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• pass by pointer is not working

  - by user323422

  #include"iostream" class CMessage { public:int a; CMessage(){} ~CMessage(){} }; void Testing(CMessage *f_pMessage)//l_pMessage is output parameter { f_pMessage = new CMessage(); f_pMessage->a = 1; } int main() { CMessage *l_pMessage =NULL; Testing(l_pMessage); std::cout<<l_pMessage->a;//getting l_pMessage = NULL; return 0; } when i called testing then inside testing f_pMessage is getting intialize but as ssoon as i after excuting testing function it should be store in l_Pmessage but it is showing NULL.confussed.....

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• what is the best way to have a Generic Comparer

  - by oo

  I have a lot of comparer classes where the class being compared is simply checking the name property of the object and doing a string compare. For example: public class ExerciseSorter : IComparer<Exercise> { public int Compare(Exercise x, Exercise y) { return String.Compare(x.Name, y.Name); } } public class CarSorter : IComparer<Car> { public int Compare(Car x, Car y) { return String.Compare(x.Name, y.Name); } } what is the best way to have this code generic so i dont need to write redundant code over and over again.

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• Initializing structs in C++

  - by Neil Butterworth

  As an addendum to this question, what is going on here: #include <string> using namespace std; struct A { string s; }; int main() { A a = {0}; } Obviously, you can't set a std::string to zero. Can someone provide an explanation (backed with references to the C++ Standard, please) about what is actually supposed to happen here? And then explain for example): int main() { A a = {42}; } Are either of these well-defined? Once again an embarrassing question for me - I always give my structs constructors, so the issue has never arisen before.

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• How do i get the value of the item selected in listview?

  - by user357032

  i thought i would use the position that i had int but when i click on the item in list view nothing happens. Please Help!!!! ListView d = (ListView) findViewById(R.id.apo); ArrayAdapter adapt = ArrayAdapter.createFromResource( this, R.array.algebra, android.R.layout.simple_list_item_1); d.setAdapter(adapt); d.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView parent, View view, int position, long id) { if (position == '0'){ Intent intent = new Intent(Algebra.this, Alqv.class); startActivity(intent); } if (position == '2'){ Intent intent1 = new Intent(Algebra.this, qfs.class); startActivity(intent1); } } });

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• Making Global Struct in C++ Program

  - by mosg

  Hello world! I am trying to make global structure, which will be seen from any part of the source code. I need it for my big Qt project, where some global variables needed. Here it is: 3 files (global.h, dialog.h & main.cpp). For compilation I use Visual Studio (Visual C++). global.h #ifndef GLOBAL_H_ #define GLOBAL_H_ typedef struct TNumber { int g_nNumber; } TNum; TNum Num; #endif dialog.h #ifndef DIALOG_H_ #define DIALOG_H_ #include <iostream> #include "global.h" using namespace std; class ClassB { public: ClassB() {}; void showNumber() { Num.g_nNumber = 82; cout << "[ClassB][Change Number]: " << Num.g_nNumber << endl; } }; #endif and main.cpp #include <iostream> #include "global.h" #include "dialog.h" using namespace std; class ClassA { public: ClassA() { cout << "Hello from class A!\n"; }; void showNumber() { cout << "[ClassA]: " << Num.g_nNumber << endl; } }; int main(int argc, char **argv) { ClassA ca; ClassB cb; ca.showNumber(); cb.showNumber(); ca.showNumber(); cout << "Exit.\n"; return 0; } When I`m trying to build this little application, compilation works fine, but the linker gives me back an error: 1>dialog.obj : error LNK2005: "struct TNumber Num" (?Num@@3UTNumber@@A) already defined in main.obj Is there exists any solution? Thanks.

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• Receiving broadcast packets using packet socket

  - by user314336

  Hello I try to send DHCP RENEW packets to the network and receive the responses. I broadcast the packet and I can see that it's successfully sent using Wireshark. But I have difficulties receiving the responses.I use packet sockets to catch the packets. I can see that there are responses to my RENEW packet using Wireshark, but my function 'packet_receive_renew' sometimes catch the packets but sometimes it can not catch the packets. I set the file descriptor using FDSET but the 'select' in my code can not realize that there are new packets for that file descriptor and timeout occurs. I couldn't make it clear that why it sometimes catches the packets and sometimes doesn't. Anybody have an idea? Thanks in advance. Here's the receive function. int packet_receive_renew(struct client_info* info) { int fd; struct sockaddr_ll sock, si_other; struct sockaddr_in si_me; fd_set rfds; struct timeval tv; time_t start, end; int bcast = 1; int ret = 0, try = 0; char buf[1500] = {'\0'}; uint8_t tmp[BUFLEN] = {'\0'}; struct dhcp_packet pkt; socklen_t slen = sizeof(si_other); struct dhcps* new_dhcps; memset((char *) &si_me, 0, sizeof(si_me)); memset((char *) &si_other, 0, sizeof(si_other)); memset(&pkt, 0, sizeof(struct dhcp_packet)); define SERVER_AND_CLIENT_PORTS ((67 << 16) + 68) static const struct sock_filter filter_instr[] = { /* check for udp */ BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9), BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 4), /* L5, L1, is UDP? */ /* skip IP header */ BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0), /* L5: */ /* check udp source and destination ports */ BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0), BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */ /* returns */ BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ), /* L3: pass */ BPF_STMT(BPF_RET|BPF_K, 0), /* L4: reject */ }; static const struct sock_fprog filter_prog = { .len = sizeof(filter_instr) / sizeof(filter_instr[0]), /* casting const away: */ .filter = (struct sock_filter *) filter_instr, }; printf("opening raw socket on ifindex %d\n", info->interf.if_index); if (-1==(fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)))) { perror("packet_receive_renew::socket"); return -1; } printf("got raw socket fd %d\n", fd); /* Use only if standard ports are in use */ /* Ignoring error (kernel may lack support for this) */ if (-1==setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog, sizeof(filter_prog))) perror("packet_receive_renew::setsockopt"); sock.sll_family = AF_PACKET; sock.sll_protocol = htons(ETH_P_IP); //sock.sll_pkttype = PACKET_BROADCAST; sock.sll_ifindex = info->interf.if_index; if (-1 == bind(fd, (struct sockaddr *) &sock, sizeof(sock))) { perror("packet_receive_renew::bind"); close(fd); return -3; } if (-1 == setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &bcast, sizeof(bcast))) { perror("packet_receive_renew::setsockopt"); close(fd); return -1; } FD_ZERO(&rfds); FD_SET(fd, &rfds); tv.tv_sec = TIMEOUT; tv.tv_usec = 0; ret = time(&start); if (-1 == ret) { perror("packet_receive_renew::time"); close(fd); return -1; } while(1) { ret = select(fd + 1, &rfds, NULL, NULL, &tv); time(&end); if (TOTAL_PENDING <= (end - start)) { fprintf(stderr, "End receiving\n"); break; } if (-1 == ret) { perror("packet_receive_renew::select"); close(fd); return -4; } else if (ret) { new_dhcps = (struct dhcps*)calloc(1, sizeof(struct dhcps)); if (-1 == recvfrom(fd, buf, 1500, 0, (struct sockaddr*)&si_other, &slen)) { perror("packet_receive_renew::recvfrom"); close(fd); return -4; } deref_packet((unsigned char*)buf, &pkt, info); if (-1!=(ret=get_option_val(pkt.options, DHO_DHCP_SERVER_IDENTIFIER, tmp))) { sprintf((char*)tmp, "%d.%d.%d.%d", tmp[0],tmp[1],tmp[2],tmp[3]); fprintf(stderr, "Received renew from %s\n", tmp); } else { fprintf(stderr, "Couldnt get DHO_DHCP_SERVER_IDENTIFIER%s\n", tmp); close(fd); return -5; } new_dhcps->dhcps_addr = strdup((char*)tmp); //add to list if (info->dhcps_list) info->dhcps_list->next = new_dhcps; else info->dhcps_list = new_dhcps; new_dhcps->next = NULL; } else { try++; tv.tv_sec = TOTAL_PENDING - try * TIMEOUT; tv.tv_usec = 0; fprintf(stderr, "Timeout occured\n"); } } close(fd); printf("close fd:%d\n", fd); return 0; }

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• How to retrieve XML attribute for custom control

  - by David

  I've created a combo box control with a edittext and spinner. I'm trying to let the android:prompt attribute be passed onto the spinner, which means I need to catch it in the constructor which passes my the AttributeSet and set it on the spinner. I can't figure out how to get the value of the prompt. I'm trying, int[] ra = { android.R.attr.prompt }; TypedArray ta = context.getTheme().obtainStyledAttributes(ra); int id = ta.getResourceId(0, 0); I get back 0, which means it didn't find the attribute. I also did a ta.count() which returned 0. So I'm not getting anything back. My XML simply defines an android:prompt value. Thanks

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• How to resize an openGL window created with wglCreateContext?

  - by Nick

  Is it possible to resize an openGL window (or device context) created with wglCreateContext without disabling it? If so how? Right now I have a function which resizes the DC but the only way I could get it to work was to call DisableOpenGL and then re-enable. This causes any textures and other state changes to be lost. I would like to do this without the disable so that I do not have to go through the tedious task of recreating the openGL DC state. HWND hWnd; HDC hDC; void View_setSizeWin32(int width, int height) { // resize the window LPRECT rec = malloc(sizeof(RECT)); GetWindowRect(hWnd, rec); SetWindowPos( hWnd, HWND_TOP, rec->left, rec->top, rec->left+width, rec->left+height, SWP_NOMOVE ); free(rec); // sad panda DisableOpenGL( hWnd, hDC, hRC ); EnableOpenGL( hWnd, &hDC, &hRC ); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(-(width/2), width/2, -(height/2), height/2, -1.0, 1.0); // have fun recreating the openGL state.... } void EnableOpenGL(HWND hWnd, HDC * hDC, HGLRC * hRC) { PIXELFORMATDESCRIPTOR pfd; int format; // get the device context (DC) *hDC = GetDC( hWnd ); // set the pixel format for the DC ZeroMemory( &pfd, sizeof( pfd ) ); pfd.nSize = sizeof( pfd ); pfd.nVersion = 1; pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER; pfd.iPixelType = PFD_TYPE_RGBA; pfd.cColorBits = 24; pfd.cDepthBits = 16; pfd.iLayerType = PFD_MAIN_PLANE; format = ChoosePixelFormat( *hDC, &pfd ); SetPixelFormat( *hDC, format, &pfd ); // create and enable the render context (RC) *hRC = wglCreateContext( *hDC ); wglMakeCurrent( *hDC, *hRC ); } void DisableOpenGL(HWND hWnd, HDC hDC, HGLRC hRC) { wglMakeCurrent( NULL, NULL ); wglDeleteContext( hRC ); ReleaseDC( hWnd, hDC ); }

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• Selecting random numbers iphone sdk

  - by harekam_taj

  Hey, I want to select 10 random numbers from 1 to 35. I am trying to do the following, but I get some repeated numbers int totalNumberCnt = 1; while (totalNumberCnt < 11) { int randomNumber1 = 1 + arc4random() % 35; NSString *numberString = [NSString stringWithFormat: @"%d",randomNumber1]; NSLog(numberString); [firstNumber addObject:numberString]; [secondNumber addObject:numberString]; totalNumberCnt++; } Thank you for your help.

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• Autocorrelation method for pitch determination.. whats d input data form..?

  - by harsh

  i hav read a code for pitch determination using autocorrelation method. can anybody please tell wht wud b d input data(passed as argument to DetectPitch()) function here: double DetectPitch(short* data) { int sampleRate = 2048; //Create sine wave double *buffer = malloc(1024*sizeof(short)); double amplitude = 0.25 * 32768; //0.25 * max length of short double frequency = 726.0; for (int n = 0; n < 1024; n++) { buffer[n] = (short)(amplitude * sin((2 * 3.14159265 * n * frequency) / sampleRate)); } doHighPassFilter(data); printf("Pitch from sine wave: %f\n",detectPitchCalculation(buffer, 50.0, 1000.0, 1, 1)); printf("Pitch from mic: %f\n",detectPitchCalculation(data, 50.0, 1000.0, 1, 1)); return 0; }

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• Why my print current date time (C language) gives different answer

  - by vodkhang

  I want to get the current date (day, mon and year). I found out there are some functions in C to do that like ctime (get the string of time), localtime and gmtime. I tried with following code but the output are different. I get this output: The date and time is Tue Apr 20 2010 (which is correct) The year is : 110 The year is : 110. Does anybody know why? int main(int argc, char** argv) { time_t now; if((now = time(NULL)) == (time_t)-1) { puts("Failure in getting time"); } else { printf("The date and time is: %s\n", ctime(&now)); printf("The year is: %ld\n", localtime(&now)->tm_year); printf("The year is: %ld\n", gmtime(&now)->tm_year); } getchar(); }

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• Need to get Multiple tables from SqlServer at a time

  - by narmadha

  Hi ,I am working with C#.net,I am using cursor concept in my storedprocedure,While executing it in Sqlserver it is showing Multiple tables,but it is not returning multiple Tables in the code,it is returning only the first table,The following is the code which i have used: DataSet ds = new DataSet("table1"); using (SqlConnection connection = new SqlConnection(connectionstring)) { using (SqlDataAdapter da = new SqlDataAdapter("getworkpersondetails_Orderidwise", connection)) { da.SelectCommand.CommandType = CommandType.StoredProcedure; SqlParameter param; param = new SqlParameter("@OrderId", SqlDbType.Int); param.Value = OrderId; da.SelectCommand.Parameters.Add(param); param = new SqlParameter("@CompanyId", SqlDbType.Int); param.Value = CompanyId; da.SelectCommand.Parameters.Add(param); connection.Open(); da.Fill(ds); connection.Close(); return ds; } }

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• Using Linq to select a range of members in a list

  - by clintp

  Given a list of elements like so: int[] ia = new int[] { -4, 10, 11, 12, 13, -1, 9, 8, 7, 6, 5, 4, -2, 6, 15, 32, -5, 6, 19, 22 }; Is there an easy way in Linq to do something along the lines of "Select the elements from the -1 up to the next negative number (or the list exhausts)"? A successful result for -1 would be (-1, 9, 8, 7, 6, 5, 4). Using -2 would give the result (-2, 6, 15, 32). Not a homework problem. I'm just looking at an implementation using a bool, a for loop, and an if wondering if there's a cleaner way to do it.

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• Using libgrib2c in c++ application, linker error "Undefined reference to..."

  - by Rich

  EDIT: If you're going to be doing things with GRIB files I would recommend the GDAL library which is backed by the Open Source Geospatial Foundation. You will save yourself a lot of headache :) I'm using Qt creator in Ubuntu creating a c++ app. I am attempting to use an external lib, libgrib2c.a, that has a header grib2.h. Everything compiles, but when it tries to link I get the error: undefined reference to 'seekgb(_IO_FILE*, long, long, long*, long*) I have tried wrapping the header file with: extern "C"{ #include "grib2.h" } But it didn't fix anything so I figured that was not my problem. In the .pro file I have the line: include($${ROOT}/Shared/common/commonLibs.pri) and in commonLibs.pri I have: INCLUDEPATH+=$${ROOT}/external_libs/g2clib/include LIBS+=-L$${ROOT}/external_libs/g2clib/lib LIBS+=-lgrib2c I am not encountering an error finding the library. If I do a nm command on the libgrib2c.a I get: nm libgrib2c.a | grep seekgb seekgb.o: 00000000 T seekgb And when I run qmake with the additional argument of LIBS+=-Wl,--verbose I can find the lib file in the output: attempt to open /usr/lib/libgrib2c.so failed attempt to open /usr/lib/libgrib2c.a failed attempt to open /mnt/sdb1/ESMF/App/ESMF_App/../external_libs/linux/qwt_6.0.2/lib/libgrib2c.so failed attempt to open /mnt/sdb1/ESMF/App/ESMF_App/../external_libs/linux/qwt_6.0.2/lib/libgrib2c.a failed attempt to open ..//Shared/Config/lib/libgrib2c.so failed attempt to open ..//Shared/Config/lib/libgrib2c.a failed attempt to open ..//external_libs/libssh2/lib/libgrib2c.so failed attempt to open ..//external_libs/libssh2/lib/libgrib2c.a failed attempt to open ..//external_libs/openssl/lib/libgrib2c.so failed attempt to open ..//external_libs/openssl/lib/libgrib2c.a failed attempt to open ..//external_libs/g2clib/lib/libgrib2c.so failed attempt to open ..//external_libs/g2clib/lib/libgrib2c.a succeeded Although it doesn't show any of the .o files in the library is this because it is a c library in my c++ app? in the .cpp file that I am trying to use the library I have: #include "gribreader.h" #include <stdio.h> #include <stdlib.h> #include <external_libs/g2clib/include/grib2.h> #include <Shared/logging/Logger.hpp> //------------------------------------------------------------------------------ /// Opens a GRIB file from disk. /// /// This function opens the grib file and searches through it for how many GRIB /// messages are contained as well as their starting locations. /// /// \param a_filePath. The path to the file to be opened. /// \return True if successful, false if not. //------------------------------------------------------------------------------ bool GRIBReader::OpenGRIB(std::string a_filePath) { LOG(notification)<<"Attempting to open grib file: "<< a_filePath; if(isOpen()) { CloseGRIB(); } m_filePath = a_filePath; m_filePtr = fopen(a_filePath.c_str(), "r"); if(m_filePtr == NULL) { LOG(error)<<"Unable to open file: " << a_filePath; return false; } LOG(notification)<<"Successfully opened GRIB file"; g2int currentMessageSize(1); g2int seekPosition(0); g2int lengthToBeginningOfGrib(0); g2int seekLength(32000); int i(0); int iterationLimit(300); m_GRIBMessageLocations.clear(); m_GRIBMessageSizes.clear(); while(i < iterationLimit) { seekgb(m_filePtr, seekPosition, seekLength, &lengthToBeginningOfGrib, &currentMessageSize); if(currentMessageSize != 0) { LOG(verbose) << "Adding GRIB message location " << lengthToBeginningOfGrib << " with length " << currentMessageSize; m_GRIBMessageLocations.push_back(lengthToBeginningOfGrib); m_GRIBMessageSizes.push_back(currentMessageSize); seekPosition = lengthToBeginningOfGrib + currentMessageSize; LOG(verbose) << "GRIB seek position moved to " << seekPosition; } else { LOG(notification)<<"End of GRIB file found, after "<< i << " GRIB messages."; break; } } if(i >= iterationLimit) { LOG(warning) << "The iteration limit of " << iterationLimit << "was reached while searching for GRIB messages"; } return true; } And the header grib2.h is as follows: #ifndef _grib2_H #define _grib2_H #include<stdio.h> #define G2_VERSION "g2clib-1.4.0" #ifdef __64BIT__ typedef int g2int; typedef unsigned int g2intu; #else typedef long g2int; typedef unsigned long g2intu; #endif typedef float g2float; struct gtemplate { g2int type; /* 3=Grid Defintion Template. */ /* 4=Product Defintion Template. */ /* 5=Data Representation Template. */ g2int num; /* template number. */ g2int maplen; /* number of entries in the static part */ /* of the template. */ g2int *map; /* num of octets of each entry in the */ /* static part of the template. */ g2int needext; /* indicates whether or not the template needs */ /* to be extended. */ g2int extlen; /* number of entries in the template extension. */ g2int *ext; /* num of octets of each entry in the extension */ /* part of the template. */ }; typedef struct gtemplate gtemplate; struct gribfield { g2int version,discipline; g2int *idsect; g2int idsectlen; unsigned char *local; g2int locallen; g2int ifldnum; g2int griddef,ngrdpts; g2int numoct_opt,interp_opt,num_opt; g2int *list_opt; g2int igdtnum,igdtlen; g2int *igdtmpl; g2int ipdtnum,ipdtlen; g2int *ipdtmpl; g2int num_coord; g2float *coord_list; g2int ndpts,idrtnum,idrtlen; g2int *idrtmpl; g2int unpacked; g2int expanded; g2int ibmap; g2int *bmap; g2float *fld; }; typedef struct gribfield gribfield; /* Prototypes for unpacking API */ void seekgb(FILE *,g2int ,g2int ,g2int *,g2int *); g2int g2_info(unsigned char *,g2int *,g2int *,g2int *,g2int *); g2int g2_getfld(unsigned char *,g2int ,g2int ,g2int ,gribfield **); void g2_free(gribfield *); /* Prototypes for packing API */ g2int g2_create(unsigned char *,g2int *,g2int *); g2int g2_addlocal(unsigned char *,unsigned char *,g2int ); g2int g2_addgrid(unsigned char *,g2int *,g2int *,g2int *,g2int ); g2int g2_addfield(unsigned char *,g2int ,g2int *, g2float *,g2int ,g2int ,g2int *, g2float *,g2int ,g2int ,g2int *); g2int g2_gribend(unsigned char *); /* Prototypes for supporting routines */ extern double int_power(double, g2int ); extern void mkieee(g2float *,g2int *,g2int); void rdieee(g2int *,g2float *,g2int ); extern gtemplate *getpdstemplate(g2int); extern gtemplate *extpdstemplate(g2int,g2int *); extern gtemplate *getdrstemplate(g2int); extern gtemplate *extdrstemplate(g2int,g2int *); extern gtemplate *getgridtemplate(g2int); extern gtemplate *extgridtemplate(g2int,g2int *); extern void simpack(g2float *,g2int,g2int *,unsigned char *,g2int *); extern void compack(g2float *,g2int,g2int,g2int *,unsigned char *,g2int *); void misspack(g2float *,g2int ,g2int ,g2int *, unsigned char *, g2int *); void gbit(unsigned char *,g2int *,g2int ,g2int ); void sbit(unsigned char *,g2int *,g2int ,g2int ); void gbits(unsigned char *,g2int *,g2int ,g2int ,g2int ,g2int ); void sbits(unsigned char *,g2int *,g2int ,g2int ,g2int ,g2int ); int pack_gp(g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *); #endif /* _grib2_H */ I have been scratching my head for two days on this. If anyone has an idea on what to do or can point me in some sort of direction, I'm stumped. Also, if you have any comments on how I can improve this post I'd love to hear them, kinda new at this posting thing. Usually I'm able to find an answer in the vast stores of knowledge already contained on the web.

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• java - how to split string in to multiple parts?

  - by Ewen

  I have a string that contains a value "firstword second third", and an ArrayList. I want to split the whole string in to by spaces and add the splitted strings in to the ArrayList. For example,"firstword second third" can be split to three separate strings and added three times in to the ArrayList. "1 2 3 4" can be splitted in to 4 strings and added 4 times in to the ArrayList. See the code below: public void separateAndAdd(String notseparated) { for(int i=0;i<canBeSepartedinto(notseparated);i++{ //what should i put here in order to split the string via spaces? thearray.add(separatedstring); } } public int canBeSeparatedinto(String string) //what do i put here to find out the amount of spaces inside the string? return .... } Please leave a comment if you dont get what I mean or I should fix some errors in this post. Thanks for your time!

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• How do you write an idiomatic Scala Quicksort function?

  - by Don Mackenzie

  I recently answered a question with an attempt at writing a quicksort function in scala, I'd seen something like the code below written somewhere. def qsort(l: List[Int]): List[Int] = { l match { case Nil => Nil case pivot::tail => qsort(tail.filter(_ < pivot)) ::: pivot :: qsort(tail.filter(_ >= pivot)) } } My answer received some constructive criticism pointing out that List was a poor choice of collection for quicksort and secondly that the above wasn't tail recursive. I tried to re-write the above in a tail recursive manner but didn't have much luck. Is it possible to write a tail recursive quicksort? or, if not, how can it be done in a functional style? Also what can be done to maximise the efficiency of the implementation? Thanks in advance.

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• Java - Array's length property

  - by The New Idiot

  We can determine the length of an ArrayList<E> using its public method size() , like ArrayList<Integer> arr = new ArrayList(10); int size = arr.size(); Similarly we can determine the length of an Array object using the length property String[] str = new String[10]; int size = str.length; Whereas the size() method of ArrayList is defined inside the ArrayList class , where is this length property of Array defined ? Is it implemented by JVM or does it reside in any Java API class file ?

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• What classes should I map against with NHibernate?

  - by apollodude217

  Currently, we use NHibernate to map business objects to database tables. Said business objects enforce business rules: The set accessors will throw an exception on the spot if the contract for that property is violated. Also, the properties enforce relationships with other objects (sometimes bidirectional!). Well, whenever NHibernate loads an object from the database (e.g. when ISession.Get(id) is called), the set accessors of the mapped properties are used to put the data into the object. What's good is that the middle tier of the application enforces business logic. What's bad is that the database does not. Sometimes crap finds its way into the database. If crap is loaded into the application, it bails (throws an exception). Sometimes it clearly should bail because it cannot do anything, but what if it can continue working? E.g., an admin tool that gathers real-time reports runs a high risk of failing unnecessarily instead of allowing an admin to even fix a (potential) problem. I don't have an example on me right now, but in some instances, letting NHibernate use the "front door" properties that also enforce relationships (especially bidi) leads to bugs. What are the best solutions? Currently, I will, on a per-property basis, create a "back door" just for NHibernate: public virtual int Blah {get {return _Blah;} set {/*enforces BR's*/}} protected virtual int _Blah {get {return blah;} set {blah = value;}} private int blah; I showed the above in C# 2 (no default properties) to demonstrate how this gets us basically 3 layers of, or views, to blah!!! While this certainly works, it does not seem ideal as it requires the BL to provide one (public) interface for the app-at-large, and another (protected) interface for the data access layer. There is an additional problem: To my knowledge, NHibernate does not give you a way to distinguish between the name of the property in the BL and the name of the property in the entity model (i.e. the name you use when you query, e.g. via HQL--whenever you give NHibernate the name (string) of a property). This becomes a problem when, at first, the BR's for some property Blah are no problem, so you refer to it in your O/R mapping... but then later, you have to add some BR's that do become a problem, so then you have to change your O/R mapping to use a new _Blah property, which breaks all existing queries using "Blah" (common problem with programming against strings). Has anyone solved these problems?!

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• Java Prepared Statement Error

  - by Suresh S

  Hi Guys the following code throws me an error i have an insert statement created once and in the while loop i am dynamically setting parameter , and at the end i says ps2.addBatch() again while ( (eachLine = in.readLine()) != null)) { for (int k=stat; k <=45;k++) { ps2.setString (k,main[(k-2)]); } stat=45; for (int l=1;l<= 2; l++) { ps2.setString((stat+l),pdp[(l-1)]);// Exception } ps2.addBatch(); } This is the error java.lang.ArrayIndexOutOfBoundsException: 45 at oracle.jdbc.dbaccess.DBDataSetImpl._getDBItem(DBDataSetImpl.java:378) at oracle.jdbc.dbaccess.DBDataSetImpl._createOrGetDBItem(DBDataSetImpl.java:781) at oracle.jdbc.dbaccess.DBDataSetImpl.setBytesBindItem(DBDataSetImpl.java:2450) at oracle.jdbc.driver.OraclePreparedStatement.setItem(OraclePreparedStatement.java:1155) at oracle.jdbc.driver.OraclePreparedStatement.setString(OraclePreparedStatement.java:1572) at Processor.main(Processor.java:233)

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• How To? Use an Expression Tree to call a Generic Method when the Type is only known at runtime.

  - by David Williams

  Please bear with me; I am very new to expression trees and lambda expressions, but trying to learn. This is something that I solved using reflection, but would like to see how to do it using expression trees. I have a generic function: private void DoSomeThing<T>( param object[] args ) { // Some work is done here. } that I need to call from else where in my class. Now, normally, this would be be simple: DoSomeThing<int>( blah ); but only if I know, at design time that I am working with an int. When I do not know the type until runtime is where I need the help. Like I said, I know how to do it via reflection, but I would like to do it via expression trees, as my (very limited) understanding is that I can do so. Any suggestions or points to sites where I can get this understanding, preferably with sample code?

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• Dictionary.ContainsKey return False, but a want True

  - by SkyN

  namespace Dic { public class Key { string name; public Key(string n) { name = n; } } class Program { static string Test() { Key a = new Key("A"); Key b = new Key("A"); System.Collections.Generic.Dictionary<Key, int> d = new System.Collections.Generic.Dictionary<Key, int>(); d.Add(a, 1); return d.ContainsKey(b).ToString(); } static void Main(string[] args) { System.Console.WriteLine(Test()); } } } I want TRUE!!!

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• JScrollPane content to image

  - by Sebastian Ikaros Rizzo

  I'm trying to save the main viewport and headers of a JScrollPane (larger than screen) to PNG image files. I created 3 classes extending JPanel (MainTablePanel, MapsHeaderPanel and ItemsHeaderPanel) and set them to the viewports. Each of them has this method: public BufferedImage createImage() { BufferedImage bi = new BufferedImage(getSize().width, getSize().height, BufferedImage.TYPE_INT_ARGB); Graphics g = bi.createGraphics(); paint(g); g.dispose(); return bi; } Each class has also a paint method, which paints the background and then call the super.paint() to paint some label. For example: public void paint(Graphics g){ g.setColor(Color.BLACK); g.fillRect(0, 0, getWidth(), getHeight()); g.setColor(new Color(255, 255, 0, 50)); // for loop that paints some vertical yellow lines for(int i=0; i<getWidth(); i+=K.mW){ g.fillRect(i-1, 0, 2, getHeight()); if(i%(K.mW*5)==0){ g.fillRect(i-2, 0, 4, getHeight()); } } // called to pain some rotated JLabels super.paint(g); } From an external JFrame I then tried to save them to PNG file, using this code: BufferedImage tableImg = mainTableP.createImage(); BufferedImage topImg = mapsHeaderP.createImage(); BufferedImage leftImg = itemsHeaderP.createImage(); ImageIO.write(tableImg, "png", new File(s.homeDir+"/table.png")); ImageIO.write(topImg, "png", new File(s.homeDir+"/top.png")); ImageIO.write(leftImg, "png", new File(s.homeDir+"/left.png")); This is a screenshot of the application running: screenshot And this is the header exported: top If I comment the "super.paint(g)" instruction, I obtain a correct image (thus without all JLables, clearly). It seems like the second paint (super.paint(g)) is painted shifted into the BufferedImage and taking elements outside its JPanel. Somebody could explain me this behaviour? Thank you. ========== EDIT for SSCCE ==================================== This should compile. You can execute it as it is, and in c:\ you'll find two images (top.png and left.png) that should be the same as the two headers. Unfortunately, they are not. Background is not painted. Moreover (especially if you look at left.png) you can see that the labels are painted twice and shifted (note, for example, "Left test 21"). import java.awt.*; import java.awt.image.BufferedImage; import java.io.File; import javax.imageio.ImageIO; import javax.swing.*; public class Main { public static void main(String[] args) { JFrame frame = new JFrame(); frame.setLayout(null); frame.setSize(800, 600); JScrollPane scrollP = new JScrollPane(); scrollP.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); scrollP.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); MyPanel top = new MyPanel(); for(int i=0; i<30; i++){ JLabel label = new JLabel("Test "+i); label.setOpaque(false); label.setBounds(50*i, 40, 50, 20); label.setForeground(Color.GREEN); top.add(label); } top.setLayout(null); top.setOpaque(false); top.setPreferredSize(new Dimension(50*30, 200)); top.validate(); MyPanel left = new MyPanel(); for(int i=0; i<30; i++){ JLabel label = new JLabel("Left test "+i); label.setBounds(0, 50*i, 100, 20); label.setForeground(Color.RED); left.add(label); } left.setLayout(null); left.setOpaque(false); left.setPreferredSize(new Dimension(200, 50*30)); MyPanel center = new MyPanel(); center.setLayout(null); center.setOpaque(false); center.setPreferredSize(new Dimension(50*30, 50*30)); scrollP.setViewportView(center); scrollP.setColumnHeaderView(top); scrollP.setRowHeaderView(left); scrollP.setBounds(0, 50, 750, 500); frame.add(scrollP); frame.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); frame.setVisible(true); try{ BufferedImage topImg = top.createImage(); ImageIO.write(topImg, "png", new File("C:/top.png")); BufferedImage leftImg = left.createImage(); ImageIO.write(leftImg, "png", new File("C:/left.png")); }catch(Exception e){ e.printStackTrace(); } } } class MyPanel extends JPanel{ public void paint(Graphics g){ g.setColor(Color.BLACK); g.fillRect(0, 0, getWidth(), getHeight()); g.setColor(new Color(255, 255, 0, 50)); for(int i=0; i<getWidth(); i+=50){ g.fillRect(i-1, 0, 2, getHeight()); } super.paint(g); // COMMENT this line to obtain background images } public BufferedImage createImage() { BufferedImage bi = new BufferedImage(getSize().width, getSize().height, BufferedImage.TYPE_INT_ARGB); Graphics g = bi.createGraphics(); paint(g); g.dispose(); return bi; } }

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• In Python, how to use a C++ function which returns an allocated array of structs via a ** parameter?

  - by Jon-Eric

  I'd like to use some existing C++ code, NvTriStrip, in a Python tool. SWIG easily handles the functions with simple parameters, but the main function, GenerateStrips, is much more complicated. What do I need to put in the SWIG interface file to indicate that primGroups is really an output parameter and that it must be cleaned up with delete[]? /////////////////////////////////////////////////////////////////////////// // GenerateStrips() // // in_indices: input index list, the indices you would use to render // in_numIndices: number of entries in in_indices // primGroups: array of optimized/stripified PrimitiveGroups // numGroups: number of groups returned // // Be sure to call delete[] on the returned primGroups to avoid leaking mem // bool GenerateStrips( const unsigned short* in_indices, const unsigned int in_numIndices, PrimitiveGroup** primGroups, unsigned short* numGroups, bool validateEnabled = false ); FYI, here is the PrimitiveGroup declaration: enum PrimType { PT_LIST, PT_STRIP, PT_FAN }; struct PrimitiveGroup { PrimType type; unsigned int numIndices; unsigned short* indices; PrimitiveGroup() : type(PT_STRIP), numIndices(0), indices(NULL) {} ~PrimitiveGroup() { if(indices) delete[] indices; indices = NULL; } };

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• When using a HiLo ID generation strategy, what types should be used to hold Ids?

  - by UpTheCreek

  I'm asking this from a c#/NHibnernate perspective, but it's generally applicable. The concern is that the HiLo strategy goes though id's pretty quickly, and for example a low record-count table (Such as Users) is sharing from the same set of id's as a high record-count table (Such as comments). So you can potentially get to high numbers quicker that with other strategies. So what do people recommend? Code side: int/uint/long/ulong? DBSide: int/bigint? My feeling is to go with longs and bigingts, but would like a sanity check :)

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• understanding list[i-1] vs list[i]-1

  - by user3720527

  Hopefully this is a simple answer that I am just failing to understand. Full code is public static void mystery(int[] list) { for( int i = list.length - 1; i>1; i --) { if (list[i] > list[i - 1]) { list[i -1] = list[i] - 2; list[i]++; } } } } and lets say we are using a list of [2,3,4]. I know that it will output 2,2,5 but I am unclear how to actually work through it. I understand that the list.length is 3 here, and I understand that the for loop will only run once, but I am very unclear what happens at the list[i - 1] = list[i] - 2; area. Should it be list[2-1] = list[2] - 2? How does the two being outside the bracket effect it differently? Much thanks.

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