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• What's the right Java generic for a collection of elements with unique addressable indices?

  - by Rocreex

  I'm on my way to programming a database application and in our course we are told to implement a library of elements using one of the Java Collections. Each of the elements has a unique ID with which it's supposed to be addressed. Now I am wondering how this can be done. I though about using a ListArray but this won't work because the only way of addressing List elements is through the index which you can't control. Do you have some advice for me?

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• How to get the userID from a custom ASP.Net Membership Provider w/ non-unique usernames?

  - by Aplato

  I've created a custom asp.net membership provider that authenticates against a legacy database. The problem I'm running into to is how to handle users that have same username. I've repeatedly tried convincing my boss that a username should be unique but this has been to no avail.

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• How Can I Generate Random Unqiue Numbers in C#

  - by peace

  public int GenPurchaseOrderNum() { Random random = new Random(); _uniqueNum = random.Next(13287, 21439); return UniqueNum; } I removed unique constraint from the PONumber column in the db because an employee should only generate P.O. # when the deal is set. Otherwise, P.O. # would have 0. P.O. Number used to have unique constraint, this forces employee to generate P.O. in all cases so the db doesn't throw unique constraint error. Since i removed the unique constraint, any quote doesn't have P.O. will carry 0 value. Otherwise, a unique value is generated for P.O. #. However, i don't have a unique constraint in db which makes it hard for me to know whether the application generated P.O. # is unique or not. What should i do? I hope my question is clear enough

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• Database indexes - what should they be

  - by WebweaverD

  Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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• problem when trying to empty a stack in c

  - by frx08

  Hi all, (probably it's a stupid thing but) I have a problem with a stack implementation in C language, when I try to empty it, the function to empty the stack does an infinite loop.. the top of the stack is never null. where I commit an error? thanks bye! #include <stdio.h> #include <stdlib.h> typedef struct stack{ size_t a; struct stack *next; } stackPos; typedef stackPos *ptr; void push(ptr *top, size_t a){ ptr temp; temp = malloc(sizeof(stackPos)); temp->a = a; temp->next = *top; *top = temp; } void freeStack(ptr *top){ ptr temp = *top; while(*top!=NULL){ //the program does an infinite loop *top = temp->next; free(temp); } } int main(){ ptr top = NULL; push(&top, 4); push(&top, 8); //down here the problem freeStack(&top); return 0; }

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• OpenGL Calls Lock/Freeze

  - by Necrolis

  I am using some dell workstations(running WinXP Pro SP 2 & DeepFreeze) for development, but something was recenlty loaded onto these machines that prevents any opengl call(the call locks) from completing(and I know the code works as I have tested it on 'clean' machines, I also tested with simple opengl apps generated by dev-cpp, which will also lock on the dell machines). I have tried to debug my own apps to see where exactly the gl calls freeze, but there is some global system hook on ZwQueryInformationProcess that messes up calls to ZwQueryInformationThread(used by ExitThread), preventing me from debugging at all(it causes the debugger, OllyDBG, to go into an access violation reporting loop or the program to crash if the exception is passed along). the hook: ntdll.ZwQueryInformationProcess 7C90D7E0 B8 9A000000 MOV EAX,9A 7C90D7E5 BA 0003FE7F MOV EDX,7FFE0300 7C90D7EA FF12 CALL DWORD PTR DS:[EDX] 7C90D7EC - E9 0F28448D JMP 09D50000 7C90D7F1 9B WAIT 7C90D7F2 0000 ADD BYTE PTR DS:[EAX],AL 7C90D7F4 00BA 0003FE7F ADD BYTE PTR DS:[EDX+7FFE0300],BH 7C90D7FA FF12 CALL DWORD PTR DS:[EDX] 7C90D7FC C2 1400 RETN 14 7C90D7FF 90 NOP ntdll.ZwQueryInformationToken 7C90D800 B8 9C000000 MOV EAX,9C the messed up function + call: ntdll.ZwQueryInformationThread 7C90D7F0 8D9B 000000BA LEA EBX,DWORD PTR DS:[EBX+BA000000] 7C90D7F6 0003 ADD BYTE PTR DS:[EBX],AL 7C90D7F8 FE ??? ; Unknown command 7C90D7F9 7F FF JG SHORT ntdll.7C90D7FA 7C90D7FB 12C2 ADC AL,DL 7C90D7FD 14 00 ADC AL,0 7C90D7FF 90 NOP ntdll.ZwQueryInformationToken 7C90D800 B8 9C000000 MOV EAX,9C So firstly, anyone know what if anything would lead to OpenGL calls cause an infinite lock,and if there are any ways around it? and what would be creating such a hook in kernal memory ? Update: After some more fiddling, I have discovered a few more kernal hooks, a lot of them are used to nullify data returned by system information calls(such as the remote debugging port), I also managed to find out the what ever is doing this is using madchook.dll(by madshi) to do this, this dll is also injected into every running process(these seem to be some anti debugging code). Also, on the OpenGL side, it seems Direct X is fine/unaffected(I ran one of the DX 9 demo's without problems), so could one of these kernal hooks somehow affect OpenGL?

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• Is the following C code safe?

  - by lali

  #include<cstdio> #include<stdlib.h> int main() { char* ptr=NULL; printf("%s",ptr); return 0; } It prints (null) as output. The above is a sample code. In real code i get char* as a return of a function and i wish to print the character string for logging. However, NULL is also a valid return value of that function and so i am wondering if a null check is required before printing the character string? char* ptr=someFuncion(); // do i need the following if statement? if(ptr!=NULL) { printf("%s",ptr); } I just want to be sure that the output would be same i.e if ptr=NULL then output should be (null) on all platforms and compilers and the above code(without if statement) would not crash on any C standard compatible platform. In short, is the above code(without the if statement) standard compatible? Thanks for your help and patience :) Regards lali

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• how to write binary copy of structure array to file

  - by cerr

  I would like to write a binary image of a structure array to a binary file. I have tried this so far: #include <stdio.h> #include <string.h> #define NUM 256 const char *fname="binary.bin"; typedef struct foo_s { int intA; int intB; char string[20]; }foo_t; void main (void) { foo_t bar[NUM]; bar[0].intA = 10; bar[0].intB = 999; strcpy(bar[0].string,"Hello World!"); Save(bar); printf("%s written succesfully!\n",fname); } int Save(foo_t* pData) { FILE *pFile; int ptr = 0; int itr = 0; pFile = fopen(fname, "w"); if (pFile == NULL) { printf("couldn't open %s\n", fname); return; } for (itr = 0; itr<NUM; itr++) { for (ptr=0; ptr<sizeof(foo_t); ptr++) { fputc((unsigned char)*((&pData[itr])+ptr), pFile); } fclose(pFile); } } but the compiler is saying aggregate value used where an integer was expected fputc((unsigned char)*((&pData[itr])+ptr), pFile); and I don't quite understand why, what am I doing wrong? Thanks!

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• why no implicit conversion from pointer to reference to const pointer.

  - by user316606

  I'll illustrate my question with code: #include <iostream> void PrintInt(const unsigned char*& ptr) { int data = 0; ::memcpy(&data, ptr, sizeof(data)); // advance the pointer reference. ptr += sizeof(data); std::cout << std::hex << data << " " << std::endl; } int main(int, char**) { unsigned char buffer[] = { 0x11, 0x11, 0x11, 0x11, 0x22, 0x22, 0x22, 0x22, }; /* const */ unsigned char* ptr = buffer; PrintInt(ptr); // error C2664: ... PrintInt(ptr); // error C2664: ... return 0; } When I run this code (in VS2008) I get this: error C2664: 'PrintInt' : cannot convert parameter 1 from 'unsigned char *' to 'const unsigned char *&'. If I uncomment the "const" comment it works fine. However shouldn't pointer implicitly convert into const pointer and then reference be taken? Am I wrong in expecting this to work? Thanks!

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• How to generate a unique hash for a URL ?

  - by Jacques René Mesrine

  Given these two images from twitter. http://a3.twimg.com/profile_images/130500759/lowres_profilepic.jpg http://a1.twimg.com/profile_images/58079916/lowres_profilepic.jpg I want to download them to local filesystem & store them in a single directory. How shall I overcome name conflicts ? In the example above, I cannot store them as *lowres_profilepic.jpg*. My design idea is treat the URLs as opaque strings except for the last segment. What algorithms (implemented as f) can I use to hash the prefixes into unique strings. f( "http://a3.twimg.com/profile_images/130500759/" ) = 6tgjsdjfjdhgf f( "http://a1.twimg.com/profile_images/58079916/" ) = iuhd87ysdfhdk That way, I can save the files as:- 6tgjsdjfjdhgf_lowres_profilepic.jpg iuhd87ysdfhdk_lowres_profilepic.jpg I don't want a cryptographic algorithm as it this needs to be a performant operation.

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• How to use map/reduce to handle more than 10000 unique keys for grouping in MongoDB?

  - by Magnus Johansson

  I am using MongoDB v1.4 and the mongodb-csharp driver and I try to group on a data store that has more than 10000 keys, so I get this error: assertion: group() can't handle more than 10000 unique keys using c# code like this: Document query = new Document().Append("group", new Document() .Append("key", new Document().Append("myfieldname", true)) .Append("$reduce", new CodeWScope( "function(obj,prev) { prev.count++; }")) .Append("initial", new Document().Append("count", 0)) .Append("ns", "myitems")); I read that I should use map/reduce, but I can't figure out how. Can somebody please shed some light on how to use map/reduce? Or is there any other way to get around this limitation? Thanks.

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• Is it possible to bundle a unique file for each copy of iPhone app downloaded from App Store?

  - by futureelite7

  Hi, I would like to verify the identity of each instance of the iPhone application that a user might use to connect to my service. To that end, I would like each instance of the iPhone app downloaded to include a certificate that I generate, or even some sort of UUID that I have generated. Does the App Store support the inclusion of unique files in an app bundle? Or, must such identifiers be downloaded only after the app is installed? If that is the case, is there a mechanism to ensure that the app downloaded is trusted (from me), instead of from an impersonator?

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• Java generics: What is the compiler's issue here? ("no unique maximal instance")

  - by Epaga

  I have the following methods: public <T> T fromJson( Reader jsonData, Class<T> clazz ) { return fromJson( jsonData, (Type)clazz ); } public <T> T fromJson( Reader jsonData, Type clazz ) { ... } The compiler is saying about the first method: type parameters of <T>T cannot be determined; no unique maximal instance exists for type variable T with upper bounds T,java.lang.Object return fromJson( jsonData, (Type)clazz ); ^ What is the problem?

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• Rails, How can I combine multiple model attributes to create a unique permalink using permalink_fu?

  - by Ranknoodle

  Can Permalink_fu combine 2 or more model attributes to create a unique permalink? Let's say I have a Business Model, this model contains :name, :address, :phone, :city, :state, :country etc. attributes. Right now I have permalink set up in this model only for :name has_permalink :name So I would get "/biz/name". However I would like to combine the Business name, city, and a incremental number if there are more than 1 location in the city for that business. For example I would like to use: "/biz/joes-coffee-shack-chicago" for the permalink or if a multple location business "/biz/starbucks-chicago-92" Is this possible with the current permalink_fu plugin or some fork of permalink_fu? Or will this require some modification to the permalink_fu plugin?

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• Easiest way of checking if a string consists of unique characters?

  - by serg555

  I need to check in Java if a word consists of unique letters (case insensitive). As straight solution is boring, I came up with: For every char in a string check if indexOf(char) == lastIndexOf(char). Add all chars to HashSet and check if set size == string length. Convert a string to a char array, sort it alphabetically, loop through array elements and check if c[i] == c[i+1]. Currently I like #2 the most, seems like the easiest way. Any other interesting solutions?

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• How do i create a view that can filter unique titles from a checkbox?

  - by buws

  I'm currently creating a view in Drupal that contains a number of fields. What I want to do is to create an exposed filter that is able to filter duplicate titles. The filter would be a checkbox. This is an example of the list NAME TIME RACE DISTANCE John Doe 2.07.54 Boston Marathon 42km Jane Boss 2.15.21 Boston Marathon 42km John Doe 2.02.22 Boston Marathon 42km Jane Boss 2.15.44 Boston Marathon 42km What I want to have is an exposed filter that only shows one unique NAME and sorts it by its best time. The resulting list would look as follows: NAME TIME RACE DISTANCE Jane Boss 2.15.21 Boston Marathon 42km John Doe 2.02.22 Boston Marathon 42km Any help is appreciated!

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• How to get unique URL identifier after inserting item in Google Base with Zend Gdata API?

  - by msumme

  I need to get the unique URL identifier for the product that is created after inserting an item into Google Base using the Zend_Gdata_Gbase library. I can't seem to do this. I am finding a startling lack of documentation online about manipulating the objects used in these applications. The url that I add to the object does not work to retrieve the base item later, which is why I need to get the one that google generates upon submission. I am writing a program that will need to be able to delete content at a later date, and thus will need to store that information in order to keep the website synced with the Google Base feed. Thanks in advance for any help.

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• is a mysql temporary table unique for each user accessing the script that creates it...?

  - by SpikETidE

  Hi everyone... While looking for a way to temporarily save the search results when a user searches for a hotel free between particular dates i came across temporary tables. But certain questions are not answered even in mysql manual.... like... Will the temporary table be unique for each user that executes the script...? Or will it be overwritten when two different users run the script at the same time...? When will the table be destroyed..? When the user closes the browser window or just navigates away from the page in which the script runs...? Thanks for your clarifications...

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• Netlogo behaviorspace, How to export each experiment's plot in a separate directory with a unique name? (Answer is by using pathdir extension)

  - by Marzy

  I have a save-plots function which I call it in my final command of behavior space to export selected plots, I could create unique names for plots so they don't replace each other, for example my output file name for one of the plots is like this: DeathRates, PS true, HCHA false 100,true.csv Let FileNameDeathRates ( word "D: /Results/" "DeathRates, " "PS "PS? ", HCHA " HCHA? MPS "," CV? ".csv" ) So far is good, but I want is to have a directory with name of the experiment and export all plots of that experiment in that directory for example: Let DirName( word "D:/Results/" "PS "PS? ", HCHA " HCHA? MPS "," CV? ) Netlogo already exports plots with proper name and I just want the directory name to be different , and of course prior to the experiment the directory does not exist so the directory should be created first , I could not find a command to create a directory in netlogo without pathdir extension. Any idea on how can I do this? Thanks in advance ;)

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• [PHP] md5(uniqid) makes sense for random unique tokens?

  - by Exception e

  I want to create a token generator that generates tokens that cannot be guessed by the user and that are still unique (to be used for password resets and confirmation codes). I often see this code; does it make sense? md5(uniqid(rand(), true)); According to a comment uniqid($prefix, $moreEntopy = true) yields first 8 hex chars = Unixtime, last 5 hex chars = microseconds. I don't know how the $prefix-parameter is handled.. So if you don't set the $moreEntopy flag to true, it gives a predictable outcome. QUESTION: But if we use uniqid with $moreEntopy, what does hashing it with md5 buy us? Is it better than: md5(mt_rand())

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• Where to find a unique session ID at design time in .Net WinForms.

  - by Jules

  I've created a custom clipboard because it's not possible to make my whole class map serializable - which is a requirement for the windows clipboard. However, I need to distinguish between users who are using my clipboard through a unique id. Basically, I want to be able identify a person who is sat at one PC with one or more copies of visual studio (or similar) open. How do I do that? ps: This is at design-time. pps: It's not critical that it should work between copies of visual studio. One copy would be fine, or even one design surface.

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• Python - Flatten a dict of lists into unique values?

  - by Jonathan Vanasco

  I have a dict of lists in python: content = {88962: [80, 130], 87484: [64], 53662: [58,80]} I want to turn it into a list of the unique values [58,64,80,130] I wrote a manual solution, but it's a manual solution. I know there are more concise and more elegant way to do this with list comprehensions, map/reduce , itertools , etc. anyone have a clue ? content = {88962: [80, 130], 87484: [64], 53662: [58,80]} result = set({}) for k in content.keys() : for i in content[k]: result.add(i) # and list/sort/print just to compare the output r2 = list( result ) r2.sort() print r2

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• Prevent duplicate rows with all non-unique columns (only with MySQL)?

  - by letseatfood

  Ho do I prevent a duplicate row from being created in a table with two columns, neither of which are unique? And can this be done using MySQL only, or does it require checks with my PHP script? Here is the CREATE query for the table in question (two other tables exist, users and roles): CREATE TABLE users_roles ( user_id INT(100) NOT NULL, role_id INT(100) NOT NULL, FOREIGN KEY (user_id) REFERENCES users(user_id), FOREIGN KEY (role_id) REFERENCES roles(role_id) ) ENGINE = INNODB; I would like the following query, if executed more than once, to throw an error: INSERT INTO users_roles (user_id, role_id) VALUES (1, 2); Please do not recommend bitmasks as an answer. Thanks!

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• rails 3, active record: any way to tell how many unique values match a "x LIKE ?" query

  - by jpwynn

  I have a query to find all the phone numbers that match a partial expression such as "ends with 234" @matchingphones = Calls.find :all, :conditions => [ "(thephonenumber LIKE ?)", "%234"] The same phone number might be in the database several times, and so might be returned multiple times by this query if it matches. What I need is to know is UNIQUE phone numbers the query returns. For example if the database contains 000-111-1234 * 000-111-3333 000-111-2234 * 000-111-1234 * 000-111-4444 the existing query will return the 3 records marked with * (eg returns one phone number -1234 twice since it's in the database twice) what I need is a query that returns just once instance of each match, in this case 000-111-1234 * 000-111-2234 *

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• Was: Not unique table :: Now: #1054 - Unknown column - can't understand why!?

  - by Andy Barlow

  Hi! I'm trying to join some tables together in MySQL, but I seem to get an error saying: #1066 - Not unique table/alias: 'calendar_jobs' I really want it to select everything from the cal_events, the 2 user bits and just the destination col from the jobs table, but become "null" if there arn't any job. A right join seemed to fit the bill but doesn't work! Can anyone help!? UPDATE: Thanks for the help on the previous query, I'm now up to this: SELECT calendar_events.* , calendar_users.doctorOrNurse, calendar_users.passportName, calendar_jobs.destination FROM `calendar_events` , `calendar_users` RIGHT JOIN calendar_jobs ON calendar_events.jobID = calendar_jobs.jobID WHERE `start` >= 0 AND calendar_users.userID = calendar_events.userID; But am now getting an error saying: #1054 - Unknown column 'calendar_events.jobID' in 'on clause' What is it this time!? Thanks again!

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