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  • GOTO still considered harmful?

    - by Kyle Cronin
    Everyone is aware of Dijkstra's Letters to the editor: go to statement considered harmful (also here .html transcript and here .pdf) and there has been a formidable push since that time to eschew the goto statement whenever possible. While it's possible to use goto to produce unmaintainable, sprawling code, it nevertheless remains in modern programming languages. Even the advanced continuation control structure in Scheme can be described as a sophisticated goto. What circumstances warrant the use of goto? When is it best to avoid? As a followup question: C provides a pair of functions, setjmp and longjmp, that provide the ability to goto not just within the current stack frame but within any of the calling frames. Should these be considered as dangerous as goto? More dangerous? Dijkstra himself regretted that title, of which he was not responsible for. At the end of EWD1308 (also here .pdf) he wrote: Finally a short story for the record. In 1968, the Communications of the ACM published a text of mine under the title "The goto statement considered harmful", which in later years would be most frequently referenced, regrettably, however, often by authors who had seen no more of it than its title, which became a cornerstone of my fame by becoming a template: we would see all sorts of articles under the title "X considered harmful" for almost any X, including one titled "Dijkstra considered harmful". But what had happened? I had submitted a paper under the title "A case against the goto statement", which, in order to speed up its publication, the editor had changed into a "letter to the Editor", and in the process he had given it a new title of his own invention! The editor was Niklaus Wirth. A well thought out classic paper about this topic, to be matched to that of Dijkstra, is Structured Programming with go to Statements (also here .pdf), by Donald E. Knuth. Reading both helps to reestablish context and a non-dogmatic understanding of the subject. In this paper, Dijkstra's opinion on this case is reported and is even more strong: Donald E. Knuth: I believe that by presenting such a view I am not in fact disagreeing sharply with Dijkstra's ideas, since he recently wrote the following: "Please don't fall into the trap of believing that I am terribly dogmatical about [the go to statement]. I have the uncomfortable feeling that others are making a religion out of it, as if the conceptual problems of programming could be solved by a single trick, by a simple form of coding discipline!"

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  • iPhone :Can we add more than One application in a Single application

    - by iPhone Fun
    Hi all, I do have an Idea to integrate with my application. I want to create multiple application within a single one application. Like and application containing Weather application as well as image processing application + camera based application. I want to know Is this thing possible with iphone application? Please suggest me is this possible with iPhone app development and is it allowed by apple or not. thanks for your suggestion in advance.

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  • What are some best practices for structuring cherrypy apps?

    - by Omega
    I'm writing a cherrypy app and I was wondering what the best way is for structuring my handlers and code for larger applications? I realize assignment is simple trough cherrypy.root, but what are some practices for writing the handlers and assigning them? (Allow me to prove my confusion!) My initial thought is to write a standard handler class that infers a template to run based on the current URL or class/method combination. Then I would assign one instance of that handler multiple times to the path to create pages. I don't see this working however as the recursive references wouldn't work quite right. So, given the fact that I'm already drawing blanks on how my own source code should look, I'd love some pointers and examples! Feel free to ask some detailed questions for me to clarify. While there is plenty of cherrypy tutorial material out there, it tends to only scratch the surface.

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  • R plot- SGAM plot counts vs. time - how do I get dates on the x-axis?

    - by Nate
    I'd like to plot this vs. time, with the actual dates (years actually, 1997,1998...2010). The dates are in a raw format, ala SAS, days since 1960 (hence as.date conversion). If I convert the dates using as.date to variable x, and do the GAM plot, I get an error. It works fine with the raw day numbers. But I want the plot to display the years (data are not equally spaced). structure(list(site = c(928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L, 928L), date = c(13493L, 13534L, 13566L, 13611L, 13723L, 13752L, 13804L, 13837L, 13927L, 14028L, 14082L, 14122L, 14150L, 14182L, 14199L, 16198L, 16279L, 16607L, 16945L, 17545L, 17650L, 17743L, 17868L, 17941L, 18017L, 18092L), y = c(7L, 7L, 17L, 18L, 17L, 17L, 10L, 3L, 17L, 24L, 11L, 5L, 5L, 3L, 5L, 14L, 2L, 9L, 9L, 4L, 7L, 6L, 1L, 0L, 5L, 0L)), .Names = c("site", "date", "y"), class = "data.frame", row.names = c(NA, -26L)) sgam1 <- gam(sites$y ~ s(sites$date)) sgam <- predict(sgam1, se=TRUE) plot(sites$date,sites$y,xaxt="n", xlab='Time', ylab='Counts') x<-as.Date(sites$date, origin="1960-01-01") axis(1, at=1:26,labels=x) lines(sites$date,sgam$fit, lty = 1) lines(sites$date,sgam$fit + 1.96* sgam$se, lty = 2) lines(sites$date,sgam$fit - 1.96* sgam$se, lty = 2) ggplot2 has a solution (it doesn't mind the as.date thing) but it gives me other problems...

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  • Is C# fast enough for games

    - by Matt
    Will a game written in C# have any speed issues after long periods of play, like for 24 hours at a time? I'm specifically talking about a 2D RPG similar to old Final Fantasy or Dragon Quest games. I know that languages like Python will slow down too much, curious how C# would stand.

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  • java Properties - to expose or not to expose?

    - by ring bearer
    This might be an age old problem and I am sure everyone has their own ways. Suppose I have some properties defined such as secret.user.id=user secret.password=password website.url=http://stackoverflow.com Suppose I have 100 different classes and places where I need to use these properties. Which one is good (1) I create a Util class that will load all properties and serve them using a key constant Such as : Util is a singleton that loads all properties and keeps up on getInstance() call. Util myUtil = Util.getInstance(); String user = myUtil.getConfigByKey(Constants.SECRET_USER_ID); String password = myUtil.getConfigByKey(Constants.SECRET_PASSWORD); .. //getConfigByKey() - inturns invokes properties.get(..) doSomething(user, password) So wherever I need these properties, I can do steps above. (2) I create a meaningful Class to represent these properties; say, ApplicationConfig and provide getters to get specific properties. So above code may look like: ApplicationConfig config = ApplicationConfig.getInstance(); doSomething(config.getSecretUserId(), config.getPassword()); //ApplicationConfig would have instance variables that are initialized during // getInstance() after loading from properties file. Note: The properties file as such will have only minor changes in the future. My personal choice is (2) - let me hear some comments?

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  • How to exit SW quickly

    - by Yigang Wu
    I have a SW which reside in external HDD, it will run automatically when user plug external HDD, of course, the SW have to close automatically when user unplug the external HDD. I can receive the device lost message, however my SW will not be respond druing releasing all objects, if I call exit(0) directly, the SW will show a crash message. Is there any way to quickly exit SW?

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  • Weird bug in Java try-catch-finally

    - by kcr
    I'm using JODConverter to convert .xls and .ppt to .pdf format. For this i have code something like try{ //do something System.out.println("connecting to open office"); OpenOfficeConnection connection = new SocketOpenOfficeConnection(8100); System.out.println("connection object created"); connection.connect(); System.out.println("connection to open office successful"); //do something if(!successful) throw new FileNotFoundException(); }catch(Exception e){ System.out.println("hello here"); System.out.println("Caught Exception while converting to PDF "); LOGGER.error("Error in converting media" + e.getMessage()); throw new MediaConversionFailedException(); }finally{ decode_pdf.closePdfFile(); System.out.println("coming in finally"); //do something here } My Output : connecting to open office connection object created coming in finally P.S. return type of method is void How is it possible ? Even if there is some problem in connection.connect(), it s'd come in catch block. confused

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  • The Reason of Service Termination

    - by Mariusz
    I use a service application I created in Delphi. My problem is that it is sometimes terminated by the operating system and I don't know why this happens. When I go the the system events, I can find a piece of information like this one: Event ID: 7034, The [...] service terminated unexpectedly. It has done this [...] time(s). I know you can't give me an answer why this happens, but could you please give me a clue what to pay attention to to find the reason of that behaviour? For instance what kind of exceptions could make the OS close an application. Thank you in advance.

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  • How to solve such system with given parts of it? (maple)

    - by Kabumbus
    So I had a system #for given koefs k:=3; n:=3; #let us solve system: koefSolution:= solve({ sum(a[i], i = 0 .. k) = 0, sum(a[i], i = 0 .. k)-(sum(b[i], i = 0 .. k)) = 0, sum(i^n*a[i], i = 0 .. k)-(sum(i^(n-1)*b[i], i = 0 .. k)) = 0 }); So I have a vector like koefSolution := { a[0] = 7*a[2]+26*a[3]-b[1]-4*b[2]-9*b[3], a[1] = -8*a[2]-27*a[3]+b[1]+4*b[2]+9*b[3], a[2] = a[2], a[3] = a[3], b[0] = -b[1]-b[2]-b[3], b[1] = b[1], b[2] = b[2], b[3] = b[3]} I have a[0] so I try solve({koefSolution, a[0] = 1}); why it does not solve my system for given a[0]? ( main point here is to fill koefSolution with given a[] and b[] and optimize.)

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  • Segmentation fault in my C program

    - by user233542
    I don't understand why this would give me a seg fault. Any ideas? This is the function that returns the signal to stop the program (plus the other function that is called within this): double bisect(double A0,double A1,double Sol[N],double tol,double c) { double Amid,shot; while (A1-A0 > tol) { Amid = 0.5*(A0+A1); shot = shoot(Sol, Amid, c); if (shot==2.*Pi) { return Amid; } if (shot > 2.*Pi){ A1 = Amid; } else if (shot < 2.*Pi){ A0 = Amid; } } return 0.5*(A1+A0); } double shoot(double Sol[N],double A,double c) { int i,j; /*Initial Conditions*/ for (i=0;i<buff;i++) { Sol[i] = 0.; } for (i=buff+l;i<N;i++) { Sol[i] = 2.*Pi; } Sol[buff]= 0; Sol[buff+1]= A*exp(sqrt(1+3*c)*dx); for (i=buff+2;i<buff+l;i++) { Sol[i] = (dx*dx)*( sin(Sol[i-1]) + c*sin(3.*(Sol[i-1])) ) - Sol[i-2] + 2.*Sol[i-1]; } return Sol[i-1]; } The values buff, l, N are defined using a #define statement. l = 401, buff = 50, N = 2000 Here is the full code: #include <stdio.h> #include <stdlib.h> #include <math.h> #define w 10 /*characteristic width of a soliton*/ #define dx 0.05 /*distance between lattice sites*/ #define s (2*w)/dx /*size of soliton shape*/ #define l (int)(s+1) /*array length for soliton*/ #define N (int)2000 /*length of field array--lattice sites*/ #define Pi (double)4*atan(1) #define buff (int)50 double shoot(double Sol[N],double A,double c); double bisect(double A0,double A1,double Sol[N],double tol,double c); void super_pos(double antiSol[N],double Sol[N],double phi[][N]); void vel_ver(double phi[][N],double v,double c,int tsteps,double dt); int main(int argc, char **argv) { double c,Sol[N],antiSol[N],A,A0,A1,tol,v,dt; int tsteps,i; FILE *fp1,*fp2,*fp3; fp1 = fopen("soliton.dat","w"); fp2 = fopen("final-phi.dat","w"); fp3 = fopen("energy.dat","w"); printf("Please input the number of time steps:"); scanf("%d",&tsteps); printf("Also, enter the time step size:"); scanf("%lf",&dt); do{ printf("Please input the parameter c in the interval [-1/3,1]:"); scanf("%lf",&c);} while(c < (-1./3.) || c > 1.); printf("Please input the inital speed of eiter soliton:"); scanf("%lf",&v); double phi[tsteps+1][N]; tol = 0.0000001; A0 = 0.; A1 = 2.*Pi; A = bisect(A0,A1,Sol,tol,c); shoot(Sol,A,c); for (i=0;i<N;i++) { fprintf(fp1,"%d\t",i); fprintf(fp1,"%lf\n",Sol[i]); } fclose(fp1); super_pos(antiSol,Sol,phi); /*vel_ver(phi,v,c,tsteps,dt); for (i=0;i<N;i++){ fprintf(fp2,"%d\t",i); fprintf(fp2,"%lf\n",phi[tsteps][i]); }*/ } double shoot(double Sol[N],double A,double c) { int i,j; /*Initial Conditions*/ for (i=0;i<buff;i++) { Sol[i] = 0.; } for (i=buff+l;i<N;i++) { Sol[i] = 2.*Pi; } Sol[buff]= 0; Sol[buff+1]= A*exp(sqrt(1+3*c)*dx); for (i=buff+2;i<buff+l;i++) { Sol[i] = (dx*dx)*( sin(Sol[i-1]) + c*sin(3.*(Sol[i-1])) ) - Sol[i-2] + 2.*Sol[i-1]; } return Sol[i-1]; } double bisect(double A0,double A1,double Sol[N],double tol,double c) { double Amid,shot; while (A1-A0 > tol) { Amid = 0.5*(A0+A1); shot = shoot(Sol, Amid, c); if (shot==2.*Pi) { return Amid; } if (shot > 2.*Pi){ A1 = Amid; } else if (shot < 2.*Pi){ A0 = Amid; } } return 0.5*(A1+A0); } void super_pos(double antiSol[N],double Sol[N],double phi[][N]) { int i; /*for (i=0;i<N;i++) { phi[i]=0; } for (i=buffer+s;i<1950-s;i++) { phi[i]=2*Pi; }*/ for (i=0;i<N;i++) { antiSol[i] = Sol[N-i]; } /*for (i=0;i<s+1;i++) { phi[buffer+j] = Sol[j]; phi[1549+j] = antiSol[j]; }*/ for (i=0;i<N;i++) { phi[0][i] = antiSol[i] + Sol[i] - 2.*Pi; } } /* This funciton will set the 2nd input array to the derivative at the time t, for all points x in the lattice */ void deriv2(double phi[][N],double DphiDx2[][N],int t) { //double SolDer2[s+1]; int x; for (x=0;x<N;x++) { DphiDx2[t][x] = (phi[buff+x+1][t] + phi[buff+x-1][t] - 2.*phi[x][t])/(dx*dx); } /*for (i=0;i<N;i++) { ptr[i] = &SolDer2[i]; }*/ //return DphiDx2[x]; } void vel_ver(double phi[][N],double v,double c,int tsteps,double dt) { int t,x; double d1,d2,dp,DphiDx1[tsteps+1][N],DphiDx2[tsteps+1][N],dpdt[tsteps+1][N],p[tsteps+1][N]; for (t=0;t<tsteps;t++){ if (t==0){ for (x=0;x<N;x++){//inital conditions deriv2(phi,DphiDx2,t); dpdt[t][x] = DphiDx2[t][x] - sin(phi[t][x]) - sin(3.*phi[t][x]); DphiDx1[t][x] = (phi[t][x+1] - phi[t][x])/dx; p[t][x] = -v*DphiDx1[t][x]; } } for (x=0;x<N;x++){//velocity-verlet phi[t+1][x] = phi[t][x] + dt*p[t][x] + (dt*dt/2)*dpdt[t][x]; p[t+1][x] = p[t][x] + (dt/2)*dpdt[t][x]; deriv2(phi,DphiDx2,t+1); dpdt[t][x] = DphiDx2[t][x] - sin(phi[t+1][x]) - sin(3.*phi[t+1][x]); p[t+1][x] += (dt/2)*dpdt[t+1][x]; } } } So, this really isn't due to my overwriting the end of the Sol array. I've commented out both functions that I suspected of causing the problem (bisect or shoot) and inserted a print function. Two things happen. When I have code like below: double A,Pi,B,c; c=0; Pi = 4.*atan(1.); A = Pi; B = 1./4.; printf("%lf",B); B = shoot(Sol,A,c); printf("%lf",B); I get a segfault from the function, shoot. However, if I take away the shoot function so that I have: double A,Pi,B,c; c=0; Pi = 4.*atan(1.); A = Pi; B = 1./4.; printf("%lf",B); it gives me a segfault at the printf... Why!?

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  • Cann Boost Program_options separate comma separated argument values

    - by lrm
    If my command line is: > prog --mylist=a,b,c Can Boost's program_options be setup to see three distinct argument values for the mylist argument? I have configured program_options as: namespace po = boost::program_options; po::options_description opts("blah") opts.add_options() ("mylist", std::vector<std::string>>()->multitoken, "description"); po::variables_map vm; po::store(po::parse_command_line(argc, argv, opts), vm); po::notify(vm); When I check the value of the mylist argument, I see one value as a,b,c. I'd like to see three distinct values, split on comma. This works fine if I specify the command line as: > prog --mylist=a b c or > prog --mylist=a --mylist=b --mylist=c Is there a way to configure program_options so that it sees a,b,c as three values that should each be inserted into the vector, rather than one? I am using boost 1.41, g++ 4.5.0 20100520, and have enabled c++0x experimental extensions.

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  • Programming style: should you return early if a guard condition is not satisfied?

    - by John Topley
    One thing I've sometimes wondered is which is the better style out of the two shown below (if any)? Is it better to return immediately if a guard condition hasn't been satisfied, or should you only do the other stuff if the guard condition is satisfied? For the sake of argument, please assume that the guard condition is a simple test that returns a boolean, such as checking to see if an element is in a collection, rather than something that might affect the control flow by throwing an exception. // Style 1 public SomeType aMethod() { SomeType result = null; if (!guardCondition()) { return result; } doStuffToResult(result); doMoreStuffToResult(result); return result; } // Style 2 public SomeType aMethod() { SomeType result = null; if (guardCondition()) { doStuffToResult(result); doMoreStuffToResult(result); } return result; }

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  • How to synchronize cuda threads when they are in the same loop and we need to synchronize them to ex

    - by Vickey
    Hi all, I have written a code and Now I want to implement this on cuda GPU but I'm new to synchronization so please help me with this, It's little urgent to me. Below I'm presenting the code and I want to that LOOP1 to be executed by all threads (heance I want to this portion to take advantage of cuda and the remaining portion (the portion other from the LOOP1) is to be executed by only a single thread. do{ point_set = master_Q[(*num_mas) - 1].q; List* temp = point_set; List* pa = point_set; if(master_Q[num_mas[0] - 1].max) max_level = (int) (ceilf(il2 * log(master_Q[num_mas[0] - 1].max))); *num_mas = (*num_mas) - 1; while(point_set){ List* insert_ele = temp; while(temp){ insert_ele = temp; if((insert_ele->dist[insert_ele->dist_index-1] <= pow(2, max_level-1)) || (top_level == max_level)){ if(point_set == temp){ point_set = temp->next; pa = temp->next; } else{ pa->next = temp->next; } temp = NULL; List* new_point_set = point_set; float maximum_dist = 0; if(parent->p_index != insert_ele->point_index){ List* tmp = new_point_set; float *b = &(data[(insert_ele->point_index)*point_len]); **LOOP 1:** while(tmp){ float *c = &(data[(tmp->point_index)*point_len]); float sum = 0.; for(int j = 0; j < point_len; j+=2){ float d1 = b[j] - c[j]; float d2 = b[j+1] - c[j+1]; d1 *= d1; d2 *= d2; sum = sum + d1 + d2; } tmp->dist[tmp->dist_index] = sqrt(sum); if(maximum_dist < tmp->dist[tmp->dist_index]) maximum_dist = tmp->dist[tmp->dist_index]; tmp->dist_index = tmp->dist_index+1; tmp = tmp->next; } max_distance = maximum_dist; } while(new_point_set || insert_ele){ List* far, *par, *tmp, *tmp_new; far = NULL; tmp = new_point_set; tmp_new = NULL; float level_dist = pow(2, max_level-1); float maxdist = 0, maxp = 0; while(tmp){ if(tmp->dist[(tmp->dist_index)-1] > level_dist){ if(maxdist < tmp->dist[tmp->dist_index-1]) maxdist = tmp->dist[tmp->dist_index-1]; if(tmp == new_point_set){ new_point_set = tmp->next; par = tmp->next; } else{ par->next = tmp->next; } if(far == NULL){ far = tmp; tmp_new = far; } else{ tmp_new->next = tmp; tmp_new = tmp; } if(parent->p_index != insert_ele->point_index) tmp->dist_index = tmp->dist_index - 1; tmp = tmp->next; tmp_new->next = NULL; } else{ par = tmp; if(maxp < tmp->dist[(tmp->dist_index)-1]) maxp = tmp->dist[(tmp->dist_index)-1]; tmp = tmp->next; } } if(0 == maxp){ tmp = new_point_set; aloc_mem[*tree_index].p_index = insert_ele->point_index; aloc_mem[*tree_index].no_child = 0; aloc_mem[*tree_index].level = max_level--; parent->children_index[parent->no_child++] = *tree_index; parent = &(aloc_mem[*tree_index]); tree_index[0] = tree_index[0]+1; while(tmp){ aloc_mem[*tree_index].p_index = tmp->point_index; aloc_mem[(*tree_index)].no_child = 0; aloc_mem[(*tree_index)].level = master_Q[(*cur_count_Q)-1].level; parent->children_index[parent->no_child] = *tree_index; parent->no_child = parent->no_child + 1; (*tree_index)++; tmp = tmp->next; } cur_count_Q[0] = cur_count_Q[0]-1; new_point_set = NULL; } master_Q[*num_mas].q = far; master_Q[*num_mas].parent = parent; master_Q[*num_mas].valid = true; master_Q[*num_mas].max = maxdist; master_Q[*num_mas].level = max_level; num_mas[0] = num_mas[0]+1; if(0 != maxp){ aloc_mem[*tree_index].p_index = insert_ele->point_index; aloc_mem[*tree_index].no_child = 0; aloc_mem[*tree_index].level = max_level; parent->children_index[parent->no_child++] = *tree_index; parent = &(aloc_mem[*tree_index]); tree_index[0] = tree_index[0]+1; if(maxp){ int new_level = ((int) (ceilf(il2 * log(maxp)))) +1; if (new_level < (max_level-1)) max_level = new_level; else max_level--; } else max_level--; } if( 0 == maxp ) insert_ele = NULL; } } else{ if(NULL == temp->next){ master_Q[*num_mas].q = point_set; master_Q[*num_mas].parent = parent; master_Q[*num_mas].valid = true; master_Q[*num_mas].level = max_level; num_mas[0] = num_mas[0]+1; } pa = temp; temp = temp->next; } } if((*num_mas) > 1){ List *temp2 = master_Q[(*num_mas)-1].q; while(temp2){ List* temp3 = master_Q[(*num_mas)-2].q; master_Q[(*num_mas)-2].q = temp2; if((master_Q[(*num_mas)-1].parent)->p_index != (master_Q[(*num_mas)-2].parent)->p_index){ temp2->dist_index = temp2->dist_index - 1; } temp2 = temp2->next; master_Q[(*num_mas)-2].q->next = temp3; } num_mas[0] = num_mas[0]-1; } point_set = master_Q[(*num_mas)-1].q; temp = point_set; pa = point_set; parent = master_Q[(*num_mas)-1].parent; max_level = master_Q[(*num_mas)-1].level; if(master_Q[(*num_mas)-1].max) if( max_level > ((int) (ceilf(il2 * log(master_Q[(*num_mas)-1].max)))) +1) max_level = ((int) (ceilf(il2 * log(master_Q[(*num_mas)-1].max)))) +1; num_mas[0] = num_mas[0]-1; } }while(*num_mas > 0);

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  • routing mvc on the web

    - by generic_noob
    Hi, I was wondering if anyone could possibly provide me some advice on how i could improve the routing (and/or architecture) to each 'section' of my application. (I'm writing in PHP5, and trying to use strict MVC) Basically, I have a generic index page for the app, and that will spew out boilerplate stuff like jquery and the css etc. and it also generates the main navidation for the entire site, but i'm unsure about the best approach to connect the 'main menu' items(hyperlinks) with their associated controllers. Up until now I have been appending strings into the url and using a 'switch' statement to branch to the correct controller(and view) by extracting the strings back out of '$GET[]' to let it execute the code for the corrosponding action. for instance if i had a basic crud system for customer data, the url to edit a customers details would look like 'www.example.com/index.php?page=customer&action=edit&id=4'. I'm worried that there is a security concern by doing it this way, and i'm not sure of an alternative to branch the main 'index.php' file to the correct controller for each action once the user has clicked the link. Would it be better to use mod_rewrite to disguise the controllers names? or to create a similar system to the ASP MVC framework, where there is a seperate routing system where each url is filtered to get the associated controller? Cheers!

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  • Can Boost Program_options separate comma separated argument values

    - by lrm
    If my command line is: > prog --mylist=a,b,c Can Boost's program_options be setup to see three distinct argument values for the mylist argument? I have configured program_options as: namespace po = boost::program_options; po::options_description opts("blah") opts.add_options() ("mylist", std::vector<std::string>>()->multitoken, "description"); po::variables_map vm; po::store(po::parse_command_line(argc, argv, opts), vm); po::notify(vm); When I check the value of the mylist argument, I see one value as a,b,c. I'd like to see three distinct values, split on comma. This works fine if I specify the command line as: > prog --mylist=a b c or > prog --mylist=a --mylist=b --mylist=c Is there a way to configure program_options so that it sees a,b,c as three values that should each be inserted into the vector, rather than one? I am using boost 1.41, g++ 4.5.0 20100520, and have enabled c++0x experimental extensions.

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  • Accessing the "super of this" in Java

    - by gerdemb
    This is what I'm doing now. Is there a better way to access the super class? public class SearchWidget { private void addWishlistButton() { final SearchWidget thisWidget = this; button.addClickHandler(new ClickHandler() { public void onClick(ClickEvent event) { // A better way to access the super class? // something like "this.super" ...? workWithWidget(thisWidget); } } } } I'm programming with Google Web Toolkit, but I think this is really a generic Java question.

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  • Do programmable Ethernet devices (think onboard CPU) really exist?

    - by PeterM
    I've heard from various people that programmable Ethernet cards exist and are easily available. However I have yet to be able to track down one of these mythical devices so I'm wondering if they're just that - a myth. Such a programmable card has a gigabit Ethernet interface, has a programmable CPU and connects to the host system via PCI Express. The problem area these cards address are low latency network applications where the card itself does the work and "reports back" to the operating system. Basically the card acts as a co-processor and handles all the low latency requirements on the card, thus avoiding the issues of writing low latency code in user-land - think 0.4ms - 0.5ms response times. So my question is, do these cards really exist and if so, where can I get my hands on one?

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  • How do you manually insert options into boost.Program_options?

    - by windfinder
    I have an application that uses Boost.Program_options to store and manage its configuration options. We are currently moving away from configuration files and using database loaded configuration instead. I've written an API that reads configuration options from the database by hostname and instance name. (cool!) However, as far as I can see there is no way to manually insert these options into the boost Program_options. Has anyone used this before, any ideas? The docs from boost seem to indicate the only way to get stuff in that map is by the store function, which either reads from the command line or config file (not what I want). Basically looking for a way to manually insert the DB read values in to the map.

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  • Basic View Switch Code Crashes iPhone simulator

    - by Ouija
    I've been trying to switch two views from two separate view controllers for a while and it never works, the simulator always crashes to the home screen. I'm using Xcode 3.2.5 and this is my code - SwitchViewsViewController.h #import <UIKit/UIKit.h> #import "SecondViewController.h" @interface SwitchViewsViewController : UIViewController { } -(IBAction)pushButton; @end SwitchViewsViewController.m #import "SwitchViewsViewController.h" #import "SecondViewController.h" @implementation SwitchViewsViewController -(IBAction)pushButton { SecondViewController *screen = [[SecondViewController alloc] initWithNibName:nil bundle:nil screen.modalTransitionStyle = UIModalTransitionStyleCoverVertical; [self presentModalViewController:screen animated:YES] [screen release]; } SecondViewController.h #import <UIKit/UIKit.h> @interface SecondViewController : UIViewController { } -(IBAction)pushBack; @end SecondViewController.m #import "SecondViewController.h" @implementation SecondViewController -(IBAction)pushBack{ [self dismissModalViewControllerAnimated:YES]; } In interface builder, all i've done is linked the file's owner classes and the buttons. Also made the SwitchViewsViewController load first, and not MainWindow. Everything builds but when I try to run the app it crashes and sends it to the home screen. Can anyone help me with this?

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  • How do call this symbolic code transformation ?

    - by erric
    Hi, I often cross this kind of code transformation (or even mathematical transformation) (python example, but applies to any language) I've go a function def f(x): return x I use it into another one. def g(x): return f(x)*f(x) print g(2) leads to 4 But I want to remove the functional dependency, and I change the function g into def g(f): return f*f print g( f(2) ) leads to 4 too How do you call this kind of transformation, locally turning a function into a scalar ?

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  • Program crash on deque from queue

    - by SwedishGit
    My first question asked here, so please excuse if I fail to include something... I'm working on a homework project, which basically consists of creating a "Jukebox" (importing/exporting albums from txt files, creating and "playing" a playlist, etc.). I've become stuck on one point: When "playing" the playlist, which consists of a self-made Queue, a copy of it is made from which songs are dequeued and printed out with a time delay. This appears to run fine on the first run through the program, but if the "play" option is chosen again (with the same playlist, created from a different menu option), it crashes before managing to print the first song. It also crashes if creating a new playlist, but then it manages to print some songs (seem to depend on the number of songs in the first/new playlists...) before crashing. With printouts I've been able to track the crashing down to being on the "item = n-data" call in the deque function... but can't get my head around why this would crash. Below is the code I think should be relevant... let me know if there are other parts that would help if I include. Edit: The Debug Error shown on crash is: R6010 abort() has been called The method to play from the playlist: void Jukebox::playList() { if(songList.getNodes() > 0) { Queue tmpList(songList); Song tmpSong; while(tmpList.deque(tmpSong)) { clock_t temp; temp = clock () + 2 * CLOCKS_PER_SEC ; while (clock() < temp) {} } } else cout << "There are no songs in the playlist!" << endl; } Queue: // Queue.h - Projekt-uppgift // Håkan Sjölin 2014-05-31 //----------------------------------------------------------------------------- #ifndef queue_h #define queue_h #include "Song.h" using namespace std; typedef Song Item; class Node; class Queue { private: Node *first; Node *last; int nodes; public: Queue():first(nullptr),last(nullptr),nodes(0){}; ~Queue(); void enque(Item item); bool deque(Item &item); int getNodes() const { return nodes; } void empty(); }; #endif // Queue.cpp - Projekt-uppgift // Håkan Sjölin 2014-05-31 //----------------------------------------------------------------------------- #include "queue.h" using namespace std; class Node { public: Node *next; Item data; Node (Node *n, Item newData) : next(n), data(newData) {} }; //------------------------------------------------------------------------------ // Funktionsdefinitioner för klassen Queue //------------------------------------------------------------------------------ //------------------------------------------------------------------------------ // Destruktor //------------------------------------------------------------------------------ Queue::~Queue() { while(first!=0) { Node *tmp = first; first = first->next; delete tmp; } } //------------------------------------------------------------------------------ // Lägg till data sist i kön //------------------------------------------------------------------------------ void Queue::enque(Item item) { Node *pNew = new Node(0,item); if(getNodes() < 1) first = pNew; else last->next = pNew; last = pNew; nodes++; } //------------------------------------------------------------------------------ // Ta bort data först i kön //------------------------------------------------------------------------------ bool Queue::deque(Item &item) { if(getNodes() < 1) return false; //cout << "deque: test2" << endl; Node *n = first; //cout << "deque: test3" << endl; //cout << "item = " << item << endl; //cout << "first = " << first << endl; //cout << "n->data = " << n->data << endl; item = n->data; //cout << "deque: test4" << endl; first = first->next; //delete n; nodes--; if(getNodes() < 1) // Kön BLEV tom last = nullptr; return true; } //------------------------------------------------------------------------------ // Töm kön //------------------------------------------------------------------------------ void Queue::empty() { while (getNodes() > 0) { Item item; deque(item); } } //------------------------------------------------------------------------------ Song: // Song.h - Projekt-uppgift // Håkan Sjölin 2014-05-15 //----------------------------------------------------------------------------- #ifndef song_h #define song_h #include "Time.h" #include <string> #include <iostream> using namespace std; class Song { private: string title; string artist; Time length; public: Song(); Song(string pTitle, string pArtist, Time pLength); // Setfunktioner void setTitle(string pTitle); void setArtist(string pArtist); void setLength(Time pLength); // Getfunktioner string getTitle() const { return title;} string getArtist() const { return artist;} Time getLength() const { return length;} }; ostream &operator<<(ostream &os, const Song &song); istream &operator>>(istream &is, Song &song); #endif // Song.cpp - Projekt-uppgift // Håkan Sjölin 2014-05-15 //----------------------------------------------------------------------------- #include "Song.h" #include "Constants.h" #include <iostream> //------------------------------------------------------------------------------ // Definiering av Songs medlemsfunktioner //------------------------------------------------------------------------------ // Fövald konstruktor //------------------------------------------------------------------------------ Song::Song() { } //------------------------------------------------------------------------------ // Initieringskonstruktor //------------------------------------------------------------------------------ Song::Song(string pTitle, string pArtist, Time pLength) { title = pTitle; artist = pArtist; length = pLength; } //------------------------------------------------------------------------------ // Setfunktioner //------------------------------------------------------------------------------ //------------------------------------------------------------------------------ // setTitle // Ange titel //------------------------------------------------------------------------------ void Song::setTitle(string pTitle) { title = pTitle; } //------------------------------------------------------------------------------ // setArtist // Ange artist //------------------------------------------------------------------------------ void Song::setArtist(string pArtist) { artist = pArtist; } //------------------------------------------------------------------------------ // setTitle // Ange titel //------------------------------------------------------------------------------ void Song::setLength(Time pLength) { length = pLength; } //--------------------------------------------------------------------------- // Överlagring av utskriftsoperatorn //--------------------------------------------------------------------------- ostream &operator<<(ostream &os, const Song &song) { os << song.getTitle() << DELIM << song.getArtist() << DELIM << song.getLength(); return os; } //--------------------------------------------------------------------------- // Överlagring av inmatningsoperatorn //--------------------------------------------------------------------------- istream &operator>>(istream &is, Song &song) { string tmpString; Time tmpLength; getline(is, tmpString, DELIM); song.setTitle(tmpString); getline(is, tmpString, DELIM); song.setArtist(tmpString); is >> tmpLength; is.get(); song.setLength(tmpLength); return is; } //--------------------------------------------------------------------------- Album: // Album.h - Projekt-uppgift // Håkan Sjölin 2014-05-17 //----------------------------------------------------------------------------- #ifndef album_h #define album_h #include "Song.h" #include <string> #include <vector> #include <iostream> using namespace std; class Album { private: string name; vector<Song> songs; public: Album(); Album(string pNameTitle, vector<Song> pSongs); // Setfunktioner void setName(string pName); // Getfunktioner string getName() const { return name;} vector<Song> getSongs() const { return songs;} int getNumberOfSongs() const { return songs.size();} Time getTotalTime() const; void addSong(Song pSong); bool operator<(const Album &album) const; }; ostream &operator<<(ostream &os, const Album &album); istream &operator>>(istream &is, Album &album); #endif // Album.cpp - Projekt-uppgift // Håkan Sjölin 2014-05-17 //----------------------------------------------------------------------------- #include "Album.h" #include "Constants.h" #include <iostream> #include <string> //------------------------------------------------------------------------------ // Definiering av Albums medlemsfunktioner //------------------------------------------------------------------------------ // Fövald konstruktor //------------------------------------------------------------------------------ Album::Album() { } //------------------------------------------------------------------------------ // Initieringskonstruktor //------------------------------------------------------------------------------ Album::Album(string pName, vector<Song> pSongs) { name = pName; songs = pSongs; } //------------------------------------------------------------------------------ // Setfunktioner //------------------------------------------------------------------------------ //------------------------------------------------------------------------------ // setName // Ange namn //------------------------------------------------------------------------------ void Album::setName(string pName) { name = pName; } //------------------------------------------------------------------------------ // addSong // Lägg till song //------------------------------------------------------------------------------ void Album::addSong(Song pSong) { songs.push_back(pSong); } //------------------------------------------------------------------------------ // getTotalTime // Returnera total speltid //------------------------------------------------------------------------------ Time Album::getTotalTime() const { Time tTime(0,0,0); for(Song s : songs) { tTime = tTime + s.getLength(); } return tTime; } //--------------------------------------------------------------------------- // Mindre än //--------------------------------------------------------------------------- bool Album::operator<(const Album &album) const { return getTotalTime() < album.getTotalTime(); } //--------------------------------------------------------------------------- // Överlagring av utskriftsoperatorn //--------------------------------------------------------------------------- ostream &operator<<(ostream &os, const Album &album) { os << album.getName() << endl; os << album.getNumberOfSongs() << endl; for (size_t i = 0; i < album.getSongs().size(); i++) os << album.getSongs().at(i) << endl; return os; } //--------------------------------------------------------------------------- // Överlagring av inmatningsoperatorn //--------------------------------------------------------------------------- istream &operator>>(istream &is, Album &album) { string tmpString; int tmpNumberOfSongs; Song tmpSong; getline(is, tmpString); album.setName(tmpString); is >> tmpNumberOfSongs; is.get(); for (int i = 0; i < tmpNumberOfSongs; i++) { is >> tmpSong; album.addSong(tmpSong); } return is; } //--------------------------------------------------------------------------- Time: // Time.h - Projekt-uppgift // Håkan Sjölin 2014-05-15 //----------------------------------------------------------------------------- #ifndef time_h #define time_h #include <iostream> using namespace std; class Time { private: int hours; int minutes; int seconds; public: Time(); Time(int pHour, int pMinute, int pSecond); // Setfunktioner void setHour(int pHour); void setMinute(int pMinute); void setSecond(int pSecond); // Getfunktioner int getHour() const { return hours;} int getMinute() const { return minutes;} int getSecond() const { return seconds;} Time operator+(const Time &time) const; bool operator==(const Time &time) const; bool operator<(const Time &time) const; }; ostream &operator<<(ostream &os, const Time &time); istream &operator>>(istream &is, Time &Time); #endif // Time.cpp - Projekt-uppgift // Håkan Sjölin 2014-05-15 //----------------------------------------------------------------------------- #include "Time.h" #include <iostream> //------------------------------------------------------------------------------ // Definiering av Times medlemsfunktioner //------------------------------------------------------------------------------ // Fövald konstruktor //------------------------------------------------------------------------------ Time::Time() { } //------------------------------------------------------------------------------ // Initieringskonstruktor //------------------------------------------------------------------------------ Time::Time(int pHour, int pMinute, int pSecond) { setHour(pHour); setMinute(pMinute); setSecond(pSecond); } //------------------------------------------------------------------------------ // Setfunktioner //------------------------------------------------------------------------------ //------------------------------------------------------------------------------ // setHour // Ange timme //------------------------------------------------------------------------------ void Time::setHour(int pHour) { if(pHour>-1) hours = pHour; else hours = 0; } //------------------------------------------------------------------------------ // setMinute // Ange minut //------------------------------------------------------------------------------ void Time::setMinute(int pMinute) { if(pMinute < 60 && pMinute > -1) { minutes = pMinute; } else minutes = 0; } //------------------------------------------------------------------------------ // setSecond // Ange sekund //------------------------------------------------------------------------------ void Time::setSecond(int pSecond) { if(pSecond < 60 && pSecond > -1) { seconds = pSecond; } else seconds = 0; } //--------------------------------------------------------------------------- // Överlagring av utskriftsoperatorn //--------------------------------------------------------------------------- ostream &operator<<(ostream &os, const Time &time) { os << time.getHour()*3600+time.getMinute()*60+time.getSecond(); return os; } //--------------------------------------------------------------------------- // Överlagring av inmatningsoperatorn //--------------------------------------------------------------------------- istream &operator>>(istream &is, Time &time) { int tmp; is >> tmp; time.setSecond(tmp%60); time.setMinute((tmp/60)%60); time.setHour(tmp/3600); return is; } //--------------------------------------------------------------------------- // Likhet //-------------------------------------------------------------------------- bool Time::operator==(const Time &time) const { return hours == time.getHour() && minutes == time.getMinute() && seconds == time.getSecond(); } //--------------------------------------------------------------------------- // Mindre än //--------------------------------------------------------------------------- bool Time::operator<(const Time &time) const { if(hours == time.getHour()) { if(minutes == time.getMinute()) { return seconds < time.getSecond(); } else { return minutes < time.getMinute(); } } else { return hours < time.getHour(); } } //--------------------------------------------------------------------------- // Addition //--------------------------------------------------------------------------- Time Time::operator+(const Time &time) const { return Time(hours+time.getHour() + (minutes+time.getMinute() + (seconds+time.getSecond())/60)/60, (minutes+time.getMinute() + (seconds+time.getSecond())/60)%60, (seconds+time.getSecond())%60); } //--------------------------------------------------------------------------- Thanks in advance for any help! Edit2: Didn't think of including the more detailed crash info (as it didn't show in the crash pop-up, so to say). Anyway, here it is: Output: 'Jukebox.exe' (Win32): Loaded 'C:\Users\Håkan\Documents\Studier - IT\Objektbaserad programmering i C++\Inlämningsuppgifter\Projekt\Jukebox\Debug\Jukebox.exe'. Symbols loaded. 'Jukebox.exe' (Win32): Loaded 'C:\Windows\SysWOW64\ntdll.dll'. Cannot find or open the PDB file. 'Jukebox.exe' (Win32): Loaded 'C:\Windows\SysWOW64\kernel32.dll'. Cannot find or open the PDB file. 'Jukebox.exe' (Win32): Loaded 'C:\Windows\SysWOW64\KernelBase.dll'. Cannot find or open the PDB file. 'Jukebox.exe' (Win32): Loaded 'C:\Windows\SysWOW64\msvcp110d.dll'. Symbols loaded. 'Jukebox.exe' (Win32): Loaded 'C:\Windows\SysWOW64\msvcr110d.dll'. Symbols loaded. The thread 0xe50 has exited with code 0 (0x0). Unhandled exception at 0x0083630C in Jukebox.exe: 0xC0000005: Access violation reading location 0x0000003C. Call stack: > Jukebox.exe!Song::getLength() Line 27 C++ Jukebox.exe!operator<<(std::basic_ostream<char,std::char_traits<char> > & os, const Song & song) Line 59 C++ Jukebox.exe!Queue::deque(Song & item) Line 55 C++ Jukebox.exe!Jukebox::playList() Line 493 C++ Jukebox.exe!Jukebox::play() Line 385 C++ Jukebox.exe!Jukebox::run() Line 536 C++ Jukebox.exe!main() Line 547 C++ Jukebox.exe!__tmainCRTStartup() Line 536 C Jukebox.exe!mainCRTStartup() Line 377 C kernel32.dll!754d86e3() Unknown [Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll] ntdll.dll!7748bf39() Unknown ntdll.dll!7748bf0c() Unknown

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