(1)); Table created. Elapsed: 00:00:00.01 SQL> insert /*+ APPEND */ into dest_table (id,hash,type) select id, hash, 1 from src_table; 21108244 rows created. Elapsed: 00:00:15.25 SQL> ALTER TABLE dest_table ADD ( CONSTRAINT dest_table_pk PRIMARY KEY (HASH, id, TYPE)); Table altered. Elapsed: 00:01:17.35 It took Oracle < 2 min. now same exercise but with IOT table SQL> CREATE TABLE dest_table_iot ( id NUMBER(16) NOT NULL, hash NUMBER(20) NOT NULL, type NUMBER(1) NOT NULL, CONSTRAINT dest_table_iot_PK PRIMARY KEY (HASH, id, TYPE) ) ORGANIZATION INDEX; Table created. Elapsed: 00:00:00.03 SQL> INSERT /*+ APPEND */ INTO dest_table_iot (HASH,id,TYPE) SELECT HASH, id, 1 FROM src_table; "insert" into IOT takes 18 hours !!! I have tried it on 2 different instances of Oracle running on win and linux and got same results. What is going on here ? Why is it taking so long ?

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• How do the major C# DI/IoC frameworks compare?

  - by Slomojo

  At the risk of stepping into holy war territory, What are the strengths and weaknesses of these popular DI/IoC frameworks, and could one easily be considered the best? ..: Ninject Unity Castle.Windsor Autofac StructureMap Are there any other DI/IoC Frameworks for C# that I haven't listed here? In context of my use case, I'm building a client WPF app, and a WCF/SQL services infrastructure, ease of use (especially in terms of clear and concise syntax), consistent documentation, good community support and performance are all important factors in my choice. Update: The resources and duplicate questions cited appear to be out of date, can someone with knowledge of all these frameworks come forward and provide some real insight? I realise that most opinion on this subject is likely to be biased, but I am hoping that someone has taken the time to study all these frameworks and have at least a generally objective comparison. I am quite willing to make my own investigations if this hasn't been done before, but I assumed this was something at least a few people had done already. Second Update: If you do have experience with more than one DI/IoC container, please rank and summarise the pros and cons of those, thank you. This isn't an exercise in discovering all the obscure little containers that people have made, I'm looking for comparisons between the popular (and active) frameworks.

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• Using MATLAB's plotting features as an interactive part of a Fortran program

  - by ldigas

  Although many of you will have a decent idea of what I'm aiming at, just from reading the title -- allow me a simple introduction still. I have a Fortran program - it consists of a program, some internal subroutines, 7 modules with its own procedures, and ... uhmm, that's it. Without going into much detail, for I don't think it's necessary at this point, what would be the easiest way to use MATLAB's plotting features (mainly plot(x,y) with some customizations) as an interactive part of my program ? For now I'm using some of my own custom plotting routines (based on HPGL and Calcomp's routines), but just as part of an exercise on my part, I'd like to see where this could go and how would it work (is it even possible what I'm suggesting?). Also, how much effort would it take on my part ? I know this subject has been rather extensively described in many "tutorials" on the net, but for some reason I have trouble finding the really simple yet illustrative introductory ones. So if anyone can post an example or two, simple ones, I'd be really grateful. Or just take me by the hand and guide me through one working example. platform: IVF 11.something :) on Win XP SP2, Matlab 2008b

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• How to get OCI lib to work on red hat machine to work with R Oracle?

  - by Matt Bannert

  I need to get OCI lib working on my rhel 6.3 machine and I am experiencing some trouble with OCI headers files that can't be found. I have installed (using yum install) oracle-instantclient11.2-basic-11.2.0.3.0-1.x86_64.rpm because this official page it's all I need to run OCI. To test the whole thing in general I've installed sqplus64, which worked after I set export LD_LIBRARY_PATH=/usr/lib/oracle/11.2/client64/lib. Unfortunately the headers files couldn't be found after setting LD_LIBRARY_PATH. Actually I am not surprised because there is no include directory in any of these oracle paths. So the question is: Where do I get these missing header files from? Are they actually already there and I just can find them? Btw: I am doing this whole exercise because I want to use ROracle on my R Studio server and this R package depends on the OCI library. Once I am back in R territory the road gets much less bumpier for me. EDIT: this documentation helped me a little further. However, I guess I found some header files now in: "/usr/include/oracle/11.2/client64". But which variable do I have to set to this location?

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• routes as explained in RoR tutorial 2nd Ed?

  - by 7stud

  The author, Michael Hartl, says: Here the rule: get "static_pages/home" maps requests for the URI /static_pages/home to the home action in the StaticPages controller. How? The type of request is given, the url is given, but where is the mapping to a controller and action? My tests all pass, though. I also tried deleting all the actions in the StaticPagesController, which just looks like this: class StaticPagesController < ApplicationController def home end def about end def help end def contact end end ...and my tests still pass, which is puzzling. The 2nd edition of the book(online) is really frustrating. Specifically, the section about making changes to the Guardfile is impossible to follow. For instance, if I instruct you to edit this file: blah blah blah dog dog dog beetle beetle beetle jump jump jump and make these changes: blah blah blah . . . go go go . . . jump jump jump ...would you have any idea where the line 'go go go' should be in the code? And the hint for exercise 3.5-1 is flat out wrong. If the author would put up a comment section at the end of every chapter, the rails community could self-edit the book.

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• How do you prove a function works?

  - by glenn I.

  I've recently gotten the testing religion and have started primarily with unit testing. I code unit tests which illustrate that a function works under certain cases, specifically using the exact inputs I'm using. I may do a number of unit tests to exercise the function. Still, I haven't actually proved anything other than the function does what I expect it to do under the scenarios I've tested. There may be other inputs and scenarios I haven't thought of and thinking of edge cases is expensive, particularly on the margins. This is all not very satisfying to do me. When I start to think of having to come up with tests to satisfy branch and path coverage and then integration testing, the prospective permutations can become a little maddening. So, my question is, how can one prove (in the same vein of proving a theorem in mathematics) that a function works (and, in a perfect world, compose these 'proofs' into a proof that a system works)? Is there a certain area of testing that covers an approach where you seek to prove a system works by proving that all of its functions work? Does anybody outside of academia bother with an approach like this? Are there tools and techniques to help? I realize that my use of the word 'work' is not precise. I guess I mean that a function works when it does what some spec (written or implied) states that it should do and does nothing other than that. Note, I'm not a mathematician, just a programmer.

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• Use SQL to clone a tree structure represented in a database

  - by AmoebaMan17

  Given a table that represents a hierarchical tree structure and has three columns ID (Primary Key, not-autoincrementing) ParentGroupID SomeValue I know the lowest most node of that branch, and I want to copy that to a new branch with the same number of parents that also need to be cloned. I am trying to write a single SQL INSERT INTO statement that will make a copy of every row that is of the same main has is part one GroupID into a new GroupID. Example beginning table: ID | ParentGroupID | SomeValue ------------------------ 1 | -1 | a 2 | 1 | b 3 | 2 | c Goal after I run a simple INSERT INTO statement: ID | ParentGroupID | SomeValue ------------------------ 1 | -1 | a 2 | 1 | b 3 | 2 | c 4 | -1 | a-cloned 5 | 4 | b-cloned 6 | 5 | c-cloned Final tree structure +--a (1) | +--b (2) | +--c (3) | +--a-cloned (4) | +--b-cloned (5) | +--c-cloned (6) The IDs aren't always nicely spaced out as this demo data is showing, so I can't always assume that the Parent's ID is 1 less than the current ID for rows that have parents. Also, I am trying to do this in T-SQL (for Microsoft SQL Server 2005 and greater). This feels like a classic exercise that should have a pure-SQL answer, but I'm too used to programming that my mind doesn't think in relational SQL.

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• Tableview not drilling down

  - by JoshD

  I have a Tableview which is loaded with a dummy list of exercises. I need to drill to a different page. My didSelectRow is being called, but not implementing the method. The app is a tab bar navigation app that loads a UITableView. #import <UIKit/UIKit.h> @interface Schedule : UIViewController <UITableViewDelegate, UITableViewDataSource> { NSArray *mySchedule; } @end #import "Schedule.h" #import "AnotherViewController.h" @implementation Schedule - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{ return mySchedule.count; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{ //create a cell UITableViewCell *cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"cell"]; //fill it with contents cell.textLabel.text = [mySchedule objectAtIndex:indexPath.row]; //return it return cell; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{ AnotherViewController *anotherViewController = [[AnotherViewController alloc] initWithNibName:@"AnotherViewController" bundle:nil]; [self.navigationController pushViewController:anotherViewController animated:YES]; [anotherViewController release]; } /* // The designated initializer. Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad. - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) { // Custom initialization } return self; } */ // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { NSString *myFile = [[NSBundle mainBundle] pathForResource:@"exercise" ofType:@"plist"]; mySchedule = [[NSArray alloc] initWithContentsOfFile:myFile]; [super viewDidLoad]; }

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• Determine asymmetric latencies in a network

  - by BeeOnRope

  Imagine you have many clustered servers, across many hosts, in a heterogeneous network environment, such that the connections between servers may have wildly varying latencies and bandwidth. You want to build a map of the connections between servers my transferring data between them. Of course, this map may become stale over time as the network topology changes - but lets ignore those complexities for now and assume the network is relatively static. Given the latencies between nodes in this host graph, calculating the bandwidth is a relative simply timing exercise. I'm having more difficulty with the latencies - however. To get round-trip time, it is a simple matter of timing a return-trip ping from the local host to a remote host - both timing events (start, stop) occur on the local host. What if I want one-way times under the assumption that the latency is not equal in both directions? Assuming that the clocks on the various hosts are not precisely synchronized (at least that their error is of the the same magnitude as the latencies involved) - how can I calculate the one-way latency? In a related question - is this asymmetric latency (where a link is quicker in direction than the other) common in practice? For what reasons/hardware configurations? Certainly I'm aware of asymmetric bandwidth scenarios, especially on last-mile consumer links such as DSL and Cable, but I'm not so sure about latency. Added: After considering the comment below, the second portion of the question is probably better off on serverfault.

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