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  • Understanding how software testing works and what to test.

    - by RHaguiuda
    Intro: I've seen lots of topics here on SO about software testing and other terms I don't understand. Problem: As a beginner developer I, unfortunately, have no idea how software testing works, not even how to test a simple function. This is a shame, but thats the truth. I also hope this question can help others beginners developers too. Question: Can you help me to understand this subject a little bit more? Maybe some questions to start would help: When I develop a function, how should I test it? For example: when working with a sum function, should I test every input value possible or just some limits? How about testing functions with strings as parameters? In a big program, do I have to test every single piece of code of it? When you guys program do you test every code written? How automated test works and how can I try one? How tools for automated testing works and what they do? I`ve heard about unit testing. Can I have a brief explanation on this? What is a testing framework? If possible please post some code with examples to clarify the ideas. Any help on this topic is very welcome! Thanks.

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  • A GUID as the MySQL table's Primary Key or as a separate column

    - by Ben
    I have a multi-process program that performs, in a 2 hour period, 5-10 million inserts to a 34GB table within a single Master/Slave MySQL setup (plus an equal number of reads in that period). The table in question has only 5 fields and 3 (single field) indexes. The primary key is auto-incrementing. I am far from a DBA, but the database appears to be crippled during this two hour period. So, I have a couple of general questions. 1) How much bang will I get out of batching these writes into units of 10? Currently, I am writing each insert serially because, after writing, I immediately need to know, in my program, the resulting primary key of each insert. The PK is the only unique field presently and approximating the order of insertion with something like a Datetime field or a multi-column value is not acceptable. If I perform a bulk insert, I won't know these IDs, which is a problem. So, I've been thinking about turning the auto-increment primary key into a GUID and enforcing uniqueness. I've also been kicking around the idea of creating a new column just for the purposes of the GUID. I don't really see the what that achieves though, that the PK approach doesn't already offer. As far as I can tell, the big downside to making the PK a randomly generated number is that the index would take a long time to update on each insert (since insertion order would not be sequential). Is that an acceptable approach for a table that is taking this number of writes? Thanks, Ben

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  • Achieving Thread-Safety

    - by Smasher
    Question How can I make sure my application is thread-safe? Are their any common practices, testing methods, things to avoid, things to look for? Background I'm currently developing a server application that performs a number of background tasks in different threads and communicates with clients using Indy (using another bunch of automatically generated threads for the communication). Since the application should be highly availabe, a program crash is a very bad thing and I want to make sure that the application is thread-safe. No matter what, from time to time I discover a piece of code that throws an exception that never occured before and in most cases I realize that it is some kind of synchronization bug, where I forgot to synchronize my objects properly. Hence my question concerning best practices, testing of thread-safety and things like that. mghie: Thanks for the answer! I should perhaps be a little bit more precise. Just to be clear, I know about the principles of multithreading, I use synchronization (monitors) throughout my program and I know how to differentiate threading problems from other implementation problems. But nevertheless, I keep forgetting to add proper synchronization from time to time. Just to give an example, I used the RTL sort function in my code. Looked something like FKeyList.Sort (CompareKeysFunc); Turns out, that I had to synchronize FKeyList while sorting. It just don't came to my mind when initially writing that simple line of code. It's these thins I wanna talk about. What are the places where one easily forgets to add synchronization code? How do YOU make sure that you added sync code in all important places?

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  • Django unit testing: South-migrated DB works in MySQL, throws duplicate PK error in PostGreSQL. Am I

    - by unclaimedbaggage
    Hi folks, (Worth starting off with a disclaimer: I'm very new to PostGreSQL) I have a django site which involves a standard app/tests.py testing file. If I migrate the DB to MySQL (through South),, the tests all pass. However in PostGresQL, I'm getting the following error: IntegrityError: duplicate key value violates unique constraint "business_contact_pkey" Note this happens while unit testing only - the actual page runs fine in both MySQL & PostGresql. Really having a heckuva time figuring this one out. Anyone have ideas? Below are the Postgresql "\d business_contact" & offending tests.py method if they help. No changes made to either DB except the (same) South migrations Thanks first_name | character varying(200) | not null mobile_phone | character varying(100) | surname | character varying(200) | not null business_id | integer | not null created | timestamp with time zone | not null deleted | boolean | not null default false updated | timestamp with time zone | not null slug | character varying(150) | not null phone | character varying(100) | email | character varying(75) | id | integer | not null default nextval('business_contact_id_seq'::regclass) Indexes: "business_contact_pkey" PRIMARY KEY, btree (id) "business_contact_slug_key" UNIQUE, btree (slug) "business_contact_business_id" btree (business_id) Foreign-key constraints: "business_id_refs_id_772cc1b7b40f4b36" FOREIGN KEY (business_id) REFERENCES business(id) DEFERRABLE INITIALLY DEFERRED Referenced by: TABLE "business" CONSTRAINT "primary_contact_id_refs_id_dfaf59c4041c850" FOREIGN KEY (primary_contact_id) REFERENCES business_contact(id) DEFERRABLE INITIALLY DEFERRED TEST DEF: def test_add_business_contact(self): """ Add a business contact """ contact_slug = 'test-new-contact-added-new-adf' business_id = 1 business = Business.objects.get(id=business_id) postdata = { 'first_name': 'Test', 'surname': 'User', 'business': '1', 'slug': contact_slug, 'email': '[email protected]', 'phone': '12345678', 'mobile_phone': '9823452', 'business': 1, 'business_id': 1, } #Test to ensure contacts that should not exist are not returned contact_not_exists = Contact.objects.filter(slug=contact_slug) self.assertFalse(contact_not_exists) #Add the contact and ensure it is present in the DB afterwards """ contact_add_url = '%s%s/contact/add/' % (settings.BUSINESS_URL, business.slug) self.client.post(contact_add_url, postdata) added_contact = Contact.objects.filter(slug=contact_slug) print added_contact try: self.assertTrue(added_contact) except: formset = ContactForm(postdata) print formset.errors self.assertFalse(True, "Contact not found in the database - most likely, the post values in the test didn't validate against the form")

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  • How to justify using a scripting language as part of a project

    - by sylvanaar
    I have a specific project in which I want to use either a scripting language + C, or as an alternative a 100% Java solution. The program adapts a legacy system for use with other moderns systems. Basically, I have few choices as to what language I can use. I have C/C++, Java 1.4, and I have also compiled the Lua for this environment. The program does 'screen scraping' and has to deal with alot of strings. That part of the code is highly variable. Most of the developers at my company use C, so - my original design was to write some portions in C, and use Lua for the part that dealt with strings and changed freqently. I was told 'You have to justify your use of the scripting language.' So i reworked my design using 100% Java, and was told - Java wont have enough performance. You should do the whole thing in C. I'm not controlling lasers or doing image processing - just some screen scraping. I still have to provide justification for using anything but C - so what justification can I provide?

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  • Problem with writing mobilesubstrate plugins for iOS

    - by overboming
    I am trying to hooking message sending for iOS 3.2, I implement my own hook on a working ExampleHook program I find on the web. But my hook apparently caused segmentation fault everytime it hooks and I don't know why. I want to hook to [NSURL initWithString:(NSString *)URLString relativeToURL:(NSURL *)baseURL; and here is my related implementation static id __$GFWInterceptor_NSURL_initWithString2(NSURL<GFWInterceptor> *_NSURL, NSString *URLString, NSURL* baseURL){ NSLog(@"We have intercepted this url: %@",URLString); [_NSURL __HelloNSURL_initWithString:URLString relativeToURL:baseURL]; establish hook Class _$NSURL = objc_getClass("NSURL"); MSHookMessage(_$NSURL, @selector(initWithString:relativeToURL:), (IMP) &__$GFWInterceptor_NSURL_initWithString2, "__HelloNSURL_"); original method declaration - (void)__HelloNSURL_initWithString:(NSString *)URLString relativeToURL:(NSURL *)baseURL; and here is my gdb backtrace Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x74696e71 0x335625f8 in objc_msgSend () (gdb) bt 0 0x335625f8 in objc_msgSend () 1 0x32c05b1a in CFStringGetLength () 2 0x32c108a8 in _CFStringIsLegalURLString () 3 0x32b1c32a in -[NSURL initWithString:relativeToURL:] () 4 0x000877c0 in __$GFWInterceptor_NSURL_initWithString2 () 5 0x32b1c220 in +[NSURL URLWithString:relativeToURL:] () 6 0x32b1c1f4 in +[NSURL URLWithString:] () 7 0x3061c614 in createUniqueWebDataURL () 8 0x3061c212 in +[WebFrame(WebInternal) _createMainFrameWithSimpleHTMLDocumentWithPage:frameView:withStyle:editable:] () and apparently it hooks, but there is some memory issue there and I can't find anything to blame now

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  • Difference between float and double

    - by VaioIsBorn
    I know, i've read about the difference between double precision and single precision etc. But they should give the same results on most cases right ? I was solving a problem on a programming contest and there were calculations with floating point numbers that were not really big so i decided to use float instead of double, and i checked it - i was getting the correct results. But when i send the solution, it said only 1 of 10 tests was correct. I checked again and again, until i found that using float is not the same using double. I put double for the calculations and double for the output, and the program gave the SAME results, but this time it passed all the 10 tests correctly. I repeat, the output was the SAME, the results were the SAME, but putting float didn't work - only double. The values were not so big too, and the program gave the same results on the same tests both with float and double, but the online judge accepted only the double-provided solution. Why ? What is the difference ?

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  • Closing thread using ExitThread - C

    - by Jamie Keeling
    I have a simple program that creates a thread, loops twenty times and then makes a call to close itself and perform the necessary cleanup. When I debug the program it reaches the ExitThread(); method and pauses, ignoring the printf(); I have set up after it to signal to me it's closed. Is this normal or am I forgetting to do something? I'm new to threading using C. Main() void main() { Time t; int i = 0; StartTimer(); for(i = 0; i < 20; i++) { t = GetTime(); printf("%d.%.3d\n", t.seconds, t.milliseconds); Sleep(100); } StopTimer(); } Thread Creation void StartTimer() { DWORD threadId; seconds = 0; milliseconds = 0; // Create child thread hThread = CreateThread( NULL, // lpThreadAttributes (default) 0, // dwStackSize (default) ThreadFunc, // lpStartAddress NULL, // lpParameter 0, // dwCreationFlags &threadId // lpThreadId (returned by function) ); // Check child thread was created successfully if(hThread == NULL) { printf("Error creating thread\n"); } } Thread Close void StopTimer() { DWORD exitCode; if(GetExitCodeThread(hThread,&exitCode) != 0) { ExitThread(exitCode); printf("Thread closed"); if(CloseHandle(hThread)) { printf("Handle closed"); } } }

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  • How does Amazon's Statistically Improbable Phrases work?

    - by ??iu
    How does something like Statistically Improbable Phrases work? According to amazon: Amazon.com's Statistically Improbable Phrases, or "SIPs", are the most distinctive phrases in the text of books in the Search Inside!™ program. To identify SIPs, our computers scan the text of all books in the Search Inside! program. If they find a phrase that occurs a large number of times in a particular book relative to all Search Inside! books, that phrase is a SIP in that book. SIPs are not necessarily improbable within a particular book, but they are improbable relative to all books in Search Inside!. For example, most SIPs for a book on taxes are tax related. But because we display SIPs in order of their improbability score, the first SIPs will be on tax topics that this book mentions more often than other tax books. For works of fiction, SIPs tend to be distinctive word combinations that often hint at important plot elements. For instance, for Joel's first book, the SIPs are: leaky abstractions, antialiased text, own dog food, bug count, daily builds, bug database, software schedules One interesting complication is that these are phrases of either 2 or 3 words. This makes things a little more interesting because these phrases can overlap with or contain each other.

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  • CIE XYZ colorspace: do I have RGBA or XYZA?

    - by Tronic
    I plan to write a painting program based on linear combinations of xy plane points (0,1), (1,0) and (0,0). Such system works identically to RGB, except that the primaries are not within the gamut but at the corners of a triangle that encloses the entire gamut. I have seen the three points being referred to as X, Y and Z (upper case) somewhere, but I cannot find the page anymore (I marked them to the picture myself). My pixel format stores the intensity of each of those three components the same way as RGB does, together with alpha value. This allows using pretty much any image manipulation operation designed for RGBA without modifying the code. What is my format called? Is it XYZA, RGBA or something else? Google doesn't seem to know of XYZA. RGBA will get confused with sRGB + alpha (which I also need to use in the same program). Notice that the primaries X, Y and Z and their intensities have little to do with the x, y and z coordinates (lower case) that are more commonly used.

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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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  • ASP can't connect to SQL Server database

    - by birdus
    I'm trying to get a classic ASP application to connect to a local SQL Server 2008 database. The app and database were built by someone else. I'm just trying to get them installed and running on my machine (Windows 7). I'm getting the following error when when the ASP app tries to connect to the database: Could not connect to database: Error Number: -2147467259 Error Message: [ConnectionOpen (Connect()).] does not exist or access denied. I don't see any messages in the Windows Event Viewer. I'm looking at: Event Viewer-Windows Logs-Application. It's a fresh database install using a simple restore. The SQL Server install uses the default instance. SQL Server and Windows authentication are both allowed. I left the existing connection string (in the ASP code) in tact and just tried adding that to my SQL Server installation. Here's the connection string: strConn = "PROVIDER=SQLOLEDB;SERVER=localhost;UID=TheUser;PWD=ThePassword;DATABASE=TheDatabase;" To add that user to SQL Server, I went to Security/Logins in SSMS and added the user and the password. I selected the database in question as the Default database. I thought that might do the trick, but it didn't. Then, I went into TheDatabase, then went into Security there. I added a new user there, referencing the new user I had already added in server Security. Under Owned Schemas, I clicked db_owner and under Role Members I checked db_accessadmin and db_owner. None of this gave the ASP application access to the database. The sid values match in sys.database_principals and sys.server_principals for the login in question. I am able to login to SSMS using this login. The app needs to execute selects against the database like this: oConn.Execute('select * from someTable') I'm not a DBA and am sort of grasping at straws here. How do I get this thing connected? Thanks, Jay

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  • Why does the answer print out twice?

    - by rEgonicS
    I made a program that returns the product a*b*c where a,b,c are pythagorean triples and add up to 1000. The program does output the correct answer but does it twice. I was curious as to why this is so.After playing around with it a bit I found out that it prints out when a = 200 b = 375 c = 425. And once again when a = 375 b = 200 c = 425. *How do you put your code into a "code" block? It does it automatically for part of the code but as you can see the top portion and bottom line is left out. bool isPythagTriple(int a, int b, int c); int main() { for(int a = 1; a < 1000; a++) { for(int b = 1; b < 1000; b++) { for(int c = 1; c < 1000; c++) { if( ((a+b+c)==1000) && isPythagTriple(a,b,c) ) { cout << a*b*c << " "; break; } } } } return 0; } bool isPythagTriple(int a, int b, int c) { if( (a*a)+(b*b)-(c*c) == 0 ) return true; else return false; }

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  • How to copy generically superclass instances to subclass instances?

    - by gerry
    Hi @all, I have a class hierarchy / inheritance like this: public class A { private String name; // with getters & setters public void doAWithName(){ ... } } public class B extends A { public void doBWithName(){ // a differnt implementation to what I do in class A } } public class C extends B { public void doCWithName(){ // a differnt implementation to what I do in class A and B } } So at one time there is a instance of class A with the initialized field "name". Later I want this instance of A get wrapped into instance of B or C. So the superclasses should be get wrapped with a subclass! How can I make this most efficent with respect to DRY? I've thought about a constructor that does some copying with the getters/setters. But in this case I have to repeat myself - and this doesn't respect anymore to my initial requirement of DRY! So, how can I warp A to B by just initializing B's new fields (with default values) and delegating the rest to a method in A (which knows more than B about which fields of A should be accessed...). In the same way: If A should be wrapped into C only a method in c should init C's 'new' fields, delegate to B's wrap method (which therefore inits B's 'new' fields in C) and at last B delegates to A which copies it's fields to the fields of C). So in the end I have a new instance of C which has the values of A wrapped (and some default init values to the fields which the inheritance hierarchy has added).

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  • rails not recognizing project

    - by tipu
    I can create a new project using rails and I can use stuff like rails migration ... and i (correctly) get a error because the sqlite gem is missing. but when i try using rails migration ... with a project i checked out from github, it doesn't recognize that it is a rails project i get: Usage: rails new APP_PATH [options] Options: -d, [--database=DATABASE] # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db) # Default: sqlite3 -O, [--skip-active-record] # Skip Active Record files [--dev] # Setup the application with Gemfile pointing to your Rails checkout -J, [--skip-prototype] # Skip Prototype files -T, [--skip-test-unit] # Skip Test::Unit files -G, [--skip-git] # Skip Git ignores and keeps -b, [--builder=BUILDER] # Path to an application builder (can be a filesystem path or URL) [--edge] # Setup the application with Gemfile pointing to Rails repository -m, [--template=TEMPLATE] # Path to an application template (can be a filesystem path or URL) -r, [--ruby=PATH] # Path to the Ruby binary of your choice # Default: /usr/bin/ruby1.8 [--skip-gemfile] # Don't create a Gemfile and it goes on. any ideas? edit: it's probably an important detail that earlier my rails wasn't working at all. i had to cp /usr/bin/ruby to /usr/bin/local/ruby

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  • C ] How can I handle weird errors from calculating acos / sin / atan2?

    - by Phrixus
    Has anyone seen this weird value while handling sin / cos/ tan / acos.. math stuff? ===THE WEIRD VALUE=== -1.#IND00 ===================== void inverse_pos(double x, double y, double& theta_one, double& theta_two) { // Assume that L1 = 350 and L2 = 250 double B = sqrt(x*x + y*y); double angle_beta = atan2(y, x); double angle_alpha = acos((L2*L2 - B*B - L1*L1) / (-2*B*L1)); theta_one = angle_beta + angle_alpha; theta_two = atan2((y-L1*sin(theta_one)), (x-L1*cos(theta_one))); } This is the code I was working on. In a particular condition - like when x & y are 10 & 10, this code stores -1.#IND00 into theta_one & theta_two. It doesn't look like either characters or numbers :( Without a doubt, atan2 / acos / stuff are the problems. But the problem is, try and catch doesn't work either cuz those double variables have successfully stored some values in them. Moreover, the following calculations never complain about it and never break the program! I'm thinking of forcing to use this value somehow and make the entire program crash... So that I can catch this error.. Except for that idea, I have no idea how I should check whether these theta_one and theta_two variables have stored this crazy values. Any good ideas? Thank you in advance..

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  • Modifying C# dictionary value

    - by minjang
    I'm a C++ expert, but not at all for C#. I created a Dictionary<string, STATS>, where STATS is a simple struct. Once I built the dictionary with initial string and STATS pairs, I want to modify the dictionary's STATS value. In C++, it's very clear: Dictionary<string, STATS*> benchmarks; Initialize it... STATS* stats = benchmarks[item.Key]; // Touch stats directly However, I tried like this in C#: Dictionary<string, STATS> benchmarks = new Dictionary<string, STATS>(); // Initialize benchmarks with a bunch of STATS foreach (var item in _data) benchmarks.Add(item.app_name, item); foreach (KeyValuePair<string, STATS> item in benchmarks) { // I want to modify STATS value inside of benchmarks dictionary. STATS stat_item = benchmarks[item.Key]; ParseOutputFile("foo", ref stat_item); // But, not modified in benchmarks... stat_item is just a copy. } This is a really novice problem, but wasn't easy to find an answer. EDIT: I also tried like the following: STATS stat_item = benchmarks[item.Key]; ParseOutputFile(file_name, ref stat_item); benchmarks[item.Key] = stat_item; However, I got the exception since such action invalidates Dictionary: Unhandled Exception: System.InvalidOperationException: Collection was modified; enumeration operation may not execute. at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at System.Collections.Generic.Dictionary`2.Enumerator.MoveNext() at helper.Program.Main(String[] args) in D:\dev\\helper\Program.cs:line 75

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  • A feeling that I'm not that good developer

    - by Karim
    Hi, Im having a strange feeling, but let me first introduce myself as a software developer. I started to program when I was still a kid, I had about 10 or 11 years. I really enjoy my work and never get bored from it. It's amazing how somebody could be paid for what he really likes to do and would be doing it anyway even for free. WHen I first started to program, I was feeling proud of what I was doing, each application I built was for me a success and after 2-3 year I had a feeling that I'm a coding guru. It was a nice feeling ;-) But the more I was in the field, the more types of software I started to develop I was starting to have a feeling that I'm completely wrong in that I'm guru. I felt that I'm not even a mediocre developer. Each new field I start to work on is giving me this feeling. Like when I once developed a device driver for a client, I saw how much I need to learn about device drivers. When I developed a video filter for an application, I saw how much do I still need to learn about DirectShow, Color Spaces, and all the theory behind that. The worst thing was when I started to learn algorithms. It was several years ago. I knew then the basic structures and algorithms like the sorting, some types of trees, some hashtables, strings etc.. and when I really wanted to learn a group of structures I learned about 5-6 new types and saw that in fact even this small group has several hundred subtypes of structures. It's depressing how little time people have in their lives to learn all this stuff. I'm now a software developer with about 10 years of experience and I still feel that I'm not a proficient developer when I think about things that others do in the industry. Is this normal what I'm experiencing or is it a sign of a destructive excessive ambition? Thanks in advance for any comments.

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  • Combinationally unique MySQL tables

    - by Jack Webb-Heller
    So, here's the problem (it's probably an easy one :P) This is my table structure: CREATE TABLE `users_awards` ( `user_id` int(11) NOT NULL, `award_id` int(11) NOT NULL, `duplicate` int(11) NOT NULL DEFAULT '0', UNIQUE KEY `award_id` (`award_id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 So it's for a user awards system. I don't want my users to be granted the same award multiple times, which is why I have a 'duplicate' field. The query I'm trying is this (with sample data of 3 and 2) : INSERT INTO users_awards (user_id, award_id) VALUES ('3','2') ON DUPLICATE KEY UPDATE duplicate=duplicate+1 So my MySQL is a little rusty, but I set user_id to be a primary key, and award_id to be a UNIQUE key. This (kind of) created the desired effect. When user 1 was given award 2, it entered. If he/she got this twice, only one row would be in the table, and duplicate would be set to 1. And again, 2, etc. When user 2 was given award 1, it entered. If he/she got this twice, duplicate updated, etc. etc. But when user 1 is given award 1 (after user 2 has already been awarded it), user 2 (with award 1)'s duplicate field increases and nothing is added to user 1. Sorry if that's a little n00bish. Really appreciate the help! Jack

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  • Issue reading in a cell from Excel with Apache POI

    - by Nick
    I am trying to use Apache POI to read in old (pre-2007 and XLS) Excel files. My program goes to the end of the rows and iterates back up until it finds something that's not either null or empty. Then it iterates back up a few times and grabs those cells. This program works just fine reading in XLSX and XLS files made in Office 2010. I get the following error message: Exception in thread "main" java.lang.NumberFormatException: empty String at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source) at java.lang.Double.parseDouble(Unknown Source) at the line: num = Double.parseDouble(str); from the code: str = cell.toString(); if (str != "" || str != null) { System.out.println("Cell is a string"); num = Double.parseDouble(str); } else { System.out.println("Cell is numeric."); num = cell.getNumericCellValue(); } where the cell is the last cell in the document that's not empty or null. When I try to print the first cell that's not empty or null, it prints nothing, so I think I'm not accessing it correctly.

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  • Unresolved external symbol error in c++

    - by Crystal
    I am trying to do a simple hw problem involving namespace, static data members and functions. I am getting an unresolved external symbol error Error 1 error LNK2001: unresolved external symbol "private: static double JWong::SavingsAccount::annualInterestRate" (?annualInterestRate@SavingsAccount@JWong@@0NA) SavingsAccount.obj SavingsAccount And I don't see why I am getting this error. Maybe I don't know something about static variables compared to regular data members that is causing this error. Here is my code: SavingsAccount.h file #ifndef JWONG_SAVINGSACCOUNT_H #define JWONG_SAVINGSACCOUNT_H namespace JWong { class SavingsAccount { public: // default constructor SavingsAccount(); // constructor SavingsAccount(double savingsBalance); double getSavingsBalance(); void setSavingsBalance(double savingsBalance); double calculateMonthlyInterest(); // static functions static void modifyInterestRate(double newInterestRate); static double getAnnualInterestRest(); private: double savingsBalance; // static members static double annualInterestRate; }; } #endif SavingsAccount.cpp file #include <iostream> #include "SavingsAccount.h" // default constructor, set savingsBalance to 0 JWong::SavingsAccount::SavingsAccount() : savingsBalance(0) {} // constructor JWong::SavingsAccount::SavingsAccount(double savingsBalance) : savingsBalance(savingsBalance) {} double JWong::SavingsAccount::getSavingsBalance() { return savingsBalance; } void JWong::SavingsAccount::setSavingsBalance(double savingsBalance) { this->savingsBalance = savingsBalance; } // returns monthly interest and sets savingsBalance to new amount double JWong::SavingsAccount::calculateMonthlyInterest() { double monthlyInterest = savingsBalance * SavingsAccount::annualInterestRate / 12; setSavingsBalance(savingsBalance + monthlyInterest); return monthlyInterest; } void JWong::SavingsAccount::modifyInterestRate(double newInterestRate) { SavingsAccount::annualInterestRate = newInterestRate; } double JWong::SavingsAccount::getAnnualInterestRest() { return SavingsAccount::annualInterestRate; }

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  • how to Solve the "Digg" problem in MongoDB

    - by user193116
    A while back,a Digg developer had posted this blog ,"http://about.digg.com/blog/looking-future-cassandra", where the he described one of the issues that were not optimally solved in MySQL. This was cited as one of the reasons for their move to Cassandra. I have been playing with MongoDB and I would like to understand how to implement the MongoDB collections for this problem From the article, the schema for this information in MySQL : CREATE TABLE Diggs ( id INT(11), itemid INT(11), userid INT(11), digdate DATETIME, PRIMARY KEY (id), KEY user (userid), KEY item (itemid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE Friends ( id INT(10) AUTO_INCREMENT, userid INT(10), username VARCHAR(15), friendid INT(10), friendname VARCHAR(15), mutual TINYINT(1), date_created DATETIME, PRIMARY KEY (id), UNIQUE KEY Friend_unique (userid,friendid), KEY Friend_friend (friendid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; This problem is ubiquitous in social networking scenario implementation. People befriend a lot of people and they in turn digg a lot of things. Quickly showing a user what his/her friends are up to is very critical. I understand that several blogs have since then provided a pure RDBMs solution with indexes for this issue; however I am curious as to how this could be solved in MongoDB.

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  • Word forms with too many ActiveX checkboxes load slowly.

    - by Luke
    Hi there, my company's software product has a feature that allows users to generate forms from Word templates. The program auto fills some fields from the SQL database and the user can fill in other data that they desire. So we have a .dotx template that holds the design of the form, and then the user gets the .docx file to fill out when they call it from our program. The problem we're having is that some of our users have been finding that the forms take an exceptionally long time to open up and then, once open, are so slow to respond (scroll around, etc) that they're unusable. So in my investigations so far, I've found out that the problem systems are one with lower powered CPUs (unfortunately it happens for systems above our system requirements) and the Word forms that cause the problems are ones with large amount of ActiveX style checkboxes on them. I verified that reducing the ActiveX checkboxes fixes the form loading problems. So I have the following questions about solutions (we're using Word 2007): 1) Is there any way to configure Word, or some other settings, so that there won't be such a strain opening a Word form with lots of ActiveX checkboxes? Any way of speeding up Word's opening? 2) Using Legacy style checkboxes instead of the ActiveX ones makes the forms load fine, but it looks like the user has to double-click the checkbox and change Default Value-Checked. Is there a way to configure it so that they can simply click on the checkbox to tick it? "Legacy Forms" checkbox as a name kind of worries me (Legacy…), does that mean a future version of word at some point wouldn't load the checkboxes because they're "legacy"? 3) Yes, it became clear to me after a little bit of research into solutions that Word is not the tool for the job for forms like I'm describing. InfoPath seems to be exactly what we should have been using all along but unfortunately I wasn't involved in the decision making or development of these forms, just tasked with coming up with a solution. I'd appreciate answers to any of these, or if anyone has any other ideas for solutions to this problem. Thanks

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  • How to check for mip-map availability in OpenGL?

    - by Xavier Ho
    Recently I bumped into a problem where my OpenGL program would not render textures correctly on a 2-year-old Lenovo laptop with an nVidia Quadro 140 card. It runs OpenGL 2.1.2, and GLSL 1.20, but when I turned on mip-mapping, the whole screen is black, with no warnings or errors. This is my texture filter code: glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE); After 40 minutes of fiddling around, I found out mip-mapping was the problem. Turning it off fixed it: // glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE); I get a lot of aliasing, but at least the program is visible and runs fine. Finally, two questions: What's the best or standard way to check if mip-mapping is available on a machine, aside from checking OpenGL versions? If mip-mapping is not available, what's the best work-around to avoid aliasing?

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  • WPF - How do I use the UserControl with a dependency property and view model?

    - by user320849
    Hello, My goal is to have a user select a year and a month. Translate the selection into a date and have the user control send the date back to my view model. That part works for me....However, I cannot get the ViewModel's initial date to set those drop downs. public static readonly DependencyProperty Date = DependencyProperty.Register("ReturnDate", typeof(DateTime), typeof(DatePicker), new FrameworkPropertyMetadata{BindsTwoWayByDefault = true,}); public DateTime ReturnDate { get { return Convert.ToDateTime(GetValue(Date)); } set { SetDropDowns(value); SetValue(Date, value); } } The SetDropDowns(value) just sets the selected items on the combo boxes, however, the program never makes it to that method. On the view I am using: <cc1:DatePicker ReturnDate="{Binding Path=StartDate, Mode=TwoWay}" IsStart="True" /> If this has been answered, then my bad. I looked around and didn't see anything that worked for me. Thus, when the program loads how do I get the value from the view model to a method in order to set the combo boxes? Thanks, -Scott

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