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  • How do I convert a simple ruby flashcard program into a ROR app?

    - by Mark Wilbur
    What I'm trying to do is make a basic flashcard app on rails. At this point, all I'm looking for is the functionality to iterate through a list of flashcards, quiz the user and let the user know if they were right or not. In ruby, it didn't take me long to write: class Card attr_accessor :answer, :question def initialize(answer = "", question="") @answer = answer @question = question end def quiz puts "What does #@question mean?" answer = gets.chomp if answer == @answer puts "Right" return true else puts "Wrong" return answer end end end class Cardlist attr_accessor :Cards def initialize(Cards = []) @Cards = Cards end def quiz Cards.each do |w| w.quiz end end end The problem I'm having with rails is figuring out where to put the logic to loop through all the cards in the list. I've made models specifying that Card belongs_to cardlist and that Cardlist has_many cards. I know application logic should go in the controller, but if I were to make a "quiz" action for my Cardlist controller, how would I make it iterate through all the cards? After each "quiz" page generated, I'd need to get an answer back from the user, respond (maybe flash) whether it was right or not and then continue onto the next question. Would any of that logic have to go into the view in order to make sure it's sending back the user inputted answers to the controller?

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  • Memory Leakage using datatables

    - by Vix
    Hi, I have situation in which i'm compelled to retrieve 30,000 records each to 2 datatables.I need to do some manipulations and insert into records into the SQL server in Manipulate(dt1,dt2) function.I have to do this in 15 times as you can see in the for loop.Now I want to know what would be the effective way in terms of memory usage.I've used the first approach.Please suggest me the best approach. (1) for (int i = 0; i < 15; i++) { DataTable dt1 = GetInfo(i); DataTable dt2 = GetData(i); Manipulate(dt1,dt2); } (OR) (2) DataTable dt1 = new DataTable(); DataTable dt2 = new DataTable(); for (int i = 0; i < 15; i++) { dt1=null; dt2=null; dt1 = GetInfo(); dt2 = GetData(); Manipulate(dt1, dt2); } Thanks, Vix.

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  • The correct usage of nested #pragma omp for directives

    - by GoldenLee
    The following code runs like a charm before OpenMP parallelization was applied. In fact, the following code was in a state of endless loop! I'm sure that's result from my incorrect use to the OpenMP directives. Would you please show me the correct way? Thank you very much. #pragma omp parallel for for (int nY = nYTop; nY <= nYBottom; nY++) { for (int nX = nXLeft; nX <= nXRight; nX++) { // Use look-up table for performance dLon = theApp.m_LonLatLUT.LonGrid()[nY][nX] + m_FavoriteSVISSRParams.m_dNadirLon; dLat = theApp.m_LonLatLUT.LatGrid()[nY][nX]; // If you don't want to use longitude/latitude look-up table, uncomment the following line //NOMGeoLocate.XYToGEO(dLon, dLat, nX, nY); if (dLon > 180 || dLat > 180) { continue; } if (Navigation.GeoToXY(dX, dY, dLon, dLat, 0) > 0) { continue; } // Skip void data scanline dY = dY - nScanlineOffset; // Compute coefficients as well as its four neighboring points' values nX1 = int(dX); nX2 = nX1 + 1; nY1 = int(dY); nY2 = nY1 + 1; dCx = dX - nX1; dCy = dY - nY1; dP1 = pIRChannelData->operator [](nY1)[nX1]; dP2 = pIRChannelData->operator [](nY1)[nX2]; dP3 = pIRChannelData->operator [](nY2)[nX1]; dP4 = pIRChannelData->operator [](nY2)[nX2]; // Bilinear interpolation usNomDataBlock[nY][nX] = (unsigned short)BilinearInterpolation(dCx, dCy, dP1, dP2, dP3, dP4); } }

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  • How can I hardcode input with the "select" system call in C?

    - by Archer
    If I understand this system call "select" correctly, it will loop waiting for user input from the keyboard or from an outside server. Every time I call "message_loop", I'm going to type in the same few lines of input each time. Is there a way to hard code this in so I don't have to type it in each time? void message_loop(FILE* fpin, FILE* fpout, Socket sock) { fd_set readfds, readfds_bak ; int in, max_fd, n, ret ; char buf[MAXMESG]; in = fileno(fpin) ; FD_ZERO(&readfds) ; FD_SET(in, &readfds) ; FD_SET(sock.socketfd, &readfds) ; readfds_bak = readfds ; max_fd = ((in > sock.socketfd) ? in : sock.socketfd) + 1 ; while(1){ readfds = readfds_bak ; /* select function */ if((ret = select(max_fd, &readfds, NULL, NULL, NULL)) < 0){ perror("select") ; break ; } else if (ret != 0) { if(FD_ISSET(in, &readfds)){ /* keyboard input */ fgets(buf, MAXMESG, fpin) ; if(send_message(buf, sock) == -1) break ; } if(FD_ISSET(sock.socketfd, &readfds)){ /* messages from server */ n = receive_message(buf, MAXMESG, &sock) ; if(n == -1) break ; else if(n > 0){ fputs(buf, fpout) ; fputc('\n', fpout) ; } fflush(stdout) ; } } } }

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  • jQuery Ajax loads URL multiple times, how do I unbind/rebind properly?

    - by gmoz22
    I load a SELECT element via Ajax (list of brands), get its selected value (brand id) and load another SELECT via another Ajax URL (list of templates for currently selected brand). Here's my code: $(document).ready( function() { // DO NOT cache Ajax calls $.ajaxSetup ({ cache: false }); // loader var ajax_load = "Loading..."; // Brands List URL var loadBrandUrl = "getBrandsList.php"; // Templates List URL var loadTemplateUrl = "getTemplatesList.php"; $("#brandslistSelect").html(ajax_load).load(loadBrandUrl) .ajaxComplete(function(){ // Brands select loaded /* Load Templates SELECT the first time since no .change() has happened */ var selectedBrand = $("#brandslistSelect option:selected").attr("value"); // get the value console.log(selectedBrand); // Log selected brand to console // get Templates select, commented for now since it does an infinite loop // $("#templateslistSelect").html(ajax_load).load(loadTemplateUrl, { BrandId: selectedBrand } ); /* End initial load template */ /* On interaction with the Brands SELECT */ $("#brandslistSelect").change(function () { // on interaction with select selectedBrand = $("#brandslistSelect option:selected").attr("value"); // get the value // get Templates SELECT $("#templateslistSelect").html(ajax_load).load(loadTemplateUrl, { BrandId: selectedBrand } ) }); /* End interaction with the Brands SELECT */ }); }); It returns selectedBrand in the console 3 times : selectedBrand = undefined selectedBrand = undefined selectedBrand = 101 Now, if I uncomment the following line, same output as above but it also loads the templates URL indefinitely : // $("#templateslistSelect").html(ajax_load).load(loadTemplateUrl, { BrandId: selectedBrand } ); Any idea how I could modify this code to make it work as intended? Thanks for your help stackOverflow community!

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  • Function calculating the probability of a letter in an sentence

    - by Mike
    I have a function that is supposed to calculate the number of times a letter occurs in a sentence, and based on that, calculate the probability of it occurring in the sentence. To accomplish this, I have a sentence: The Washington Metropolitan Area is the most educated and affluent metropolitan area in the United States. An array of structures, containing the letter, the number of times it occurs, and the probability of it occurring, with one structure for each letter character and an additional structure for punctuation and spaces: struct letters { char letter; int occur; double prob; }box[53]; This is the function itself: void probability(letters box[53], int sum { cout<<sum<<endl<<endl; for(int c8=0;c8<26;c8++) { box[c8].prob = (box[c8].occur/sum); cout<<box[c8].letter<<endl; cout<<box[c8].occur<<endl; cout<<box[c8].prob<<endl<<endl; } } It correctly identifies that there are 90 letters in the sentence in the first line, prints out the uppercase letter as per the structure in the second line of the for loop, and prints out the number of times it occurs. It continually prints 0 for the probability. What am I doing wrong?

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  • Faster quadrature decoder loops with Python code

    - by Kelei
    I'm working with a BeagleBone Black and using Adafruit's IO Python library. Wrote a simple quadrature decoding function and it works perfectly fine when the motor runs at about 1800 RPM. But when the motor runs at higher speeds, the code starts missing some of the interrupts and the encoder counts start to accumulate errors. Do you guys have any suggestions as to how I can make the code more efficient or if there are functions which can cycle the interrupts at a higher frequency. Thanks, Kel Here's the code: # Define encoder count function def encodercount(term): global counts global Encoder_A global Encoder_A_old global Encoder_B global Encoder_B_old global error Encoder_A = GPIO.input('P8_7') # stores the value of the encoders at time of interrupt Encoder_B = GPIO.input('P8_8') if Encoder_A == Encoder_A_old and Encoder_B == Encoder_B_old: # this will be an error error += 1 print 'Error count is %s' %error elif (Encoder_A == 1 and Encoder_B_old == 0) or (Encoder_A == 0 and Encoder_B_old == 1): # this will be clockwise rotation counts += 1 print 'Encoder count is %s' %counts print 'AB is %s %s' % (Encoder_A, Encoder_B) elif (Encoder_A == 1 and Encoder_B_old == 1) or (Encoder_A == 0 and Encoder_B_old == 0): # this will be counter-clockwise rotation counts -= 1 print 'Encoder count is %s' %counts print 'AB is %s %s' % (Encoder_A, Encoder_B) else: #this will be an error as well error += 1 print 'Error count is %s' %error Encoder_A_old = Encoder_A # store the current encoder values as old values to be used as comparison in the next loop Encoder_B_old = Encoder_B # Initialize the interrupts - these trigger on the both the rising and falling GPIO.add_event_detect('P8_7', GPIO.BOTH, callback = encodercount) # Encoder A GPIO.add_event_detect('P8_8', GPIO.BOTH, callback = encodercount) # Encoder B # This is the part of the code which runs normally in the background while True: time.sleep(1)

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  • VLC ActivX plugin not playing video in update IE9

    - by Prashant Mehta
    I am using vlc ActiveX plugin on web browser IE9 to play video live streaming. Its work perfect in IE8 but when I update browser from IE8 to IE9 than it not playing video file or live straming. here is my code. <object type="application/x-vlc-plugin" id="vlc" width="517" height="388" classid="clsid:9BE31822-FDAD-461B-AD51-BE1D1C159921"> <param name="MRL" id="mrlVideo" value="" /> <param name="volume" value="50" /> <param name="autoplay" value="True" /> <param name="loop" value="false" /> <param name="fullscreen" value="false" /> <param name="wmode" value="transparent" /> <param name="toolbar" value="true" /> <param name="windowless" value="true" /> </object> and in javascript I am using these var vlc = document.getElementById("vlc"); var options = new Array(":rtsp-tcp"); var urlVideofile = "hppt://IP:portnumber/" var id = vlc.playlist.add(urlVideofile, null, options); vlc.playlist.playItem(id); Here is attach image that showing what exactly error is coming Any help is greatly appreciated Thanks.

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  • c# Convert LINQ var result to actual type

    - by DrBob
    In c#, Given the following code: public class Person { public int PersonID { get; set; } public int Age { get; set; } public string Name { get; set; } } and List<Person> people = new List<Person>(); for (int i = 0; i != 15; i++) { Person p = new Person(); p.PersonID = i; p.Age = i * 12; p.Name = "Name " + i; people.Add(p); } var sortedPeople = from qPeople in people where qPeople.Age > 0 && qPeople.Age < 25 || qPeople.Age > 100 orderby qPeople.Age descending select qPeople; Can I load the results of sortedPeople back into a List<Person without a loop? Thanks.

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  • C release dynamically allocated memory

    - by user1152463
    I have defined function, which returns multidimensional array. allocation for rows arr = (char **)malloc(size); allocation for columns (in loop) arr[i] = (char *)malloc(v); and returning type is char** Everything works fine, except freeing the memory. If I call free(arr[i]) and/or free(arr) on array returned by function, it crashes. Thanks for help EDIT:: allocating fuction pole = malloc(zaznamov); char ulica[52], t[52], datum[10]; float dan; int i = 0, v; *max = 0; while (!is_eof(f)) { get_record(t, ulica, &dan, datum, f); v = strlen(ulica) - 1; pole[i] = malloc(v); strcpy(pole[i], ulica); pole[i][v] = '\0'; if (v > *max) { *max = v; } i++; } return pole;` part of main where i am calling function pole = function(); releasing memory int i; for (i = 0; i < zaznamov; i++) { free(pole[i]); pole[i] = NULL; } free(pole); pole = NULL;

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  • How to draw shadows that don't suck?

    - by mystify
    A CAShapeLayer uses a CGPathRef to draw it's stuff. So I have a star path, and I want a smooth drop shadow with a radius of about 15 units. Probably there is some nice functionality in some new iPhone OS versions, but I need to do it myself for a old aged version of 3.0 (which most people still use). I tried to do some REALLY nasty stuff: I created a for-loop and sequentially created like 15 of those paths, transform-scaling them step by step to become bigger. Then assigning them to a new created CAShapeLayer and decreasing it's alpha a little bit on every iteration. Not only that this scaling is mathematically incorrect and sucks (it should happen relative to the outline!), the shadow is not rounded and looks really ugly. That's why nice soft shadows have a radius. The tips of a star shouldn't appear totally sharp after a shadow size of 15 units. They should be soft like cream. But in my ugly solution they're just as s harp as the star itself, since all I do is scale the star 15 times and decrease it's alpha 15 times. Ugly. I wonder how the big guys do it? If you had an arbitrary path, and that path must throw a shadow, how does the algorithm to do that work? Probably the path would have to be expanded like 30 times, point-by-point relative to the tangent of the outline away from the filled part, and just by 0.5 units to have a nice blending. Before I re-invent the wheel, maybe someone has a handy example or link?

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  • Timeout Exceptions

    - by Raihan Jamal
    This is my below code, I am confuse why this thing is happening. In this code getLocationByIpTimeout is a method in which I am passing two things- one is the ip address and second is the timeout. So I will get the timeout exception if the response is not getting back in under 5 ms. So when I ran this below code, I am getting few timeout exceptions but the most important thing that I am confuse is if I am getting timeout exceptions (time taken to get the response is greater than 5 ms) then why the program is entering in that if loop in which I am having difference 5. What can be the possible reason for this? It is because of catch block?? Any suggestions will be appreciated. long runs =10000; long difference = 0; while(runs > 0) { String ipAddress = generateIPAddress(); long start_time = System.nanoTime(); try { resp = PersonalizationGeoLocationServiceClientHelper.getLocationByIpTimeout(ipAddress, 5); } catch (TimeoutException e) { System.out.println("Timeout Exception"); } long end_time = System.nanoTime(); if(resp == null || (resp.getLocation() == null)) { difference = 0; } else if(resp.getLocation() != null) { difference = (end_time - start_time)/1000000; } if(difference> 5) { System.out.println("Debug"); } }

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  • R: building a simple command line plotting tool/Capturing window close events

    - by user275455
    I am trying to use R within a script that will act as a simple command line plot tool. I.e. user pipes in a csv file and they get a plot. I can get to R fine and get the plot to display through various temp file machinations, but I have hit a roadblock. I cannot figure out how to get R to keep running until the users closes the window. If I plot and exit, the plot disappears immediately. If I plot and use some kind of infinite loop, the user cannot close the plot; he must exit by using an interrupt which I don't like. I see there is a getGraphicsEvent function, but it claims that the device is not supported (X11). Anyway, it doesn't appear to actually support an onClose event, only onMouseDown. Any ideas on how to solve this? edit: Thanks to Dirk for the advice to check out the tk interface. Here is the test code that works: require(tcltk) library(tkrplot) ##function to display plot, called by tkrplot and embedded in a window plotIt<-function(){ plot(x=1:10, y=1:10) } ##create top level window tt<-tktoplevel() ##variable to wait on like a condition variable, to be set by event handler done <- tclVar(0) ##bind to the window destroy event, set done variable when destroyed tkbind(tt,"",function() tclvalue(done) <- 1) ##Have tkrplot embed the plot window, then realize it with tkgrid tkgrid(tkrplot(tt,plotIt)) ##wait until done is true tkwait.variable(done)

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  • Adding up fractions in PHP

    - by Gamemorize
    I would like to create a loop that keeps adding a set fraction, here in my example 1/3, and which later I can check against for matches with integer values. Obviously when php adds 1/3 + 1/3 + 1/3 the result is 0.9999999, so i thought I could use the occasional round to help me, but this isn't working either. The idea that I had would be that .333 + .333 becomes .666 and that if rounded that would become .667, then + .333 and the result is 1. However round only seems to work, for me, if the number of digits actually decreases. so round (0.666, 3) remains 0.666 <?php $denom = 3; $frac = 1/$denom; $frac = round($frac,3); $value = 0; $max =24; for($f = 1; $f <= $max; $f++){ echo "old value is now at ".$value.".<br/>"; $value = $value+$frac; echo "value is now at ".$value.".<br/>"; $value = round($value,3); echo "rounded value is now at ".$value.".<br/>"; $valueArray[$f] = $value; //and here for ease of testing.... if (($value==1)OR ($value==2)OR ($value==3)OR ($value==4)OR ($value==5)OR ($value==6)OR ($value==7)OR ($value==8)){ echo "match!<br/>"; }else{ echo "no match!<br/>"; } } ?> Am I going about this in a totally stupid way? Accuracy when the value is not an integer is not needed, just that it can == with integers.

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  • Opencv video frame not showing Sobel output

    - by user1016950
    This is a continuation question from Opencv video frame giving me an error I think I closed it off, Im new to Stackoverflow. I have code below that Im trying to see its Sobel edge image. However the program runs but the output is just a grey screen where if I mouseover the cursor disappears. Does anyone see the error? or is it a misunderstanding about the data structures Im using IplImage *frame, *frame_copy = 0; // capture frames from video CvCapture *capture = cvCaptureFromFile( "lightinbox1.avi"); //Allows Access to video propertys cvQueryFrame(capture); //Get the number of frames int nframe=(int) cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_COUNT); //Name window cvNamedWindow( "video:", 1 ); //start loop for(int i=0;i<nframe;i++){ //prepare capture frame extraction cvGrabFrame(capture); cout<<"We are on frame "<<i<<"\n"; //Get this frame frame = cvRetrieveFrame( capture ); con2txt(frame); frame_copy = cvCreateImage(cvSize(frame->width,frame->height),IPL_DEPTH_8U,frame->nChannels ); //show and destroy frame cvCvtColor( frame,frame,CV_RGB2GRAY); //Create Sobel output frame_copy1 = cvCreateImage(cvSize(frame->width,frame->height),IPL_DEPTH_16S,1 ); cvSobel(frame_copy,frame_copy1,2,2,3); cvShowImage("video:",frame_copy1); cvWaitKey(33);} cvReleaseCapture(&capture);

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  • Questions on Juval Lowy's IDesign C# Coding Standard

    - by Jan
    We are trying to use the IDesign C# Coding standard. Unfortunately, I found no comprehensive document to explain all the rules that it gives, and also his book does not always help. Here are the open questions that remain for me (from chapter 2, Coding Practices): No. 26: Avoid providing explicit values for enums unless they are integer powers of 2 No. 34: Always explicitly initialize an array of reference types using a for loop No. 50: Avoid events as interface members No. 52: Expose interfaces on class hierarchies No. 73: Do not define method-specific constraints in interfaces No. 74: Do not define constraints in delegates Here's what I think about those: I thought that providing explicit values would be especially useful when adding new enum members at a later point in time. If these members are added between other already existing members, I would provide explicit values to make sure the integer representation of existing members does not change. No idea why I would want to do this. I'd say this totally depends on the logic of my program. I see that there is alternative option of providing "Sink interfaces" (simply providing already all "OnXxxHappened" methods), but what is the reason to prefer one over the other? Unsure what he means here: Could this mean "When implementing an interface explicitly in a non-sealed class, consider providing the implementation in a protected virtual method that can be overridden"? (see Programming .NET Components 2nd Edition, end of chapter “Interfaces and Class Hierarchies”). I suppose this is about providing a "where" clause when using generics, but why is this bad on an interface? I suppose this is about providing a "where" clause when using generics, but why is this bad on a delegate?

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  • Trie Backtracking in Recursion

    - by Darksky
    I am building a tree for a spell checker with suggestions. Each node contains a key (a letter) and a value (array of letters down that path). So assume the following sub-trie in my big trie: W / \ a e | | k k | | is word--> e e | ... This is just a subpath of a sub-trie. W is a node and a and e are two nodes in its value array etc... At each node, I check if the next letter in the word is a value of the node. I am trying to support mistyped vowels for now. So 'weke' will yield 'wake' as a suggestion. Here's my searchWord function in my trie: def searchWord(self, word, path=""): if len(word) > 0: key = word[0] word = word[1:] if self.values.has_key(key): path = path + key nextNode = self.values[key] return nextNode.searchWord(word, path) else: # check here if key is a vowel. If it is, check for other vowel substitutes else: if self.isWord: return path # this is the word found else: return None Given 'weke', at the end when word is of length zero and path is 'weke', my code will hit the second big else block. weke is not marked as a word and so it will return with None. This will return out of searchWord with None. To avoid this, at each stack unwind or recursion backtrack, I need to check if a letter is a vowel and if it is, do the checking again. I changed the if self.values.has_key(key) loop to the following: if self.values.has_key(key): path = path + key nextNode = self.values[key] ret = nextNode.searchWord(word, path) if ret == None: # check if key == vowel and replace path # return nextNode.searchWord(... return ret What am I doing wrong here? What can I do when backtracking to achieve what I'm trying to do?

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  • Why does this log output show the same answer in each iteration?

    - by Will Hancock
    OK, I was reading an article on optimising JS for Googles V8 engine, when i saw this code example... I nearly skimmed over it, but then I saw this; |=; a[0] |= b; a = new Array(); a[0] = 0; for (var b = 0; b < 10; b++) { console.log(a, b) a[0] |= b; // Much better! 2x faster. } a[0] |= b; So I ran it, in my console, with a console.log in the loop and resulted in 15; [15] 0 [15] 1 [15] 2 [15] 3 [15] 4 [15] 5 [15] 6 [15] 7 [15] 8 [15] 9 WHAT?!?! Where the hell does it get 15 from, on every iteration?!?!?! I've been a web dev for 7 years, and this has stumped me and a fellow colleague. Can somebody talk me through this code? Cheers.

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  • Django Datetime field question

    - by Shehzad009
    Hello I have been having a problem with django while trying to work with datetime. In my webapp I have a table like so when I run server. ID Owing 1 -100 (All the same value) 2 -100 3 -100 . . . . . . It has in one column Invoice id and the other owing. One-one relationship as well. sow for example owing value for 1 is 100. Unfortunately, this is where it all goes wrong because throughout column (Owing), it is giving me the owing value for ID=1. I want each ID to give me their owing value. Here is my view. I also wonder if I may need a for loop somewhere as well. def homepage(request): invoices_list = Invoice.objects.all() invoice_name = invoices_list[0].client_contract_number.client_number.name invoice_gross = invoices_list[0].invoice_gross payment_date = invoices_list[0].payment_date if payment_date <= datetime.now(): owing = invoice_gross if payment_date > datetime.now(): owing = 0 else: owing= 0 return render_to_response(('index.html', locals()), {'invoices_list': invoices_list ,'invoice_number':invoice_number, 'invoice_name':invoice_name, 'invoice_gross':invoice_gross, 'payment_date':payment_date, 'owing': owing}, context_instance=RequestContext(request)) EDIT: Here is my template. The thing is the function owing is not in my models so saying {{invoices.owing}} wont work. {% for invoices in invoices_list %} <tr> <td>{{invoices.invoice_number}}</td> <td>{{invoices.invoice_contact}}</td> <td>{{invoices.client_contract_number}}</td> <td>{{invoices.payment_date|date:"d M Y"}}</td> <td>{{invoices.invoice_gross}}</td> <td>{{owing}}</td> {% endfor %}

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  • Goldbach theory in C

    - by nofe
    I want to write some code which takes any positive, even number (greater than 2) and gives me the smallest pair of primes that sum up to this number. I need this program to handle any integer up to 9 digits long. My aim is to make something that looks like this: Please enter a positive even integer ( greater than 2 ) : 10 The first primes adding : 3+7=10. Please enter a positive even integer ( greater than 2 ) : 160 The first primes adding : 3+157=160. Please enter a positive even integer ( greater than 2 ) : 18456 The first primes adding : 5+18451=18456. I don't want to use any library besides stdio.h. I don't want to use arrays, strings, or anything besides for the most basic toolbox: scanf, printf, for, while, do-while, if, else if, break, continue, and the basic operators (<,, ==, =+, !=, %, *, /, etc...). Please no other functions especially is_prime. I know how to limit the input to my needs so that it loops until given a valid entry. So now I'm trying to figure out the algorithm. I thought of starting a while loop like something like this: #include <stdio.h> long first, second, sum, goldbach, min; long a,b,i,k; //indices int main (){ while (1){ printf("Please enter a positive integer :\n"); scanf("%ld",&goldbach); if ((goldbach>2)&&((goldbach%2)==0)) break; else printf("Wrong input, "); } while (sum!=goldbach){ for (a=3;a<goldbach;a=(a+2)) for (i=2;(goldbach-a)%i;i++) first = a; for (b=5;b<goldbach;b=(b+2)) for (k=2;(goldbach-b)%k;k++) sum = first + second; } }

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  • Callbacks on GUI Thread

    - by miguel
    We have an external data provider which, in its construtor, takes a callback thread for returning data upon. There are some issues in the system which I am suspicious are related to threading, however, in theory they cannot be, due to the fact that the callbacks should all be returned on the same thread. My question is, does code like this require thread synchronisation? class Foo { ExternalDataProvider _provider; public Foo() { // This is the c'tor for the xternal data provider, taking a callback loop as param _provider = new ExternalDataProvider(UILoop); _provider.DataArrived += ExternalProviderCallbackMethod; } public ExternalProviderCallbackMethod() { var itemArray[] = new String[4] { "item1", "item2", "item3", "item4" }; for (int i = 0; i < itemArray.Length; i++) { string s = itemArray[i]; switch(s) { case "item1": DoItem1Action(); break; case "item2": DoItem2Action(); break; default: DoDefaultAction(); break; } } } } The issue is that, very infrequently, DoItem2Action is executingwhen DoItem1Action should be exectuing. Is it at all possible threading is at fault here? In theory, as all callbacks are arriving on the same thread, they should be serialized, right? So there should be no need for thread sync here?

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  • How to insert several thousand columns into sqlite3?

    - by user291071
    Similar to my last question, but I ran into problem lets say I have a simple dictionary like below but its Big, when I try inserting a big dictionary using the methods below I get operational error for the c.execute(schema) for too many columns so what should be my alternate method to populate an sql databases columns? Using the alter table command and add each one individually? import sqlite3 con = sqlite3.connect('simple.db') c = con.cursor() dic = { 'x1':{'y1':1.0,'y2':0.0}, 'x2':{'y1':0.0,'y2':2.0,'joe bla':1.5}, 'x3':{'y2':2.0,'y3 45 etc':1.5} } # 1. Find the unique column names. columns = set() for _, cols in dic.items(): for key, _ in cols.items(): columns.add(key) # 2. Create the schema. col_defs = [ # Start with the column for our key name '"row_name" VARCHAR(2) NOT NULL PRIMARY KEY' ] for column in columns: col_defs.append('"%s" REAL NULL' % column) schema = "CREATE TABLE simple (%s);" % ",".join(col_defs) c.execute(schema) # 3. Loop through each row for row_name, cols in dic.items(): # Compile the data we have for this row. col_names = cols.keys() col_values = [str(val) for val in cols.values()] # Insert it. sql = 'INSERT INTO simple ("row_name", "%s") VALUES ("%s", "%s");' % ( '","'.join(col_names), row_name, '","'.join(col_values) )

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  • Computation overhead in C# - Using getters/setters vs. modifying arrays directly and casting speeds

    - by Jeffrey Kern
    I was going to write a long-winded post, but I'll boil it down here: I'm trying to emulate the graphical old-school style of the NES via XNA. However, my FPS is SLOW, trying to modify 65K pixels per frame. If I just loop through all 65K pixels and set them to some arbitrary color, I get 64FPS. The code I made to look-up what colors should be placed where, I get 1FPS. I think it is because of my object-orented code. Right now, I have things divided into about six classes, with getters/setters. I'm guessing that I'm at least calling 360K getters per frame, which I think is a lot of overhead. Each class contains either/and-or 1D or 2D arrays containing custom enumerations, int, Color, or Vector2D, bytes. What if I combined all of the classes into just one, and accessed the contents of each array directly? The code would look a mess, and ditch the concepts of object-oriented coding, but the speed might be much faster. I'm also not concerned about access violations, as any attempts to get/set the data in the arrays will done in blocks. E.g., all writing to arrays will take place before any data is accessed from them. As for casting, I stated that I'm using custom enumerations, int, Color, and Vector2D, bytes. Which data types are fastest to use and access in the .net Framework, XNA, XBox, C#? I think that constant casting might be a cause of slowdown here. Also, instead of using math to figure out which indexes data should be placed in, I've used precomputed lookup tables so I don't have to use constant multiplication, addition, subtraction, division per frame. :)

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  • pthread_join from a signal handler

    - by liv2hak
    I have a capture program which in addition do capturing data and writing it into a file also prints some statistics.The function that prints the statistics static void* report(void) { /*Print statistics*/ } is called roughly every second using an ALARM that expires every second.So The program is like void capture_program() { pthread_t report_thread while(!exit_now) { if(pthread_create(&report_thread,NULL,report,NULL)){ fprintf(stderr,"Error creating reporting thread! \n"); } /* Capturing code -------------- -------------- */ if(doreport) usleep(5); } } void *report(void *param) { while(true) { if(doreport) { doreport = 0 //access some register from hardware usleep(5) } } } The expiry of the timer sets the doreport flag.If this flag is set report() is called which clears the flag.I am using usleep to alternate between two threads in the program.This seems to work fine. I also have a signal handler to handle SIGINT (i.e CTRL+C) static void anysig(int sig) { if (sig != SIGINT) dagutil_set_signal_handler(SIG_DFL); /* Tell the main loop to exit */ exit_now = 1; return; } My question: 1) Is it safe to call pthread_join from inside the signal handler? 2) Should I use exit_now flag for the report thread as well?

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  • All Callbacks on GUI Thread - Multithreading issues possible?

    - by miguel
    We have an external data provider which, in its construtor, takes a callback thread for returning data upon. There are some issues in the system which I am suspicious are related to threading, however, in theory they cannot be, due to the fact that the callbacks should all be returned on the same thread. My question is, does code like this require thread synchronisation? class Foo { ExternalDataProvider _provider; public Foo() { // This is the c'tor for the xternal data provider, taking a callback loop as param _provider = new ExternalDataProvider(UILoop); _provider.DataArrived += ExternalProviderCallbackMethod; } public ExternalProviderCallbackMethod(...) { //...(code omitted) var itemArray[] = new String[4] { "item1", "item2", "item3", "item4" }; for (int i = 0; i < itemArray.Length; i++) { string s = itemArray[i]; switch(s) { case "item1": DoItem1Action(); break; case "item2": DoItem2Action(); break; default: DoDefaultAction(); break; } //...(code omitted) } } } The issue is that, very infrequently, DoItem2Action is executingwhen DoItem1Action should be exectuing. Is it at all possible threading is at fault here? In theory, as all callbacks are arriving on the same thread, they should be serialized, right? So there should be no need for thread sync here?

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