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Manually extracting portions of strings contained in a list (parsing)

- by user1652011

I'm aware that there are modules that fully simplify this function, but saying that I am running from a base install of python (standard modules only), how would I extract the following: I have a list. This list is the contents, line by line, of a webpage. Here is a mock up list (unformatted) for informative purposes: <script> link = "/scripts/playlists/1/" + a.id + "/0-5417069212.asx"; <script> "<a href="/apps/audio/?feedId=11065"><span class="px13">Eastern Metro Area Fire</span>" From the above string, I need the following extracted. The feedId (11065), which is incidentally a.id in the code above., "/scripts/playlists/1/" and "/0-5417069212.asx". Remembering that each of these lines is just contents from objects in a list, how would I go about extracting that data? Here is the full list: contents = urllib2.urlopen("http://www.radioreference.com/apps/audio/?ctid=5586") Pseudo: from urllib2 import urlopen as getpage page_contents = getpage("http://www.radioreference.com/apps/audio/?ctid=5586") feedID = % in (page_contents.search() for "/apps/audio/?feedId=%") titleID = % in (page_contents.search() for "<span class="px13">%</span>") playlistID = % in (page_contents.search() for "link = "%" + a.id + "*.asx";") asxID = * in (page_contents.search() for "link = "*" + a.id + "%.asx";") streamURL = "http://www.radioreference.com/" + playlistID + feedID + asxID + ".asx" I plan to format it as such that streamURL should = : http://www.radioreference.com/scripts/playlists/1/11065/0-5417067072.asx

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List all foreign key constraints that refer to a particular column in a specific table

- by Sid

I would like to see a list of all the tables and columns that refer (either directly or indirectly) a specific column in the 'main' table via a foreign key constraint that has the ON DELETE=CASCADE setting missing. The tricky part is that there would be an indirect relationships buried across up to 5 levels deep. (example: ... great-grandchild- FK3 = grandchild = FK2 = child = FK1 = main table). We need to dig up the leaf tables-columns, not just the very 1st level. The 'good' part about this is that execution speed isn't of concern, it'll be run on a backup copy of the production db to fix any relational issues for the future. I did SELECT * FROM sys.foreign_keys but that gives me the name of the constraint - not the names of the child-parent tables and the columns in the relationship (the juicy bits). Plus the previous designer used short, non-descriptive/random names for the FK constraints, unlike our practice below The way we're adding constraints into SQL Server: ALTER TABLE [dbo].[UserEmailPrefs] WITH CHECK ADD CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] FOREIGN KEY([UserId]) REFERENCES [dbo].[UserMasterTable] ([UserId]) ON DELETE CASCADE GO ALTER TABLE [dbo].[UserEmailPrefs] CHECK CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] GO The comments in this SO question inpire this question.

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Shell script for generating HTML out put

- by user1638016

The following script is generating the desired out put but not redirecting the result to /home/myuser/slavedelay.html #!/bin/bash host=<ip> echo $host user=usr1 password=mypass threshold=300 statusok=OK statuscritical=CRITICAL for i in ert7 ert9 do echo "<html>" > /home/myuser/slavedelay.html if [ "$i" == "ert7" ]; then slvdelay=`mysql -u$user -p$password -h<ip> -S /backup/mysql/mysql.sock -e 'show slave status\G' | grep Seconds_Behind_Master | sed -e 's/ *Seconds_Behind_Master: //'` if [ $slvdelay -ge $threshold ]; then echo "<tr><td>$i</td><td>CRITICAL</td>" >> /home/myuser/slavedelay.html echo "<tr><td>$i</td><td>CRITICAL</td>" else echo "<tr><td>$i</td><td>OK</td>" >> /home/myuser/slavedelay.html echo "<tr><td>$i</td><td>OK</td>" fi fi done echo "</html>" >> /home/myuser/slavedelay.html If I cat the output file /home/myuser/slavedelay.html it gives. <html> </html> Execution result : sh slave_delay.sh <tr><td>sdb7</td><td>OK</td>

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What are the first steps in C#/.NET development?

- by paxdiablo

Okay, I'm biting the bullet and deciding to get into the whole Microsoft/C#/.NET culture and I'm going to do this by putting together a simple (hah!) application. It will basically be an application in which I want to store images and associate with them other optional things. It must be able to import images from the filesystem (and hopefully camera/scanner) then allow the user to add text, audio and other information. I plan to store the images and auxillary information into a database. What the application will do with said data isn't important (yet). Keep in mind I know absolutely nothing about C# or .NET although, as an old codger, I know a great deal about many other things and will regale you with stories and anecdotes until you quietly slip away :-) What are the first steps to take in developing such an application? I've already set out UI layouts and likely process flows although it may be that the development environment dictates changes. Development environment is currently XP SP3 + VS2008 (though I can upgrade if absolutely necessary). What should I be looking at as the first step? Are there any gotchas I should be looking out for?

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java.lang.IllegalStateException: The content of the adapter has changed but ListView.... inspite of calling notifydatasetchanged()

- by Mistaken

What are the best practices to be followed to update the contents of a listactivty by a background thread (Async Task) ? 1) Am calling the notifyDataSetChanged() to update the adapter as soon as i manipulate the contents of the adapter but still my app force closes while the user scrolls or click on the list. Any pointers to prevent this would be very helpfull. Logcat: java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. 2) Where exaclty should i update contents of the listactivity ? inside the doInBackground() or onProgressUpdate()? 3) Am experiencing regular crashes when the user clicks the list item. So will disabling click events on the listactivty during the background operation solve the problem ? If so am not sure how to remove or set item click listeners dynamically to the listactivity. Please instruct me on the too. 4) I dont think blocking all ui interactions during the background async task execution is the only way to solve the problem. I know there is a simple way of doing this but need some help. Thanks in advance. This is my onCreate... protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fa); tvStatus=(TextView) findViewById(R.id.tvStatus); adapter = new SimpleAdapter( this, mostPopularList, R.layout.list_item, new String[] {"title","author","views","date"}, new int[] {R.id.textView1,R.id.textView2,R.id.textView4,R.id.textView3}); //populateList(); setListAdapter(adapter); } My async task... private class LongOperation extends AsyncTask<String, Void, String> { @Override protected String doInBackground(String... params) { // code for adding new listactivty items } @Override protected void onPostExecute(String networkStatus) { adapter.notifyDataSetChanged(); } @Override protected void onPreExecute() { } @Override protected void onProgressUpdate(Void... values) { } }

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Labview + National Instruments hardware or ???

- by NSL

I'm in the processes of buying a new data acquisition system for my company to use for various projects. At first, it's primary purpose will be to monitor up to 20 thermocouples and control the temperature of a composites oven. However, I also plan on using it to monitor accelerometers, strain gauges, and to act as a signal generator. I probably won't be the only one to use it, but I have a good bit of programming experience with Atmel microcontrollers (C). I've used Labview before, but ~5 years ago. Labview would be good because it is easy to pick up on for both me and my coworkers. On the flip side, it's expensive. Right now I have a NI CompactDAQ system with 2 voltage and one thermocouple cards + Labview speced out and it's going to cost $5779! I'm going to try to get the same I/O capabilities with different NI hardware for less $ + labview to see if I can get it for less $. I'd like to see if anyone has any suggestions other than Labview for me. Thanks in advance!

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How to speed-up a simple method (preferably without changing interfaces or data structures)?

- by baol

I have some data structures: all_unordered_m is a big vector containing all the strings I need (all different) ordered_m is a small vector containing the indexes of a subset of the strings (all different) in the former vector position_m maps the indexes of objects from the first vector to their position in the second one. The string_after(index, reverse) method returns the string referenced by ordered_m after all_unordered_m[index]. ordered_m is considered circular, and is explored in natural or reverse order depending on the second parameter. The code is something like the following: struct ordered_subset { // [...] std::vector<std::string>& all_unordered_m; // size = n >> 1 std::vector<size_t> ordered_m; // size << n std::tr1::unordered_map<size_t, size_t> position_m; const std::string& string_after(size_t index, bool reverse) const { size_t pos = position_m.find(index)->second; if(reverse) pos = (pos == 0 ? orderd_m.size() - 1 : pos - 1); else pos = (pos == ordered.size() - 1 ? 0 : pos + 1); return all_unordered_m[ordered_m[pos]]; } }; Given that: I do need all of the data-structures for other purposes; I cannot change them because I need to access the strings: by their id in the all_unordered_m; by their index inside the various ordered_m; I need to know the position of a string (identified by it's position in the first vector) inside ordered_m vector; I cannot change the string_after interface without changing most of the program. How can I speed up the string_after method that is called billions of times and is eating up about 10% of the execution time?

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Using Threads to Handle Sockets

- by user340468

I am working on a java program that is essentially a chat room. This is an assignment for class so no code please, I am just having some issues determining the most feasible way to handle what I need to do. I have a server program already setup for a single client using threads to get the data input stream and a thread to handle sending on the data output stream. What I need to do now is create a new thread for each incoming request. My thought is to create a linked list to contain either the client sockets, or possibly the thread. Where I am stumbling is figuring out how to handle sending the messages out to all the clients. If I have a thread for each incoming message how can I then turn around and send that out to each client socket. I'm thinking that if I had a linkedlist of the clientsockets I could then traverse the list and send it out to each one, but then I would have to create a dataoutputstream each time. Could I create a linkedlist of dataoutputstreams? Sorry if it sounds like I'm rambling but I don't want to just start coding this, it could get messy without a good plan. Thanks!

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Is there an efficient algorithm to distribute resources in a way that both avoids conflict and allows bias?

- by Steve V.

Background (Skip this if you only care about the algorithm) At the university where I work, one of the biggest hassles in our department is classroom scheduling. For illustration purposes and to lay out the scope of the problem, here's how we do scheduling now: Professors give us a list of the classes they're teaching with the time slots they'd prefer to teach, ranked in order of priority (most desired to least desired). Administration gives us a list of the rooms we may assign along with the times those rooms are available for our department's use. We start assigning professors to rooms trying (at first) to take into account the preferences of the various professors. Inevitably, conflicts arise, professors start asking for changes, and the plan falls to pieces somewhere around professor number 30, at which point we start assigning rooms basically wherever we can fit them in, crumpled pieces of paper are everywhere, and nobody's happy. (If you've ever wondered why your class was at 9.30 in the morning on Thursday but 4 pm every other day, now you know) I have been asked to quietly investigate whether software could do this more optimally. The Actual Question Is there an algorithm to efficiently schedule a set of resources such that the following criteria are met: The algorithm must never assign two professors to the same room at the same time. The task is not complete until every professor has been assigned a room / time. The algorithm need not worry about having too many professors for the amount of time slots available. (We're not that well funded.) As much as is possible the algorithm should respect the scheduling preferences of the individual professors. I feel like I can't be the first one to ask this. Is there a efficient algorithm for this, or is this the sort of problem that can only be brute-forced?

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Debugging Widget causes ANR

- by Salv0

I'm trying to debug an AppWidget but I incurred in a problem :D I placed a breakpoint on the top of the method: public void onReceive(Context context, Intent intent) { Log.v(TAG, "onReceive 1"); // BP on this line super.onReceive(context, intent); String action = intent.getAction(); // Checks on action and computations ... Log.v(TAG, "onReceive 2"); updateWidget(context); Log.v(TAG, "onReceive 3"); } The breakpoint stops the execution as expected but then the process dies. The problem is that the breakpoint ( I guess xD ) cause an ANR and the ActivityManager kills the process. That's the Log: 01-07 14:32:38.886: ERROR/ActivityManager(72): ANR in com.salvo.wifiwidget 01-07 14:32:38.886: INFO/Process(72): Sending signal. PID: 475 SIG: 9 ...... ...... 01-07 14:32:38.906: INFO/ActivityManager(72): Process com.salvo.wifiwidget (pid 475) has died. This cause the debug to stop. So the question is: there's a way to debug the widget without incurring in the ANR?? thanks in advance for the answers

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Why won't JPA delete owned entities when the owner entity loses the reference to them?

- by Nick

Hi! I've got a JPA entity "Request", that owns a List of Answers (also JPA entities). Here's how it's defined in Request.java: @OneToMany(cascade= CascadeType.ALL, mappedBy="request") private List<Answer> answerList; And in Answer.java: @JoinColumn(name = "request", referencedColumnName="id") @ManyToOne(optional = false) private Request request; In the course of program execution, the Request's List of Answers may have Answers added or removed from it, or the actual List object may be replaced. My problem is thus: when I merge a Request to the database, the Answer objects that used to be in the List are kept in the database -- that is, Answer objects that the Request no longer holds a reference to (indirectly, via a List) are not deleted. This is not the behaviour I desire, as if I merge a Request to the database, and then fetch it again, its Answers List may not be the same. Am I making some programming mistake? Is there an annotaion or setting that will ensure that the Answers in the database are exactly the Answers in the Request's List? A solution is to keep references to the original Answers List and then use the EntityManager to remove each old Answer before merging the Request, but it seems like there should be a cleaner way. Thank you!

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PHP Array to CSV

- by JohnnyFaldo

I'm trying to convert an array of products into a CSV file, but it doesn't seem to be going to plan. The CSV file is one long line, here is my code: for($i=0;$i<count($prods);$i++) { $sql = "SELECT * FROM products WHERE id = '".$prods[$i]."'"; $result = $mysqli->query($sql); $info = $result->fetch_array(); } $header = ''; for($i=0;$i<count($info);$i++) { $row = $info[$i]; $line = ''; for($b=0;$b<count($row);$b++) { $value = $row[$b]; if ( ( !isset( $value ) ) || ( $value == "" ) ) { $value = "\t"; } else { $value = str_replace( '"' , '""' , $value ); $value = '"' . $value . '"' . "\t"; } $line .= $value; } $data .= trim( $line ) . "\n"; } $data = str_replace( "\r" , "" , $data ); if ( $data == "" ) { $data = "\n(0) Records Found!\n"; } header("Content-type: application/octet-stream"); header("Content-Disposition: attachment; filename=your_desired_name.xls"); header("Pragma: no-cache"); header("Expires: 0"); print "$data"; Also, the header doesn't force a download. I've been copy and pasting the output and saving as .csv

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Pthread - setting scheduler parameters

- by Andna

I wanted to use read-writer locks from pthread library in a way, that writers have priority over readers. I read in my man pages that If the Thread Execution Scheduling option is supported, and the threads involved in the lock are executing with the scheduling policies SCHED_FIFO or SCHED_RR, the calling thread shall not acquire the lock if a writer holds the lock or if writers of higher or equal priority are blocked on the lock; otherwise, the calling thread shall acquire the lock. so I wrote small function that sets up thread scheduling options. void thread_set_up(int _thread) { struct sched_param *_param=malloc(sizeof (struct sched_param)); int *c=malloc(sizeof(int)); *c=sched_get_priority_min(SCHED_FIFO)+1; _param->__sched_priority=*c; long *a=malloc(sizeof(long)); *a=syscall(SYS_gettid); int *b=malloc(sizeof(int)); *b=SCHED_FIFO; if (pthread_setschedparam(*a,*b,_param) == -1) { //depending on which thread calls this functions, few thing can happen if (_thread == MAIN_THREAD) client_cleanup(); else if (_thread==ACCEPT_THREAD) { pthread_kill(params.main_thread_id,SIGINT); pthread_exit(NULL); } } } sorry for those a,b,c but I tried to malloc everything, still I get SIGSEGV on the call to pthread_setschedparam, I am wondering why?

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GTK+: How do I process RadioMenuItem choice without marking it chosen? And vise versa

- by eugene.shatsky

In my program, I've got a menu with a group of RadioMenuItem entries. Choosing one of them should trigger a function which can either succeed or fail. If it fails, this RadioMenuItem shouldn't be marked chosen (the previous one should persist). Besides, sometimes I want to set marked item without running the choice processing function. Here is my current code: # Update seat menu list def update_seat_menu(self, seats, selected_seat=None): seat_menu = self.builder.get_object('seat_menu') # Delete seat menu items for menu_item in seat_menu: # TODO: is it a good way? does remove() delete obsolete menu_item from memory? if menu_item.__class__.__name__ == 'RadioMenuItem': seat_menu.remove(menu_item) # Fill menu with new items group = [] for seat in seats: menu_item = Gtk.RadioMenuItem.new_with_label(group, str(seat[0])) group = menu_item.get_group() seat_menu.append(menu_item) if str(seat[0]) == selected_seat: menu_item.activate() menu_item.connect("activate", self.choose_seat, str(seat[0])) menu_item.show() # Process item choice def choose_seat(self, entry, seat_name): # Looks like this is called when item is deselected, too; must check if active if entry.get_active(): # This can either succeed or fail self.logind.AttachDevice(seat_name, '/sys'+self.device_syspath, True) Chosen RadioMenuItem gets marked irrespective of the choose_seat() execution result; and the only way to set marked item without triggering choose_seat() is to re-run update_seat_menu() with selected_seat argument, which is an overkill. I tried to connect choose_seat() with 'button-release-event' instead of 'activate' and call entry.activate() in choose_seat() if AttachDevice() succeeds, but this resulted in whole X desktop lockup until AttachDevice() timed out, and chosen item still got marked.

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Most effecient way to create a "slider" timeline in HTML, CSS, and JavaScript?

- by ZapChance

Alright, so here's my dilemma. I've got these two "slides" lined up, one ready to be passed into view. I have it working and all, but I can scroll over to the right to see the second slide! How could I have it you can only view the one slide? JavaScript used: function validate(form) { var user = form.username.value; var pass = form.password.value; if(user === "test") { if(pass === "pass") { var hideoptions = {"direction" : "left", "mode" : "hide"}; var showoptions = {"direction" : "left", "mode" : "show"}; /*$("#loginView").toggle("slide", hideoptions, 1000, function() { $("#loginView").css("margin-left", "100%"); }); $("#mainView").toggle("slide", showoptions, 1000, function() { $("#mainView").css("margin-left", 0); });*/ $("#loginView").animate({ marginLeft: "-100%" }, 1000); $("#mainView").animate({ marginLeft: "0" }, 1000); } else { alert("nope"); } } else { alert("nope 2"); } } As you can see here @ http://jsfiddle.net/D7Va3/1/ (JSFiddle), once you enter "test" and "pass", then click enter, the tiles slide. But. If you reload, you can see that you can scroll to the right of the screen and view the second slide prematurely, which is just not going to work for me. I still need to achieve the same seamless transition, but you must only be able to view one slide at a time. Also, I plan to expand with more slides, so if you're feeling lucky today, I'd really love to see an example of how I could support multiple frames. I'm very new to JavaScript (yet I know syntax rules, and general coding knowledge from other languages), so the better you explain, the more knowledgeable I can be, and I'd be very grateful for that. Thanks in advance!

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Need help with transferring data between MySQL db's using PHP

- by JM4

In one of the sites I manage, the client has decided to take on ACH/Bank Account administration where it was previously outsourced. As a result, the information submitted in our online form which used to simply store in a single database for processing now must sit in 'limbo' until the funds used for payment have been verified. My original plan is as follows: At the end of an enrollment, all form data is collected and stored in a single MySQL database. Our internal administrator will receive an email notification reminding him enrollments have taken place. He will process the ACH information collected and wait the 3-4 business days needed for payment to clear. Once the payment information has been returned as Good (haven't considered what I will do with the 'bad' yet), the administrator can log into a secure portal which allows him to click a button to 'process' the full information once compared and verified. the process is simplified as: Enrollment complete: data stored in DB 'A' Funds verified and link clicked: data from 'A' is copied to DB 'B' and 'A' is deleted. I have run similar processes with CSV output before and simply used //transfers old data to archive $transfer = mysql_query('INSERT INTO '.$archive.' SELECT * FROM '.$table) or die(mysql_error()); //empties existing table $query = mysql_query('TRUNCATE TABLE '.$table) or die(mysql_error()); but in those cases, ALL data returned was copied and deleted. I only want to copy and delete a single record. Any idea how to accomplish this?

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NSView only redraws on breakpoint

- by Jacopo

I have a custom view inside a NSPopover. It should change according to user input and it does the first time the user interact with it but it fails to redraw the following times. I have tried to put an NSLog inside the -drawRect: method and it doesn't get called during normal execution. When I try to debug and put a breakpoint inside the method it gets called normally and the app works as it should. I explicitly call the view -setNeedsDisplay: method every time I need it to redraw. I don't understand why it should make a difference. Here is the code that update the status of the view. These methods are part of the NSTextField delegate method -textDidChange: and I checked that these get called every time the user type something in the textfield associated with popover. [tokenCloud tokensToHighlight:[NSArray arrayWithObject:completeSuggestionString]]; tokenCloud.tokens = filteredTokens; [tokenCloud setNeedsDisplay:YES]; The views is a series of recessed button. The first line update the status of all the buttons in the popover and the second add or delete buttons. They both work properly because the first time they are called the view is update properly. I have also checked that both the status of the buttons in tokenCloud and its property tokens are updated correctly. The problem is that the NSView subclass, tokenCloud, doesn't redraw so the changes are not reflected in the UI the second time. Here is the draw method of the view: - (void)drawRect:(NSRect)rect { [self recalculateButtonLocations]; NSLog(@"Redrawn"); } Again this method gets called normally every time I update the view if I place a breakpoint in [self recalculateButtonLocations];. If instead I let the app run normally nothing gets logged in the console the second time I update the view. Same thing if I include the NSLog in the recalculateButtonLocations method, nothing gets logged the second time meaning that the method is not called.

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SQL Server insert performance with and without primary key

- by Eric

Summary: I have a table populated via the following: insert into the_table (...) select ... from some_other_table Running the above query with no primary key on the_table is ~15x faster than running it with a primary key, and I don't understand why. The details: I think this is best explained through code examples. I have a table: create table the_table ( a int not null, b smallint not null, c tinyint not null ); If I add a primary key, this insert query is terribly slow: alter table the_table add constraint PK_the_table primary key(a, b); -- Inserting ~880,000 rows insert into the_table (a,b,c) select a,b,c from some_view; Without the primary key, the same insert query is about 15x faster. However, after populating the_table without a primary key, I can add the primary key constraint and that only takes a few seconds. This one really makes no sense to me. More info: The estimated execution plan shows 0% total query time spent on the clustered index insert SQL Server 2008 R2 Developer edition, 10.50.1600 Any ideas?

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How to move positions within an array?

- by Jade Mulholland

A program that simply moves array elements. Two variables: userInputVariable and blankSpaceVariable. I have a 2D array named table. Defined as table[userInputVariable + 1][6] I am printing out this array in a table format, and the far left column is numbered by whatever number the user entered at the beginning of the program. I then ask the user where they would like to enter a blank space within the array. This blank space acts like a divider for all the other information in the array. For example, if the user enters 10 at the start for the userInputVariable, and then enters 5 for the blank space. Once printed, the numbers should go like this: 1, 2, 3, 4, --, 5, 6, 7, 8, 9, 10. My plan has been to create a for loop and try to move all the numbers in the array back a position starting from the blank space variable. What I currently have, but does not work: for (int i = blankSpaceVariable; i < table.length - 1; i++) { table[i] = table[i + 1]; } table[blankSpaceVariable] = "--"; With my current code, the numbers go like this: 1, 2, 3, 4, 6, 7, 8, 9, 10 Tried completing this a few different ways also, but the other info within my 2D array didn't move with the numbers. So I thought that this approach can hopefully move all the info within my 2D array down, and make way for a blank section. All help is greatly appreciated!

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License For (Mostly) Open Source Website / Service

- by Ryan Sullivan

I have an interesting setup and am not sure how to license a website. I know this is not legal advice, and I am not asking for any. There are so many different Open Source Licenses and I do not have the time to read every last one to see which best fits my situation. Really, I am looking for suggestions and a nudge in the right direction. My setup is: I give away for free version of my web service with a clean website interface. The implementation I use in the actual web site is (almost) identical to what I give away. The main service works the exactly the same way, but the website interface to manage features in the service is fairly different. Really the web interfaces have the same exact backend, and the front ends accomplish the same tasks, but the service I offer on my site is very rich and uses a good deal of javascript, where I kept the interface in the version I give away as simple and javascript-less as possible. Mostly so it is easy to understand and integrate into other sites. I am not entirely sure how I should license this. It is more like I develop an open source service but have a separate site built upon it. I like the GPLv3 but I am not sure if I can use it in this case especially since I am making some money off of google ad's on the site and plan on using amazon affiliates as well. Any help would be greatly appreciated. I do want to open it up as much as possible. But I still want to be able to continue with my own implementation. Thanks in advance for any information or help anyone can provide.

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Using the read function to read in a file.

- by robUK

Hello, gcc 4.4.1 I am using the read function to read in a wave file. However, when it gets to the read function. Execution seems to stop and freezes. I am wondering if I am doing anything wrong with this. The file size test-short.wave is: 514K. What I am aiming for is to read the file into the memory buffer chunks at a time. Currently I just testing this. Many thanks for any suggestions, #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <fcntl.h> #include <string.h> #include <unistd.h> int main(void) { char buff = malloc(10240); int32_t fd = 0; int32_t bytes_read = 0; char *filename = "test-short.wav"; /* open wave file */ if((fd = (open(filename, O_RDWR)) == -1)) { fprintf(stderr, "open [ %s ]\n", strerror(errno)); return 1; } printf("Opened file [ %s ]\n", filename); printf("sizeof(buff) [ %d ]\n", sizeof(buff)); printf("strlen(buff) [ %d ]\n", strlen(buff)); bytes_read = read(fd, buff, sizeof(buff)); printf("Bytes read [ %d ]\n", bytes_read); return 0; }

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How to speed-up a simple method? (possibily without changing interfaces or data structures)

- by baol

Hello. I have some data structures: all_unordered_mordered_m is a big vector containing all the strings I need (all different) ordered_m is a small vector containing the indexes of a subset of the strings (all different) in the former vector position_m maps the indexes of objects from the first vector to their position in the second one. The string_after(index, reverse) method returns the string referenced by ordered_m after all_unordered_m[index]. ordered_m is considered circular, and is explored in natural or reverse order depending on the second parameter. The code is something like the following: struct ordered_subset { // [...] std::vector<std::string>& all_unordered_m; // size = n >> 1 std::vector<size_t> ordered_m; // size << n std::map<size_t, size_t> position_m; // positions of strings in ordered_m const std::string& string_after(size_t index, bool reverse) const { size_t pos = position_m.find(index)->second; if(reverse) pos = (pos == 0 ? orderd_m.size() - 1 : pos - 1); else pos = (pos == ordered.size() - 1 ? 0 : pos + 1); return all_unordered_m[ordered_m[pos]]; } }; Given that: I do need all of the data-structures for other purposes; I cannot change them because I need to access the strings: by their id in the all_unordered_m; by their index inside the various ordered_m; I need to know the position of a string (identified by it's position in the first vector) inside ordered_m vector; I cannot change the string_after interface without changing most of the program. How can I speed up the string_after method that is called billions of times and is eating up about 10% of the execution time?

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Good C++ array class for dealing with large arrays of data in a fast and memory efficient way?

- by Shane MacLaughlin

Following on from a previous question relating to heap usage restrictions, I'm looking for a good standard C++ class for dealing with big arrays of data in a way that is both memory efficient and speed efficient. I had been allocating the array using a single malloc/HealAlloc but after multiple trys using various calls, keep falling foul of heap fragmentation. So the conclusion I've come to, other than porting to 64 bit, is to use a mechanism that allows me to have a large array spanning multiple smaller memory fragments. I don't want an alloc per element as that is very memory inefficient, so the plan is to write a class that overrides the [] operator and select an appropriate element based on the index. Is there already a decent class out there to do this, or am I better off rolling my own? From my understanding, and some googling, a 32 bit Windows process should theoretically be able address up to 2GB. Now assuming I've 2GB installed, and various other processes and services are hogging about 400MB, how much usable memory do you think my program can reasonably expect to get from the heap? I'm currently using various flavours of Visual C++.

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Planning a programming project by example (C# or C++)

- by Lunan

I am in the last year of undergraduate degree and i am stumped by the lack of example in c++ and c# large project in my university. All the mini project and assignment are based on text based database, which is so inefficient, and console display and command, which is frustrating. I want to develop a complete prototype of corporate software which deals in Inventory, Sales, Marketing, etc. Everything you would usually find in SAP. I am grateful if any of you could direct me to a books or article or sample program. Some of the question are : How to plan for this kind of programming? should i use the concept of 1 object(such as inventory) have its own process and program and have an integrator sit for all the program, or should i integrate it in 1 big program? How to build and address a database? i have little bit knowledge in database and i know SQL but i never address database in a program before. Database are table, and how do you suppose to represent a table in a OOP way? For development type, which is better PHP and C++ or C# and ASP.NET? I am planning to use Web Interface to set form and information, but using a background program to handle the compute. .NET is very much integrated and coding should be much faster, but i really wonder about performance if compared to PHP and C++ package thank you for the info

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Beginnerquestion: How to count amount of each number drawn in a Lottery and output it in a list?

- by elementz

I am writing this little Lottery application. Now the plan is, to count how often each number has been drawn during each iteration of the Lottery, and store this somewhere. My guess is that I would need to use a HashMap, that has 6 keys and increments the value by one everytime the respective keys number is drawn. But how would I accomplish this? My code so far: public void numberCreator() { // creating and initializing a Random generator Random rand = new Random(); // A HashMap to store the numbers picked. HashMap hashMap = new HashMap(); // A TreeMap to sort the numbers picked. TreeMap treeMap = new TreeMap(); // creating an ArrayList which will store the pool of availbale Numbers List<Integer>numPool = new ArrayList<Integer>(); for (int i=1; i<50; i++){ // add the available Numbers to the pool numPool.add(i); hashMap.put(nums[i], 0); } // array to store the lotto numbers int [] nums = new int [6]; for (int i =0; i < nums.length; i++){ int numPoolIndex = rand.nextInt(numPool.size()); nums[i] = numPool.get(numPoolIndex); // check how often a number has been called and store the new amount in the Map int counter = hashMap.get numPool.remove(numPoolIndex); } System.out.println(Arrays.toString(nums)); } Maybe someone can tell me if I have the right idea, or even how I would implement the map properly?

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