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  • Implementing sub fields in a PropertyGrid

    - by evolve
    Alright so my terminology when it comes to C# isn't great, so I'll attempt to explain this with a small example. If you create a class which you are using within a PropertyGrid and you have the following values: class Test { public Point example { get; set; } } This will produce a PropertyGrid which has an expandable object "example" which has fields X and Y in order to create a "Point". I'm attempting to create an object "name" which has fields "firstname" and "lastname", so I have: class Test { public Name example { get; set; } } public struct Name { public string firstname { get; set; } public string lastname { get; set; } } This however isn't working as intended. I think I need to override some method(s) in order to get this working, however since I don't really have the terminology down for PropertyGrids it is difficult for me to find a solution. Any help would be great.

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  • how to get the type of a deferred template parameter

    - by smerlin
    Is there a way to get the defered type of a class template parameter ? template <class TPtr> struct foo { typedef TPtr ptr_type; typedef ??? element_type; /* shall be the type of a deferred TPtr*/ }; so foo<const char*>::element_type results in const char, and foo<std::vector<int>::iterator_type>::element_type results in int. i am aware of that i can use the value_type typedef for c++ iterators (like std::vector<int>::iterator_type::value_type), but raw pointers havent got a value_type typedef, so i am out of luck there.

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  • Trying to reduce the speed overhead of an almost-but-not-quite-int number class

    - by Fumiyo Eda
    I have implemented a C++ class which behaves very similarly to the standard int type. The difference is that it has an additional concept of "epsilon" which represents some tiny value that is much less than 1, but greater than 0. One way to think of it is as a very wide fixed point number with 32 MSBs (the integer parts), 32 LSBs (the epsilon parts) and a huge sea of zeros in between. The following class works, but introduces a ~2x speed penalty in the overall program. (The program includes code that has nothing to do with this class, so the actual speed penalty of this class is probably much greater than 2x.) I can't paste the code that is using this class, but I can say the following: +, -, +=, <, > and >= are the only heavily used operators. Use of setEpsilon() and getInt() is extremely rare. * is also rare, and does not even need to consider the epsilon values at all. Here is the class: #include <limits> struct int32Uepsilon { typedef int32Uepsilon Self; int32Uepsilon () { _value = 0; _eps = 0; } int32Uepsilon (const int &i) { _value = i; _eps = 0; } void setEpsilon() { _eps = 1; } Self operator+(const Self &rhs) const { Self result = *this; result._value += rhs._value; result._eps += rhs._eps; return result; } Self operator-(const Self &rhs) const { Self result = *this; result._value -= rhs._value; result._eps -= rhs._eps; return result; } Self operator-( ) const { Self result = *this; result._value = -result._value; result._eps = -result._eps; return result; } Self operator*(const Self &rhs) const { return this->getInt() * rhs.getInt(); } // XXX: discards epsilon bool operator<(const Self &rhs) const { return (_value < rhs._value) || (_value == rhs._value && _eps < rhs._eps); } bool operator>(const Self &rhs) const { return (_value > rhs._value) || (_value == rhs._value && _eps > rhs._eps); } bool operator>=(const Self &rhs) const { return (_value >= rhs._value) || (_value == rhs._value && _eps >= rhs._eps); } Self &operator+=(const Self &rhs) { this->_value += rhs._value; this->_eps += rhs._eps; return *this; } Self &operator-=(const Self &rhs) { this->_value -= rhs._value; this->_eps -= rhs._eps; return *this; } int getInt() const { return(_value); } private: int _value; int _eps; }; namespace std { template<> struct numeric_limits<int32Uepsilon> { static const bool is_signed = true; static int max() { return 2147483647; } } }; The code above works, but it is quite slow. Does anyone have any ideas on how to improve performance? There are a few hints/details I can give that might be helpful: 32 bits are definitely insufficient to hold both _value and _eps. In practice, up to 24 ~ 28 bits of _value are used and up to 20 bits of _eps are used. I could not measure a significant performance difference between using int32_t and int64_t, so memory overhead itself is probably not the problem here. Saturating addition/subtraction on _eps would be cool, but isn't really necessary. Note that the signs of _value and _eps are not necessarily the same! This broke my first attempt at speeding this class up. Inline assembly is no problem, so long as it works with GCC on a Core i7 system running Linux!

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  • does mysql stored procedures support data types like array, hash,etc?

    - by Yang
    i am creating a mysql function which takes in a varchar and change it to a int based on a mapping table. select name, convert_to_code(country) from users where sex = 'male' here, the convert_to_code() function takes in a country name (e.g. Japan, Finland..) and change it to country code which is an integer (e.g. 1001, 2310..) based on a mapping table called country_maping like below: country_name (varchar) | country_code (int) Japan | 1001 Finland | 2310 Canada | 8756 currently, the stored function need to select country_code from country_mapping where country_name = country_name and return the query result. is that possible to create a hash data struct in SP to optimize the process so that it will not need to perform the query for each row matches the where clause. thanks in advance!

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  • design using a readonly class in c#

    - by edosoft
    Hi Small design question here. I'm trying to develop a calculation app in C#. I have a class, let's call it InputRecord, which holds 100s of fields (multi dimensional arrays) This InputRecordclass will be used in a number of CalculationEngines. Each CalculcationEngine can make changes to a number of fields in the InputRecord. These changes are steps needed for it's calculation. Now I don't want the local changes made to the InputRecord to be used in other CalculcationEngine's classes. The first solution that comes to mind is using a struct: these are value types. However I'd like to use inheritance: each CalculationEngine needs a few fields only relevant to that engine: it's has it's own InputRecord, based on BaseInputRecord. Can anyone point me to a design that will help me accomplish this?

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  • Threading and pcap issues.

    - by cftmon
    I have a GUI program that allows a user a scan a network, the issue is that when the pcap_loop function is called, my GUI program becomes unresponsive.(the pcap_loop blocks the current thread). When i try to use pthreads, i got a SIGSEGV fault at the pcap_loop function.Why?It's as if the thread can't see the procPacket function itself. void procPacket(u_char *arg, const struct pcap_pkthdr *pkthdr, const u_char *packet) { //show packets here } void* pcapLooper(void* param) { pcap_t* handler = (pcap_t*) param; pcap_loop(handler, 900 ,procPacket, NULL ); } //some function that runs when a button is pressed //handler has been opened through pcap_open_live pthread_t scanner; int t = pthread_create(&scanner,NULL,&pcapLooper, &handler ); if(t) { std::cout << "failed" << std::endl; } pthread_join(scanner,NULL); //do other stuff.

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  • Problem with array of elements of a structure type

    - by kobac
    I'm writing an app in Visual Studio C++ and I have problem with assigning values to the elements of the array, which is array of elements of structure type. Compiler is reporting syntax error for the assigning part of the code. Is it possible in anyway to assign elements of array which are of structure type? typedef struct { CString x; double y; } Point; Point p[3]; p[0] = {"first", 10.0}; p[1] = {"second", 20.0}; p[2] = {"third", 30.0};

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  • How to share a variable between two classes?

    - by Altefquatre
    How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it?

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  • Comparison of collection datatypes in C#

    - by Joel in Gö
    Does anyone know of a good overview of the different C# collection types? I am looking for something showing which basic operations such as Add, Remove, RemoveLast etc. are supported, and giving the relative performance. It would be particularly interesting for the various generic classes - and even better if it showed eg. if there is a difference in performance between a List<T> where T is a class and one where T is a struct. A start would be a nice cheat-sheet for the abstract data structures, comparing Linked Lists, Hash Tables etc. etc. Thanks!

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  • Receving multiple multicast feeds on the same port - C, Linux

    - by Gigi
    I have an application that is receiving data from multiple multicast sources on the same port. I am able to receive the data. However, I am trying to account for statistics of each group (i.e. msgs received, bytes received) and all the data is getting mixed up. Does anyone know how to solved this problem? If I try to look at the sender's address, it is not the multicast address, but rather the IP of the sending machine. I am using the following socket options: struct ip_mreq mreq; mreq.imr_multiaddr.s_addr = inet_addr("224.1.2.3"); mreq.imr_interface.s_addr = INADDR_ANY; setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)); and also: setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &reuse, sizeof(reuse)); I appreciate any help!!!

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  • Does malloc() allocate a contiguous block of memory?

    - by user66854
    I have a piece of code written by a very old school programmer :-) . it goes something like this typedef struct ts_request { ts_request_buffer_header_def header; char package[1]; } ts_request_def; ts_request_buffer_def* request_buffer = malloc(sizeof(ts_request_def) + (2 * 1024 * 1024)); the programmer basically is working on a buffer overflow concept. I know the code looks dodgy. so my questions are: Does malloc always allocate contiguous block of memory ?. because in this code if the blocks are not contiguous , the code will fail big time Doing free(request_buffer) , will it free all the bytes allocated by malloc i.e sizeof(ts_request_def) + (2 * 1024 * 1024), or only the bytes of the size of the structure sizeof(ts_request_def) Do you see any evident problems with this approach , i need to discuss this with my boss and would like to point out any loopholes with this approach

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  • [C] converting Bit Field to int

    - by shaharg
    Hi, I have bit field declared this way: typedef struct morder { unsigned int targetRegister : 3; unsigned int targetMethodOfAddressing : 3; unsigned int originRegister : 3; unsigned int originMethodOfAddressing : 3; unsigned int oCode : 4; } bitset; I also have int array, and i want to get int value from this array, that represents the actual value of this bit field (which is actually some kind of machine word that i have the parts of it, and i want the int representation of the whole word). Thanks a lot.

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  • How to convert a function that returns a int to a function that returns a bool using boost::bind?

    - by user814628
    I have something like the following: struct A{ virtual int derp(){ if(herp()) return 1; else return 0; } void slurp(){ boost::function<bool(int x, int y> purp = /** boost bind derp to match lvalue sig **/; } } Any ideas? I want to create the function prup which basically calls derp and ignores the (x,y) passed in. I need something like bool purp(int x, int y){ return derp(); } but want to avoid creating it as a member function, and rather just create it locally if possible?

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  • C 64-bit Pointer Alignment

    - by DuneBug
    Are pointers on a 64-bit system still 4 byte aligned (similar to a double on a 32 bit system)? Or are they note 8 byte aligned? For example, on a 64-bit system how big is the following data structure: struct a { void* ptr; char myChar; } Would the pointer by 8 byte aligned, causing 7 bytes of padding for the character (total = 8 + 8 = 16)? Or would the pointer be 4 byte aligned (4 bytes + 4 bytes) causing 3 bytes of padding (total = 4 + 4 + 4 = 12)? Thanks, Ryan

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  • Glib hash table replace

    - by Robert
    I'm using GLib Hash Table. I'm trying to get the current value of the key that I found and then increment its value. I'm not quite sure how can I replace the existing value. typedef struct { gchar *key; guint my_int; } my_struct; char *v; v = g_hash_table_lookup(table, my_struct.key); if (v == NULL) g_hash_table_insert(table, g_strdup(my_struct.key), (gpointer)(my_struct.my_int)); else g_hash_table_replace() // here I'd like to do something like current_val+1 Any ideas will be appreciate it.

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  • Can this rectangle to rectangle intersection code still work?

    - by Jeremy Rudd
    I was looking for a fast performing code to test if 2 rectangles are intersecting. A search on the internet came up with this one-liner (WOOT!), but I don't understand how to write it in Javascript, it seems to be written in an ancient form of C++. Can this thing still work? Can you make it work? struct { LONG left; LONG top; LONG right; LONG bottom; } RECT; bool IntersectRect(const RECT * r1, const RECT * r2) { return ! ( r2->left > r1->right || r2->right left || r2->top > r1->bottom || r2->bottom top ); }

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  • C: getopt with list of acceptable optarg. What is the best practise ?

    - by Xavier Maillard
    Hi, I am writing a C program which is a frontend to a myriad tools. This fronted will be launched like this: my-frontend --action <AN ACTION> As all the tools have the same prefix, let say for this example this prefix is "foo". I want to concatenate "AN ACTION" to this prefix and exec this (if the tool exists). I have written something but my implementation uses strcmp to test that "AN ACTION" is a valid action. Even if this works, I do not like it. So I am looking for a nicer solution that would do the same. The list of possibilities is pretty small (less than 10) and static (the list is "hardcoded") but I am sure there is a more "C-ish" way to do this (using a struct or something like that). As I am not a C expert, I am asking for your help. Regards

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  • python list directory , subdirectory and files

    - by thomytheyon
    Hi Alls, I'm trying to make a script to list all directory, subdirectory, and files in a given directory. I tried this : import sys,os root="/home/patate/directory/" path=os.path.join(root,"targetdirectory") for r,d,f in os.walk(path): for file in f: print os.path.join(root,file) Unfortunatly it doesn't work properly, i get all the files, but not them complete path. like : if the dir struct would be : /home/patate/directory/targetdirectory/123/456/789/file.txt It would print: /home/patate/directory/targetdirectory/file.txt What i need is the first result, any help would be greatly appreciated ! Thanks

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  • Most useful Python modules from the standard library?

    - by EOL
    I am teaching a graduate level Python class at the University of Paris, and the students need to be introduced to the standard library. I want to discuss with them about some of the most important standard modules. What modules do you think are absolute musts? Even though responses probably vary depending on your field (web programming, science, etc.), I feel that some modules are commonly needed: math, sys, re, os, os.path, logging,… and maybe: collections, struct,… What modules would you suggest I present, in a 1 or 2 hour slot?

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  • How to bind a complex dictionary to a Gridview in asp.net?

    - by Mehdi
    I've used an early binding of a dictionary<string, string> to a gridview to show Urls Text and its HRef as key-value and it works like a charm. But since I want to replace the dictionary with this one : dictionary<string, LinkInfo> the binding goes wrong! Should I handle some events like as onItemDataBound or something? and the LinkInfo structure is: public struct LinkInfo{ public string href; public bool Enabled; }

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  • d2: strange lowering of protection and possible misbehavior in static imports

    - by modchan
    Consider there is moda.d: module moda; private struct modb {}; And modb.d: module modb; private import moda; And modmain.d: module modmain; static import moda; static import modb; void main() { modb v; // should NOT compile, should it? } I don't know why, but moda.modb is visible in both modmain and modb, while, as far as I understand, it should not - both due to moda being imported as static and moda.modb being private. Or should? Have I run into dmd bug or it's planned behaviour I hadn't understood?

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  • Faster way to convert from 24 bit wav pcm format to float?

    - by LMO
    I need to read data in from a wav file in 24 bit pcm format, and convert to float. I'm using Python 2.7.2. The wave package reads the data in as a string, so what I've tried is: # read in entire wav file wdata = f.readframes(nFrames) # unpack into signed integers and convert to float data = array.array('f') for i in range(0,nFrames*3,3): data.append(float(struct.unpack('<i', '\x00'+ wdata[i:i+3])[0])) # normalize sample values data = data / 0x800000 This is quite a bit faster than my earlier approaches, but still quite slow. Can anyone suggest a more efficient method?

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  • I'd like to know why a function executes fine when called from x but not when called from y

    - by Roland
    When called from archive(), readcont(char *filename) executes fine! Called from runoptions() though, it fails to list the files "archived"! why is this? The program must run in terminal. Use -h as a parameter to view the usage. This program is written to "archive" text files into ".rldzip" files. readcont( char *x) should show the files archived in file (*x) a) Successful call Use the program to archive 3 text files: rldzip.exe a.txt b.txt c.txt FILEXY -a archive() will call readcont and it will work showing the files archived after the binary FILEXY will be created. b) Unsuccessful call After the file is created, use: rldzip.exe FILEXY.rldzip -v You can see that the function crashes! I'd like to know why is this happening! /* Sa se scrie un program care: a) arhiveaza fisiere b) dezarhiveaza fisierele athivate */ #include<stdio.h> #include<stdlib.h> #include<conio.h> #include<string.h> struct content{ char *text; char *flname; }*arc; FILE *f; void readcont(char *x){ FILE *p; if((p = fopen(x, "rb")) == NULL){ perror("Critical error: "); exit(EXIT_FAILURE); } content aux; int i; fread(&i, sizeof(int), 1, p); printf("\nFiles in %s \n\n", x); while(i-- >1 && fread(&aux, sizeof(struct content), 1, p) != 0) printf("%s \n", aux.flname); fclose(p); printf("\n\n"); } void archive(int argc, char **argv){ int i; char inttext[5000], textline[1000]; //Allocate dynamic memory for the content to be archived! arc = (content*)malloc(argc * sizeof(content)); for(i=1; i< argc; i++) { if((f = fopen(argv[i], "r")) == NULL){ printf("%s: ", argv[i]); perror(""); exit(EXIT_FAILURE); } while(!feof(f)){ fgets(textline, 5000, f); strcat(inttext, textline); } arc[i-1].text = (char*)malloc(strlen(inttext) + 1); strcpy(arc[i-1].text, inttext); arc[i-1].flname = (char*)malloc(strlen(argv[i]) + 1); strcpy(arc[i-1].flname, argv[i]); fclose(f); } char *filen; filen=(char*)malloc(strlen(argv[argc])+1+7); strcpy(filen, argv[argc]); strcat(filen, ".rldzip"); f = fopen(filen, "wb"); fwrite(&argc, sizeof(int), 1, f); fwrite(arc, sizeof(content), argc, f); fclose(f); printf("Success! "); for(i=1; i< argc; i++) { (i==argc-1)? printf("and %s ", argv[i]) : printf("%s ", argv[i]); } printf("compressed into %s", filen); readcont(filen); free(filen); } void help(char *v){ printf("\n\n----------------------RLDZIP----------------------\n\nUsage: \n\n Archive n files: \n\n%s $file[1] $file[2] ... $file[n] $output -a\n\nExample:\n%s a.txt b.txt c.txt output -a\n\n\n\nView files:\n\n %s $file.rldzip -v\n\nExample:\n %s fileE.rldzip -v\n\n", v, v, v, v); } void runoptions(int c, char **v){ int i; if(c < 2){ printf("Arguments missing! Use -h for help"); } else{ for(i=0; i<c; i++) if(strcmp(v[i], "-h") == 0){ help(v[0]); exit(2); } for(i=0; i<c; i++) if(strcmp(v[i], "-v") == 0){ if(c != 3){ printf("Arguments misused! Use -h for help"); exit(2); } else { printf("-%s-", v[1]); readcont(v[1]); } } } if(strcmp(v[c-1], "-a") == 0) archive(c-2, v); } main(int argc, char **argv) { runoptions(argc, argv); }

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  • Is .gitignore not working or I have misunderstood it?

    - by Shubham
    I am very new to git. I have a .gitignore in the my working folder. *.jpg *.gif *.png system/* */Zend/* .idea/*.* Well, I did git init and then git add *. At this it worked fine and ignored the above files. But when I did some changes, ran the same command it puts the ignored files into staging area. The reason why I am using git add * is because I work on many files and adding each file would be a overkill. Update: Here are messages when I run git add * second time.. #new file: application/vendors/Zend/XmlRpc/Value/String.php #new file: application/vendors/Zend/XmlRpc/Value/Struct.php ... The list is too long.

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  • RAII: Initializing data member in const method

    - by Thomas Matthews
    In RAII, resources are not initialized until they are accessed. However, many access methods are declared constant. I need to call a mutable (non-const) function to initialize a data member. Example: Loading from a data base struct MyClass { int get_value(void) const; private: void load_from_database(void); // Loads the data member from database. int m_value; }; int MyClass :: get_value(void) const { static bool value_initialized(false); if (!value_initialized) { // The compiler complains about this call because // the method is non-const and called from a const // method. load_from_database(); } return m_value; } My primitive solution is to declare the data member as mutable. I would rather not do this, because it suggests that other methods can change the member. How would I cast the load_from_database() statement to get rid of the compiler errors?

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