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  • C: reading file and populating struct

    - by deostroll
    Hi, I have a structure with the following definition: typedef struct myStruct{ int a; char* c; int f; } OBJECT; I am able to populate this object and write it to a file. However I am not able to read the char* c value in it...while trying to read it, it gives me a segmentation fault error. Is there anything wrong with my code: //writensave.c #include "mystruct.h" #include <stdio.h> #include <string.h> #define p(x) printf(x) int main() { p("Creating file to write...\n"); FILE* file = fopen("struct.dat", "w"); if(file == NULL) { printf("Error opening file\n"); return -1; } p("creating structure\n"); OBJECT* myObj = (OBJECT*)malloc(sizeof(OBJECT)); myObj->a = 20; myObj->f = 45; myObj->c = (char*)calloc(30, sizeof(char)); strcpy(myObj->c, "This is a test"); p("Writing object to file...\n"); fwrite(myObj, sizeof(OBJECT), 1, file); p("Close file\n"); fclose(file); p("End of program\n"); return 0; } Here is how I am trying to read it: //readnprint.c #include "mystruct.h" #include <stdio.h> #define p(x) printf(x) int main() { FILE* file = fopen("struct.dat", "r"); char* buffer; buffer = (char*) malloc(sizeof(OBJECT)); if(file == NULL) { p("Error opening file"); return -1; } fread((void *)buffer, sizeof(OBJECT), 1, file); OBJECT* obj = (OBJECT*)buffer; printf("obj->a = %d\nobj->f = %d \nobj->c = %s", obj->a, obj->f, obj->c); fclose(file); return 0; }

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  • passing an array struture as an array

    - by Matias
    I'm having trouble passing a struture array as a parameter of a funtion struct Estructure{ int a; intb; }; and a funtion Begining(Estructure &s1[]) { //modifi the estructure s1 }; and the main would be something like this int main() { Estructure m[200]; Begining(m); }; is this valid?

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  • gets (variable)

    - by borlee
    can anyone tell me why gets(abc) works with char[] but not with int? int abc; char name[] = "lolrofl"; printf("Hello %s.\n",name); printf("\n "); fflush(stdin); gets (abc); printf("\n die zahl ist %i.\n",abc); system("Pause"); return(0);

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  • Implementing a very simple 'Wine Rating System' in Haskell

    - by Alex N
    Hello, I have just started learning Haskell and have got stumped on how to add a rating to a custom data type. The data type I'm using has a name, a year and a tuple (userName and their rating), it looks like: data Wine = Wine String Int [Rating] deriving (Eq,Ord,Show,Read) type Rating = (String, Int) I wanted to allow a user to rate a given wine from a database, stored as [Wine] but cant figure out how to to it. Any pointers or suggestions would be greatly appreciated! Thanks.

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  • is hashCode() must return a prime number

    - by subhashis
    The signature of the hashCode() method is public int hashCode(){ return x; } in this case x must be an int(primitive) but plz can anyone explain it to me that the number which the hashCode() returns must be a prime number, even number...etc or there is no specification ? the reason behind i am asking this question is i have seen it in different ids the auto generated code always returns a prime number, so i need to know why? thanks in advance

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  • How can I share dynamic data array between Applications?

    - by Ehsan
    Hi, I use CreateFileMapping, but this method was not useful,because only static structure can be shared by this method. for example this method is good for following structure: struct MySharedData { unsigned char Flag; int Buff[10]; }; but it's not good for : struct MySharedData { unsigned char Flag; int *Buff; }; would be thankful if somebody guide me on this, Thanks in advance!

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  • JUnit for Functions with Void Return Values

    - by RobotNerd
    I've been working on a Java application where I have to use JUnit for testing. I am learning it as I go. So far I find it to be useful, especially when used in conjunction with the Eclipse JUnit plugin. After playing around a bit, I developed a consistent method for building my unit tests for functions with no return values. I wanted to share it here and ask others to comment. Do you have any suggested improvements or alternative ways to accomplish the same goal? Common Return Values First, there's an enumeration which is used to store values representing test outcomes. public enum UnitTestReturnValues { noException, unexpectedException // etc... } Generalized Test Let's say a unit test is being written for: public class SomeClass { public void targetFunction (int x, int y) { // ... } } The JUnit test class would be created: import junit.framework.TestCase; public class TestSomeClass extends TestCase { // ... } Within this class, I create a function which is used for every call to the target function being tested. It catches all exceptions and returns a message based on the outcome. For example: public class TestSomeClass extends TestCase { private UnitTestReturnValues callTargetFunction (int x, int y) { UnitTestReturnValues outcome = UnitTestReturnValues.noException; SomeClass testObj = new SomeClass (); try { testObj.targetFunction (x, y); } catch (Exception e) { UnitTestReturnValues.unexpectedException; } return outcome; } } JUnit Tests Functions called by JUnit begin with a lowercase "test" in the function name, and they fail at the first failed assertion. To run multiple tests on the targetFunction above, it would be written as: public class TestSomeClass extends TestCase { public void testTargetFunctionNegatives () { assertEquals ( callTargetFunction (-1, -1), UnitTestReturnValues.noException); } public void testTargetFunctionZeros () { assertEquals ( callTargetFunction (0, 0), UnitTestReturnValues.noException); } // and so on... } Please let me know if you have any suggestions or improvements. Keep in mind that I am in the process of learning how to use JUnit, so I'm sure there are existing tools available that might make this process easier. Thanks!

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  • wchar to char in c++

    - by Chris
    I have a Windows CE console application that's entry point looks like this int _tmain(int argc, _TCHAR* argv[]) I want to check the contents of argv[1] for "-s" convert argv[2] into an integer. I am having trouble narrowing the arguments or accessing them to test. I initially tried the following with little success if (argv[1] == L"-s") I also tried using the narrow function of wostringstream on each character but this crashed the application. Can anyone shed some light? Thanks

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  • primary key datatype in sql server database

    - by ooo
    i see after installing the asp.net membership tables, they use the data type "uniqueidentifier" for all of the primary key fields. I have been using "int" data type and doing increment by one on inserts. Is there any particular benefits to using the uniqueIdentifier data type compared to my current model of using int and auto increments on new inserts ?

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  • Scala: can't write setter without getter?

    - by IttayD
    This works: class ButtonCountObserver { private var cnt = 0 // private field def count = cnt // reader method def count_=(newCount: Int) = cnt = newCount // writer method // ... } val b = new ButtonCountObserver b.count = 0 But this doesn't class ButtonCountObserver { private var cnt = 0 // private field def count_=(newCount: Int) = cnt = newCount // writer method // ... } val b = new ButtonCountObserver b.count = 0 I get: error: value count is not a member of ButtonCountObserver Is it possible to create a setter (with the syntactic sugar) without a getter?

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  • What does assert do?

    - by peiska
    What does assert do? for example in the function? private static int charAt(String s, int d) { assert d >= 0 && d <= s.length(); if (d == s.length()) return -1; return s.charAt(d); }

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  • How optimize by lambda expression

    - by simply denis
    I have a very similar function is only one previous report and the other future, how can I optimize and write beautiful? public bool AnyPreviousReportByGroup(int groupID) { if(this.GroupID == groupID) { return true; } else { return PreviousReport.AnyPreviousReportByGroup(groupID); } } public bool AnyNextReportByGroup(int groupID) { if (this.GroupID == groupID) { return true; } else { return NextReport.AnyNextReportByGroup(groupID); } }

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  • Why this query is so slow?

    - by Silver Light
    This query appears in mysql slow query log: it takes 11 seconds. INSERT INTO record_visits ( record_id, visit_day ) VALUES ( '567', NOW() ); The table has 501043 records and it's structure looks like this: CREATE TABLE IF NOT EXISTS `record_visits` ( `id` int(11) NOT NULL AUTO_INCREMENT, `record_id` int(11) DEFAULT NULL, `visit_day` date DEFAULT NULL, `visit_cnt` bigint(20) DEFAULT '1', PRIMARY KEY (`id`), UNIQUE KEY `record_id_visit_day` (`record_id`,`visit_day`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 ; What could be wrong? Why this INSERT takes so long?

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  • Why is the content of slice not changed in GO?

    - by Kid
    I thought that in GO language, slices are passed by reference. But why the following code doesn't change the content of slice c? Am I missing something? Thank you. package main import ( "fmt" ) func call(c []int) { c = append(c, 1) fmt.Println(c) } func main() { c := make([]int, 1, 5) fmt.Println(c) call(c) fmt.Println(c) } The result printed is: [0] [0 1] [0] while I was expecting [0] [0 1] [0 1]

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  • Providing unique layout for specific resolution in Android 2.3.3

    - by user1384991
    I need to use specific xml-layouts based on screen resolution, not size. So, the first design is used for resolution <= 480x800, and the second - for resolution = 480x800. How is it done ? update. Possible solution: Display display = ((WindowManager) getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay(); final int height = display.getHeight(); final int width = display.getWidth();

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  • C99 variable length automatic array performance

    - by aaa
    Is there significant cpu/memory overhead associated with using automatic arrays with g++/Intel on 64-bit x86 linux platform? int function(int N) { double array[N]; overhead compared to allocating array before hand (assuming function is called multiple times) overhead compared to using new overhead compared to using malloc The range of N may be from 1kb to 16kb roughly, stack overrun is not a problem.

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  • KeyNotFound Exception in CSsharp

    - by C Patton
    I'm about ready to bang my head against the wall I have a class called Map which has a dictionary called tiles. class Map { public Dictionary<Location, Tile> tiles = new Dictionary<Location, Tile>(); public Size mapSize; public Map(Size size) { this.mapSize = size; } //etc... I fill this dictionary temporarily to test some things.. public void FillTemp(Dictionary<int, Item> itemInfo) { Random r = new Random(); for(int i =0; i < mapSize.Width; i++) { for(int j=0; j<mapSize.Height; j++) { Location temp = new Location(i, j, 0); int rint = r.Next(0, (itemInfo.Count - 1)); Tile t = new Tile(new Item(rint, rint)); tiles[temp] = t; } } } and in my main program code Map m = new Map(10, 10); m.FillTemp(iInfo); Tile t = m.GetTile(new Location(2, 2, 0)); //The problem line now, if I add a breakpoint in my code, I can clearly see that my instance (m) of the map class is filled with pairs via the function above, but when I try to access a value with the GetTile function: public Tile GetTile(Location location) { if(this.tiles.ContainsKey(location)) { return this.tiles[location]; } else { return null; } } it ALWAYS returns null. Again, if I view inside the Map object and find the Location key where x=2,y=2,z=0 , I clearly see the value being a Tile that FillTemp generated.. Why is it doing this? I've had no problems with a Dictionary such as this so far. I have no idea why it's returning null. and again, when debugging, I can CLEARLY see that the Map instance contains the Location key it says it does not... very frustrating. Any clues? Need any more info? Help would be greatly appreciated :)

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  • An object reference is required for the non-static field, method, or property using global variable

    - by Jose Cardama
    Hello Iam working in a global int in which a variable will be used later. I've made the global variable like this: class Foo { public static int stream = Bass.BASS_StreamCreateFile(path1.Text, 0, 0, BASSFlag.BASS_DEFAULT); } which will be later called like this: Foo.stream and it can also contain more then 1 stream for example stream20,30,etc... The problem here is that it returns me this error: "An object reference is required for the non-static field, method, or property" where I call the text in path1.Text How do I fix this?

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  • Cryptic C++ "thing" (function pointer)

    - by m00st
    What is this syntax for in C++? Can someone point me to the technical term so I can see if I find anything in my text? At first I thought it was a prototype but then the = and (*fn) threw me off... Here is my example: void (*fn) (int&,int&) = x;

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  • Question with "extern" in C

    - by why
    When programming, I would like to split one large file(which contains main function) to many small files, so there is one common case: functions in small files can modify the var from main file, so i think extern is very useful! for instance: in main.c extern int i = 100; in small.c extern int i; fprintf(stdout, "var from main file: %d\n", i); I just want to know is my understanding right?

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  • C# coding standards for private member variables [closed]

    - by Sasha
    I saw two common approaches for coding standards for private member variables: class Foo { private int _i; private string _id; } and class Foo { private int m_i; private string m_id; } I believe the latter is coming from C++. Also, many people specify type before the member variable: double m_dVal -- to indicate that is is a nonconstant member variable of the type double? What are the conventions in C#?

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  • Database design (MySql)::should we put html data in text field inside database table or more efficie

    - by meyosef
    Hi, We building big Web Application and we use mysql, we want to make mysql database more fast. Some of us think if we will put message html body inside table and not inside text.txt in will make database heavy and not fast. Thanks, *Part of main table that hold message: option 1:hold html message body inside database message { id (int) subject (varchar) body (text) } option 2: hold html message body inside body1.txt file message { id (int) subject (varchar) file_body_path (varchar) } *

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