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• How to build up a lookup table in microcontroller?

  - by GiGi

  Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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• usage of 2 charectors in single qoutes in c

  - by user1632141

  #include<stdio.h> int main() { char ch = 'A'; printf("%d\n",'ag'); printf("%d\n",'a'); printf("%d, %d, %d, %d", sizeof(ch), sizeof('a'), sizeof('Ag'), sizeof(3.14f)); return 0; } I used to have many doubts on the output of this question while running on g++ and gcc. But I have cleared almost all the doubts by referring these links: Single and double quotes in C/C++ Single quotes vs. double quotes in C I still need to understand one thing about the output of this question. Can someone please explain the output of printf("%d\n",'ag'); mentioned above in the program. How is it actually stored in the memory? The output for the program on the Linux/GCC platform is: 24935 97 1, 4, 4, 4

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• File in binary form

  - by Abhi

  Dear All I want to write data into the file in binary form. I was trying using the mentioned below FILE *fp = fopen("binaryoutput.rgb888", "ab+"); for(int m=0; m<height; m++) { for (int n=0; n< width; n++) { temp = (pOutputImg+m*3+n*3); // here temp is a pointer to a unsigned char fprintf(fp,"%u",*temp); } } fclose(fp); I am able to get data which is strored at pOutputImg but not in binary form. Can anyone guide me the correct step.. Thanks in advance

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• Unit testing with serialization mock objects in C++

  - by lhumongous

  Greetings, I'm fairly new to TDD and ran across a unit test that I'm not entirely sure how to address. Basically, I'm testing a couple of legacy class methods which read/write a binary stream to a file. The class functions take a serializable object as a parameter, which handles the actual reading/writing to the file. For testing this, I was thinking that I would need a serialization mock object that I would pass to this function. My initial thought was to have the mock object hold onto a (char*) which would dynamically allocate memory and memcpy the data. However, it seems like the mock object might be doing too much work, and might be beyond the scope of this particular test. Is my initial approach correct, or can anyone think of another way of correctly testing this? Thanks!

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• So, I guess I can't use "&&" in the Python if conditional. Any help?

  - by Sergio Tapia

  Here's my code: # F. front_back # Consider dividing a string into two halves. # If the length is even, the front and back halves are the same length. # If the length is odd, we'll say that the extra char goes in the front half. # e.g. 'abcde', the front half is 'abc', the back half 'de'. # Given 2 strings, a and b, return a string of the form # a-front + b-front + a-back + b-back def front_back(a, b): # +++your code here+++ if len(a) % 2 == 0 && len(b) % 2 == 0: return a[:(len(a)/2)] + b[:(len(b)/2)] + a[(len(a)/2):] + b[(len(b)/2):] else: #todo! Not yet done. :P return I'm getting an error in the IF conditional. What am I doing wrong?

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• Operator + for matrices in C++

  - by cibercitizen1

  I suppose the naive implementation of a + operator for matrices (2D for instance) in C++ would be: class Matrix { Matrix operator+ (Matrix other) const { Matrix result; // fill result with *this.data plus other.data return result; } } so we could use it like Matrix a; Matrix b; Matrix c; c = a + b; Right? But if matrices are big this is not efficient as we are doing one not-necessary copy (return result). Therefore, If we wan't to be efficient we have to forget the clean call: c = a + b; Right? What would you suggest / prefer ? Thanks.

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• Why is this c++ string concatenation missing a space?

  - by danutenshu

  I am working with c++ strings, and am a beginner at programming. I am expecting: 99 Red Balloons But I am receiving: 99 RedBalloons Why is that? #include <string> #include <iostream> using namespace std; int main() { string text = "9"; string term( "9 "); string info = "Toys"; string color; char hue[4] = {'R','e','d','\0'}; color = hue; info = "Balloons"; text += (term + color + info); cout << endl << text << endl; return 0; }

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• From my code, I can't trace the out of bounds exception.

  - by Matt

  public override Models.CalculationNode Parse(string expression) { var calNode = new Models.CalculationNode(); int i = expression.Length; char[] x = expression.ToCharArray(); string temp = ""; //Backwards assembly of the tree //Right Node while (!IsOperator(x[i]) && i > 0) { if (!x[i].Equals(' ')) temp = x[i] + temp; i--; } } It has been a while since I've used trees and I'm getting an out of bounds exception in the while loop.

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• IntelliSense: expression must have integral or enum type

  - by user1743737

  Guys i need someone fix this problem ? when i compile that code i have this error: Error: IntelliSense: expression must have integral or enum type i have problem in this part: Console(0, V("seta sv_hostname " + servername + ";\n")); so how i can fix that if (strncmp(command, V("exec config_mp"), 14) == 0) { if (GAME_MODE == 'D') { CIniReader iniReader(V(".\\teknogods.ini")); char *servername = iniReader.ReadString(V("Settings"),V("Servername"),""); if (strcmp(servername,"") == 0) { info("Server name set to defult."); } else { //Console(0, V("seta scr_teambalance 1;\n")); Console(0, V("seta sv_hostname " + servername + ";\n")); info("server name set to: %s.", servername); } } }

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• C++, create an instance from a static method

  - by Manux

  Hello, let's say I want my users to use only one class, say SpecialData. Now, this data class would have many methods, and depending on the type of data, the methods do different things, internally, but return externally similar results. Therefore my wanting to have one "public" class and other "private", child classes that would change the behavior of methods, etc... It would be amazingly more simple for some types of data that need to be built to do something like this: SpecialData& sm = SpecialData::new_supermatrix(); and new_supermatrix() would return a SuperMatrix instance, which inherits from most behaviors of SpecialData. my header: static SpecialData& new_supermatrix(); my cpp: SpecialData& SpecialData::new_supermatrix()(){ return SuperMatrix(MATRIX_DEFAULT_MAGNITUDE,1000,1239,FLOAT32,etc...); } The problem is, I get this error, which is probably logical due to the circumstances: invalid initialization of non-const reference of type ‘SpecialData&’ from a temporary of type ‘SpecialData’ So, any ideas?

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• the problem only happens when i try create a release...

  - by ace

  I'm sorry if im not presenting this right, but i trully cannot understand what the problem is. i have a project to hand in, a code of 600 lines defined within a main, .cpp, and header file. if i compile the project with just a debugger and no release, it's fine. when i create it with the release, the following error occurs, for every function!!! 1st error: |36|multiple definition of `countLines(int&, std::vector const&)'| 2nd error: |36|first defined here| if someone will allow me and i can send them the entire code, that would be awesome - i have to have this done within 3 hours.

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• 1 bug to kill... Letting PHP Generate The Canonical.

  - by Sam

  Hi folks, for building a clean canonical url, that always returns 1 base URL, im stuck in following case: <?php # every page $extensions = $_SERVER['REQUEST_URI']; # path like: /en/home.ast?ln=ja $qsIndex = strpos($extensions, '?'); # removes the ?ln=de part $pageclean = $qsIndex !== FALSE ? substr($extensions, 0, $qsIndex) : $extensions; $canonical = "http://website.com" . $pageclean; # basic canonical url ?> <html><head><link rel="canonical" href="<?=$canonical?>"></head> when URL : http://website.com/de/home.ext?ln=de canonical: http://website.com/de/home.ext BUT I want to remove the file extension aswell, whether its .php, .ext .inc or whatever two or three char extension .[xx] or .[xxx] so the base url becomes: http://website.com/en/home Aaah much nicer! but How do i achieve that in current code? Any hints are much appreciated +! (other advices for proper canonical usage in this multi-lingual environment are welcome as well)

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• C++ STL map.find() not finding my stuff

  - by Joe

  Hello, I have constructed a map and loaded it with data. If I iterate over all the elements I see they are all valid. However, the find method doesn't find my item. I'm sure it's something stupid I am doing. Here is snippet: // definitions // I am inserting a person class and using the firstname as the key typedef std::map<char*,Person *> mapType; mapType _myMap; mapType::iterator _mapIter; ... Person *pers = new Person(FirstName, LastName, Address, Phone); _myMap.insert(make_pair(pers->firstName, pers); ... ...later.... _mapIter = _myMap.find(firstName); // returns map.end _mapIter = _myMap.find("joe"); // returns map.end and I have no idea why :(

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• Casting a container of shared_ptr

  - by Jamie Cook

  Hi all, I have a method void foo(list<shared_ptr<Base>>& myList); Which I'm trying to call with a two different types of lists, one of DerivedClass1 and one of DerivedClass2 list<shared_ptr<DerivedClass1>> myList1; foo(myList1); list<shared_ptr<DerivedClass2>> myList2; foo(myList2); However this obviously generates a compiler error error: a reference of type "std::list<boost::shared_ptr<Base>, std::allocator<boost::shared_ptr<Base>>> &" (not const-qualified) cannot be initialized with a value of type "std::list<boost::shared_ptr<DerivedClass1>, std::allocator<boost::shared_ptr<DerivedClass1>>>" Is there any easy way to cast a container of shared_ptr? Of alternate containers that can accomplish this?

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• c++/cli pass (managed) delegate to unmanaged code

  - by Ron Klein

  How do I pass a function pointer from managed C++ (C++/CLI) to an unmanaged method? I read a few articles, like this one from MSDN, but it describes two different assemblies, while I want only one. Here is my code: 1) Header (MyInterop.ManagedCppLib.h): #pragma once using namespace System; namespace MyInterop { namespace ManagedCppLib { public ref class MyManagedClass { public: void DoSomething(); }; }} 2) CPP Code (MyInterop.ManagedCppLib.cpp) #include "stdafx.h" #include "MyInterop.ManagedCppLib.h" #pragma unmanaged void UnmanagedMethod(int a, int b, void (*sum)(const int)) { int result = a + b; sum(result); } #pragma managed void MyInterop::ManagedCppLib::MyManagedClass::DoSomething() { System::Console::WriteLine("hello from managed C++"); UnmanagedMethod(3, 7, /* ANY IDEA??? */); } I tried creating my managed delegate and then I tried to use Marshal::GetFunctionPointerForDelegate method, but I couldn't compile.

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• Why would I get a bus error or segmentation fault when calling free() normally?

  - by chucknelson

  I have a very simple test program, running on Solaris 5.8: #include <stdio.h> #include <stdlib.h> int main(void) { char *paths; paths = getenv("PATH"); printf("Paths: %s\n", paths); free(paths); // this causes a bus error return 0; } If I don't call free() at the end, it displays the message fine and exits. If I include the free() call, it crashes with a bus error. I've had other calls to free(), in other programs, cause segmentation faults as well. Even if I allocate the memory for *paths myself, free() will cause a bus error. Is there some reason trying to free up the memory is causing a crash?

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• Column.DbType affecting runtime behavior

  - by leppie

  Hi According to the MSDN docs, the DbType property/attribute of a Column type/element is only used for database creation. Yet, today, when trying to submit data to an IMAGE column on a SQLCE database (not sure if only on CE), I got an exception of 'Data truncated to 8000 bytes'. This was due to the DbType still being defined as VARBINARY(MAX) which SQLCE does not support. Changing the type to IMAGE in the DbType fixes the issue. So what other surprises does Linq2SQL attributes hold in store? Is this a bug or intended? Should I report it to MS? UPDATE After getting the answer from Guffa, I tested it, but it seems for NVARCHAR(10) adding a 11 char length string causes a SQL exception, and not Linq2SQL one. The data was truncated while converting from one data type to another. [ Name of function(if known) = ] A first chance exception of type 'System.Data.SqlServerCe.SqlCeException' occurred in System.Data.SqlServerCe.dll

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• set file's icon in a command line utility not working

  - by Ief2

  I just began to work with Objective-C and I'm managing pretty well. My last challenge was to make a command line utility, which I could than use in AppleScript. But my code does not work, not in the terminal, not in the AppleScript. So I'm asking you, what's the error in this peace of code, that should be very plain and easy? int main(int argc, char *argv[]) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; // -imagePath // -filePath NSUserDefaults *args = [NSUserDefaults standardUserDefaults]; NSString *soundPath = [args stringForKey:@"imagePath"]; NSString *filePath = [args stringForKey:@"filePath"]; BOOL worked = [[NSWorkspace sharedWorkspace] setIcon:[[NSImage alloc] initWithContentsOfFile:soundPath] forFile:filePath options:0]; NSLog(@"Worked: %i",worked); [pool release]; return 0; }

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• String useless character strip - PHP

  - by Zoltan Repas

  Hi! I've got a huge problem. I made a special ID for the things in our webpage. Let's see an example: H0059 - this is the special ID called registration number. The last two chars are the things' id. I'd like to cut off the useless characters, to get the real ID, what means strip the first char, and all the 0s before any other numbers. (Example: L0745 = 745, V1754 = 1754, L0003 = 3, B0141 = 141, P0040 = 40, V8000 = 8000) Please help me in this. I've tried with strreplace and explode but failed :( Thanks for the help.

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• Boost singleton and undefined reference

  - by Ockonal

  Hello, I globally use singleton pattern in my project. To make it easier - boost::singleton. Current project uses Ogre3d library for rendering. Here is some class: class GraphicSystem : public singleton<GraphicSystem> { private: Ogre::RenderWindow *mWindow; public: Ogre::RenderWindow *getWindow() const { return mWindow; } }; In GraphicSystem constructor I fill the mWindow value: mWindow = mRoot->createRenderWindow(...); I cheked it, everything makes normally. So, now I have to use handler for the window in input system (to get window handle). Somewhere else in another class: Ogre::RenderWindow *temp = GraphicSystem::get_mutable_instance().getWindow(); GraphicSystem::get_mutable_instance().getWindow()->getCustomAttribute("WINDOW", &mWindowHandle); temp is 0x00, and there is segfault at last line (getting custon attribute). I can't understand, why does singleton returns undefined pointer for the window. All another singleton-based classes work well.

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• How to find validity of a string of parentheses, curly brackets and square brackets?

  - by Rajendra

  I recently came in contact with this interesting problem. You are given a string containing just the characters '(', ')', '{', '}', '[' and ']', for example, "[{()}]", you need to write a function which will check validity of such an input string, function may be like this: bool isValid(char* s); these brackets have to close in the correct order, for example "()" and "()[]{}" are all valid but "(]", "([)]" and "{{{{" are not! I came out with following O(n) time and O(n) space complexity solution, which works fine: Maintain a stack of characters. Whenever you find opening braces '(', '{' OR '[' push it on the stack. Whenever you find closing braces ')', '}' OR ']' , check if top of stack is corresponding opening bracket, if yes, then pop the stack, else break the loop and return false. Repeat steps 2 - 3 until end of the string. This works, but can we optimize it for space, may be constant extra space, I understand that time complexity cannot be less than O(n) as we have to look at every character. So my question is can we solve this problem in O(1) space?

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• compare function for dates

  - by Chris

  I have struct as: struct stored { char *dates; // 12/May/2010, 10/Jun/2010 etc.. int ctr; }; // const struct stored structs[] = {{"12/May/2010", 1}, {"12/May/2011", 1}, {"21/May/2009", 4}, {"12/May/2011", 3}, {"10/May/2011", 8}, {"12/May/2011", 4 }}; What I want to do is to sort struct 'stored' by stored.dates. qsort(structs, 9, sizeof(struct stored*), sortdates); // sortdates function I'm not quite sure what would be a good way to sort those days? Compare them as c-strings?

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• Is the time cost constant when bulk inserting data into an indexed table?

  - by SiLent SoNG

  I have created an archive table which will store data for selecting only. Daily there will be a program to transfer a batch of records into the archive table. There are several columns which are indexed; while others are not. I am concerned with time cost per batch insertion: - 1st batch insertion: N1 - 2nd batch insertion: N2 - 3rd batch insertion: N3 The question is: will N1, N2, and N3 roughly be the same, or N3 N2 N1? That is, will the time cost be a constant or incremental, with existence of several indexes? All indexes are non-clustered. The archive table structure is this: create table document ( doc_id int unsigned primary key, owner_id int, -- indexed title smalltext, country char(2), year year(4), time datetime, key ix_owner(owner_id) }

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• C++: Template functor cannot deduce reference type

  - by maciekp

  I've got a functor f, which takes a function func and a parameter t of the same type as func. I cannot pass g to f because of compilation error (no matching function for call to f(int&, void (&)(int&)) ). If g would take non-reference parameter g(int s), compilation finishes. Or if I manually specify template parameter f(i, g), compilation also finishes. template<typename T> void f(T t, void (*func)(T)) {} void g(int& s) {} int main(int, char*[]) { int i = 7; f(i, g); // compilation error here return 0; } How can I get deduction to work?

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• problem in reading output of dd command using pipe

  - by Ummar

  I am developing an application, in which I want to redirect the output (progress information) of dd command to my C++ program, but it is not actually getting the output, here is the code FILE * progressInfo = popen("gzip -dc backup/backup.img.gz | pv -ptrbe -i 2 -s 2339876653 | dd of=/dev/sdb","r"); if(!progressInfo) { return -1; } char buf[1024]; while(fgets(buff, sizeof(buff),progressInfo)!=NULL) { std::cout << buff << endl; } but the problem is the progress information is not received in buff, and the output is continuously printed on terminal, and above program halts on while(fgets(buff, sizeof(buff),progressInfo)!=NULL), and as soon as the dd operation is completed, the very next line to loop block is executed. if anyone has any idea why the output is not returned to buff, and its continuously retuned on terminal?

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