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  • Hibernate exception

    - by Mark
    Hi all, im new to hibernate! i have followed the netbeans tutorial on creating a hibernate enabled application. after sucessfully creating a database in mysql workbench i reversed engineered the pojos etc and then tried to run a simple query(from Course) and got the following org.hibernate.MappingException: An association from the table coursemodule refers to an unmapped class: DAL.Module at org.hibernate.cfg.Configuration.secondPassCompileForeignKeys(Configuration.java:1252) at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1170) at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:324) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1286) at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:859) heres the generated class for Course package DAL; // Generated 02-May-2010 16:41:16 by Hibernate Tools 3.2.1.GA import java.util.HashSet; import java.util.Set; /** * Course generated by hbm2java */ public class Course implements java.io.Serializable { private int id; private String name; private Set<Module> modules = new HashSet<Module>(0); public Course() { } public Course(int id, String name) { this.id = id; this.name = name; } public Course(int id, String name, Set<Module> modules) { this.id = id; this.name = name; this.modules = modules; } public int getId() { return this.id; } public void setId(int id) { this.id = id; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public Set<Module> getModules() { return this.modules; } public void setModules(Set<Module> modules) { this.modules = modules; } } and its config file course.hbm.xml <?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Generated 02-May-2010 16:41:16 by Hibernate Tools 3.2.1.GA --> <hibernate-mapping> <class name="DAL.Course" table="course" catalog="walkthrough"> <id name="id" type="int"> <column name="id" /> <generator class="assigned" /> </id> <property name="name" type="string"> <column name="name" not-null="true" /> </property> <set name="modules" inverse="false" table="coursemodule"> <key> <column name="courseId" not-null="true" unique="true" /> </key> <many-to-many entity-name="DAL.Module"> <column name="moduleId" not-null="true" unique="true" /> </many-to-many> </set> </class> </hibernate-mapping> hibernate.reveng.xml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-reverse-engineering PUBLIC "-//Hibernate/Hibernate Reverse Engineering DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-reverse-engineering-3.0.dtd"> <hibernate-reverse-engineering> <schema-selection match-catalog="Walkthrough"/> <table-filter match-name="walkthrough"/> <table-filter match-name="course"/> <table-filter match-name="module"/> <table-filter match-name="studentmodule"/> <table-filter match-name="attendee"/> <table-filter match-name="student"/> <table-filter match-name="coursemodule"/> <table-filter match-name="session"/> <table-filter match-name="test"/> </hibernate-reverse-engineering> hibernate.cfg.xml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/Walkthrough</property> <property name="hibernate.connection.username">root</property> <property name="hibernate.connection.password">password</property> <property name="hibernate.show_sql">true</property> <property name="hibernate.current_session_context_class">thread</property> <mapping resource="DAL/Student.hbm.xml"/> <mapping resource="DAL/Walkthrough.hbm.xml"/> <mapping resource="DAL/Test.hbm.xml"/> <mapping resource="DAL/Module.hbm.xml"/> <mapping resource="DAL/Session.hbm.xml"/> <mapping resource="DAL/Course.hbm.xml"/> </session-factory> </hibernate-configuration> any ideas on why im getting this exception? ps. test is just a table with an id in it and is not related to anything. running "from Test" works

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  • Mysql : Request to select the last 10 send/received messages to/by different users

    - by Yako malin
    Hello, I want to select the 10 last messages you received OR you sent TO different users. For example the results must be shown like that : 1. John1 - last message received 04/17/10 3:12 2. Thomy - last message sent 04/16/10 1:26 3. Pamela - last message received 04/12/10 3:51 4. Freddy - last message received 03/28/10 9:00 5. Jack - last message sent 03/20/10 4:53 6. Tom - last message received 02/01/10 7:41 ..... Table looks like : CREATE TABLE `messages` ( `id` int(11) NOT NULL AUTO_INCREMENT, `time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `sender` int(11) DEFAULT NULL, `receiver` int(11) DEFAULT NULL, `content` text ) Have someone any solution ? Thanks in advance for your help.

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  • Having template function defination in cpp file - Not work for VC6

    - by Yan Cheng CHEOK
    I have the following source code : // main.cpp #include "a.h" int main() { A::push(100); } // a.cpp #include "a.h" template <class T> void A::push(T t) { } template void A::push(int t); // a.h #ifndef A_H class A { public: template <class T> static void push(T t); }; #endif The code compiled charming and no problem under VC2008. But when come to my beloved VC6, it give me error : main.obj : error LNK2001: unresolved external symbol "public: static void __cdecl A::push(int)" (?push@A@@SAXH@Z) Any workaround? I just want to ensure my function definition is re-inside cpp file.

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  • Scope of variables inside anonymous functions in C#

    - by Vinod
    I have a doubt in scope of varibles inside anonymous functions in C#. Consider the program below: delegate void OtherDel(int x); public static void Main() { OtherDel del2; { int y = 4; del2 = delegate { Console.WriteLine("{0}", y);//Is y out of scope }; } del2(); } My VS2008 IDE gives the following errors: [Practice is a class inside namespace Practice] 1.error CS1643: Not all code paths return a value in anonymous method of type 'Practice.Practice.OtherDel' 2.error CS1593: Delegate 'OtherDel' does not take '0' arguments. It is told in a book: Illustrated C# 2008(Page 373) that the int variable y is inside the scope of del2 definition. Then why these errors.

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  • Why we used double and triple pointer in objective-C or C language?

    - by Rajendra Bhole
    Hi, I confused when i want to take single pointer and when should i take double pointer? In following structure what exactly did? struct objc_class { Class isa; Class super_class; const char *name; long version; long info; long instance_size; struct objc_ivar_list *ivars; struct objc_method_list **methodLists; struct objc_cache *cache; struct objc_protocol_list *protocols; }; Why we use the "**methodLists" double pointer. Edited int sqlite3_get_table( sqlite3 *db, const char zSql, char **pazResult, int *pnRow, int *pnColumn, char *pzErrmsg ); In above scenario what will be meaning of triple pointer char **pazResult?

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  • Compiling netcat on AIX

    - by A.Rashad
    I have been trying to compile netcat.c on AIX for some time (using the command make aix), but the compiler gives me some weird feedback such as : "netcat.c", line 117.12: 1506-275 (S) Unexpected text 'int' encountered. when checked the file netcat.c at line 117, I would find the line (second line in code below): #ifdef HAVE_BIND extern int h_errno; /* stolen almost wholesale from bsd herror.c */ even if I changed the int into char for the same of testing, save the file and re-run the command I get the same error am I missing something in reading the error code?

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  • MYSQL Fast Insert dependent on flag from a seperate table

    - by Stuart P
    Hi all. For work I'm dealing with a large database (160 million + rows a year, 10 years of data) and have a quandary; A large percentage of the data we upload is null data and I'd like to stop it from being uploaded. The data in question is spatial in nature, so I have one table like so: idLocations (Auto-increment int, PK) X (float) Y (foat) Alwaysignore (Bool) Which is used as a reference in a second table like so: idLocations (Int, PK, "FK") idDates (Int, PK, "FK") DATA1 (float) DATA2 (float) ... DATA7 (float) So, Ideally I'd like to find a method where I can do something like: INSERT INTO tblData(idLocations, idDates, DATA1, ..., DATA7) VALUES (...), ..., (...) WHERE VALUES(idLocations) NOT LIKE (SELECT FROM tblLocation WHERE alwaysignore=TRUE ON DUPLICATE KEY UPDATE DATA1=VALUES(DATA1) So, for my large batch of input data (250 values in a block), ignore the inserts where the idLocations matches an idLocations values flagged with alwaysignore. Anyone have any suggestions? Cheers. -Stuart Other details: Running MySQL on a semi-dedicated machine, MyISAM engine for the tables.

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  • Hung JVM consuming 100% CPU

    - by Bogdan
    We have a JAVA server running on Sun JRE 6u20 on Linux 32-bit (CentOS). We use the Server Hotspot with CMS collector with the following options (I've only provided the relevant ones): -Xmx896m -Xss128k -XX:NewSize=384M -XX:MaxPermSize=96m -XX:+UseParNewGC -XX:+UseConcMarkSweepGC Sometimes, after running for a while, the JVM seems to slip into a hung state, whereby even though we don't make any requests to the application, the CPU continues to spin at 100% (we have 8 logical CPUs, so it looks like only one CPU does the spinning). In this state the JVM doesn't respond to SIGHUP signals (kill -3) and we can't connect to it normally with jstack. We CAN connect with "jstack -F", but the output is dodgy (we can see lots of NullPointerExceptions from JStack apparently because it wasn't able to 'walk' some stacks). So the "jstack -F" output seems to be useless. We have run a stack dump from "gdb" though, and we were able to match the thread id that spins the CPU (we found that using "top" with a per-thread view - "H" option) with a thread stack that appears in the gdb result and this is how it looks like: Thread 443 (Thread 0x7e5b90 (LWP 26310)): #0 0x0115ebd3 in CompactibleFreeListSpace::block_size(HeapWord const*) const () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #1 0x01160ff9 in CompactibleFreeListSpace::prepare_for_compaction(CompactPoint*) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #2 0x0123456c in Generation::prepare_for_compaction(CompactPoint*) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #3 0x01229b2c in GenCollectedHeap::prepare_for_compaction() () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #4 0x0122a7fc in GenMarkSweep::invoke_at_safepoint(int, ReferenceProcessor*, bool) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #5 0x01186024 in CMSCollector::do_compaction_work(bool) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #6 0x011859ee in CMSCollector::acquire_control_and_collect(bool, bool) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #7 0x01185705 in ConcurrentMarkSweepGeneration::collect(bool, bool, unsigned int, bool) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #8 0x01227f53 in GenCollectedHeap::do_collection(bool, bool, unsigned int, bool, int) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #9 0x0115c7b5 in GenCollectorPolicy::satisfy_failed_allocation(unsigned int, bool) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #10 0x0122859c in GenCollectedHeap::satisfy_failed_allocation(unsigned int, bool) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #11 0x0158a8ce in VM_GenCollectForAllocation::doit() () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #12 0x015987e6 in VM_Operation::evaluate() () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #13 0x01597c93 in VMThread::evaluate_operation(VM_Operation*) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #14 0x01597f0f in VMThread::loop() () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #15 0x015979f0 in VMThread::run() () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #16 0x0145c24e in java_start(Thread*) () from /usr/java/jdk1.6.0_20/jre/lib/i386/server/libjvm.so #17 0x00ccd46b in start_thread () from /lib/libpthread.so.0 #18 0x00bc2dbe in clone () from /lib/libc.so.6 It seems that a JVM thread is spinning while doing some CMS related work. We have checked the memory usage on the box, there seems to be enough memory available and the system is not swapping. Has anyone come across such a situation? Does it look like a JVM bug? UPDATE I've obtained some more information about this problem (it happened again on a server that has been running for more than 7 days). When the JVM entered the "hung" state it stayed like that for 2 hours until the server was manually restarted. We have obtained a core dump of the process and the gc log. We tried to get a heap dump as well, but "jmap" failed. We tried to use jmap -F but then only a 4Mb file was written before the program aborted with an exception (something about the a memory location not being accessible). So far I think the most interesting information comes from the gc log. It seems that the GC logging stopped as well (possibly at the time when the VM thread went into the long loop): 657501.199: [Full GC (System) 657501.199: [CMS: 400352K->313412K(524288K), 2.4024120 secs] 660634K->313412K(878208K), [CMS Perm : 29455K->29320K(68568K)], 2.4026470 secs] [Times: user=2.39 sys=0.01, real=2.40 secs] 657513.941: [GC 657513.941: [ParNew: 314624K->13999K(353920K), 0.0228180 secs] 628036K->327412K(878208K), 0.0230510 secs] [Times: user=0.08 sys=0.00, real=0.02 secs] 657523.772: [GC 657523.772: [ParNew: 328623K->17110K(353920K), 0.0244910 secs] 642036K->330523K(878208K), 0.0247140 secs] [Times: user=0.08 sys=0.00, real=0.02 secs] 657535.473: [GC 657535.473: [ParNew: 331734K->20282K(353920K), 0.0259480 secs] 645147K->333695K(878208K), 0.0261670 secs] [Times: user=0.11 sys=0.00, real=0.02 secs] .... .... 688346.765: [GC [1 CMS-initial-mark: 485248K(524288K)] 515694K(878208K), 0.0343730 secs] [Times: user=0.03 sys=0.00, real=0.04 secs] 688346.800: [CMS-concurrent-mark-start] 688347.964: [CMS-concurrent-mark: 1.083/1.164 secs] [Times: user=2.52 sys=0.09, real=1.16 secs] 688347.964: [CMS-concurrent-preclean-start] 688347.969: [CMS-concurrent-preclean: 0.004/0.005 secs] [Times: user=0.00 sys=0.01, real=0.01 secs] 688347.969: [CMS-concurrent-abortable-preclean-start] CMS: abort preclean due to time 688352.986: [CMS-concurrent-abortable-preclean: 2.351/5.017 secs] [Times: user=3.83 sys=0.38, real=5.01 secs] 688352.987: [GC[YG occupancy: 297806 K (353920 K)]688352.987: [Rescan (parallel) , 0.1815250 secs]688353.169: [weak refs processing, 0.0312660 secs] [1 CMS-remark: 485248K(524288K)] 783055K(878208K), 0.2131580 secs] [Times: user=1.13 sys =0.00, real=0.22 secs] 688353.201: [CMS-concurrent-sweep-start] 688353.903: [CMS-concurrent-sweep: 0.660/0.702 secs] [Times: user=0.91 sys=0.07, real=0.70 secs] 688353.903: [CMS-concurrent-reset-start] 688353.912: [CMS-concurrent-reset: 0.008/0.008 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 688354.243: [GC 688354.243: [ParNew: 344928K->30151K(353920K), 0.0305020 secs] 681955K->368044K(878208K), 0.0308880 secs] [Times: user=0.15 sys=0.00, real=0.03 secs] .... .... 688943.029: [GC 688943.029: [ParNew: 336531K->17143K(353920K), 0.0237360 secs] 813250K->494327K(878208K), 0.0241260 secs] [Times: user=0.10 sys=0.00, real=0.03 secs] 688950.620: [GC 688950.620: [ParNew: 331767K->22442K(353920K), 0.0344110 secs] 808951K->499996K(878208K), 0.0347690 secs] [Times: user=0.11 sys=0.00, real=0.04 secs] 688956.596: [GC 688956.596: [ParNew: 337064K->37809K(353920K), 0.0488170 secs] 814618K->515896K(878208K), 0.0491550 secs] [Times: user=0.18 sys=0.04, real=0.05 secs] 688961.470: [GC 688961.471: [ParNew (promotion failed): 352433K->332183K(353920K), 0.1862520 secs]688961.657: [CMS I suspect this problem has something to do with the last line in the log (I've added some "...." in order to skip some lines that were not interesting). The fact that the server stayed in the hung state for 2 hours (probably trying to GC and compact the old generation) seems quite strange to me. Also, the gc log stops suddenly with that message and nothing else gets printed any more, probably because the VM Thread gets into some sort of infinite loop (or something that takes 2+ hours).

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  • Setting a value through reflection is not working.

    - by Scott Chamberlain
    I am trying to set a value through reflection. I created this little test program struct headerIndexes { public int AccountNum{ get; set; } public int other { get; set; } public int items { get; set; } } static void Main(string[] args) { headerIndexes headers = new headerIndexes(); headers.AccountNum = 1; Console.WriteLine("Old val: {0}", headers.AccountNum); foreach (var s in headers.GetType().GetProperties()) { if (s.Name == "AccountNum") s.SetValue(headers, 99, null); } Console.WriteLine("New val: {0}", headers.AccountNum); Console.ReadKey(); } Steping thorugh the program i see it correctly does the command s.SetValue(headers, 99, null); however the value of headers.AccountNum stays at 1 when setValue is run. Am I missing a obvious step?

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  • MinGW Doesn't Generate an Object File When Compiling

    - by Nathan Campos
    I've just bought a new laptop for me on the travel, then on my free time, I've started to test MinGW on it by trying to compile my own OS that is written in C++, then I've created all the files needed and the kernel.cpp: extern "C" void _main(struct multiboot_data* mbd, unsigned int magic); void _main( struct multiboot_data* mbd, unsigned int magic ) { char * boot_loader_name =(char*) ((long*)mbd)[16]; /* Print a letter to screen to see everything is working: */ unsigned char *videoram = (unsigned char *) 0xb8000; videoram[0] = 65; /* character 'A' */ videoram[1] = 0x07; /* forground, background color. */ } And tried to compile it with g++ G: g++ -o C:\kernel.o -c kernel.cpp -Wall -Wextra -Werror -nostdlib -nostartfiles -nodefaultlibs kernel.cpp: In function `void _main(multiboot_data*, unsigned int)': kernel.cpp:8: warning: unused variable 'boot_loader_name' kernel.cpp: At global scope: kernel.cpp:4: warning: unused parameter 'magic' G: But it don't create any binary file at C:/. What can I do?

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  • Ordered many-to-many relationship in NHibernate

    - by Kristoffer
    Let's say I have two classes: Item and ItemCollection, where ItemCollection contains an ordered list of Item objects with an index, i.e. the list is ordered in a way specified by the user. Let's also say that they have a many-to-many relationship, an ItemCollection can contain many items and an Item can belong to several ItemCollections. That would, in my head, require three tables in the database. One for Item, one for ItemCollection and one for the ordered mapping. The mapping table would contain three columns: int ItemID int ItemCollectionID int ListIndex QUESTION: How would you design the ItemCollection class? Should the list of Item objects be a list, dictionary or other? What would the NHibernate mapping look like to get the ListIndex into the picture?

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  • Verification GetHashCode and Equals

    - by nettguy
    Does the following code show the correct implementation of overriding GetHashCode ? public class Person { public string fName{get;set;} public string lName { get; set; } public int age { get; set; } public override bool Equals(object obj) { Person p = obj as Person; if (p == null) return false; return ( p.GetType()==this.GetType() && p.fName==this.fName &&p.lName==this.lName && p.age==this.age ); } //I took the below code from Marc Gravell's post,I am not sure whether i have implemented it properly public override int GetHashCode() { unchecked { int hash = 13; hash = (hash * 7) + fName.GetHashCode(); hash = (hash * 7) + lName.GetHashCode(); hash = (hash * 7) + age.GetHashCode(); return hash; } } }

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  • Where is the virtual function call overhead?

    - by Semen Semenych
    Hello everybody, I'm trying to benchmark the difference between a function pointer call and a virtual function call. To do this, I have written two pieces of code, that do the same mathematical computation over an array. One variant uses an array of pointers to functions and calls those in a loop. The other variant uses an array of pointers to a base class and calls its virtual function, which is overloaded in the derived classes to do absolutely the same thing as the functions in the first variant. Then I print the time elapsed and use a simple shell script to run the benchmark many times and compute the average run time. Here is the code: #include <iostream> #include <cstdlib> #include <ctime> #include <cmath> using namespace std; long long timespecDiff(struct timespec *timeA_p, struct timespec *timeB_p) { return ((timeA_p->tv_sec * 1000000000) + timeA_p->tv_nsec) - ((timeB_p->tv_sec * 1000000000) + timeB_p->tv_nsec); } void function_not( double *d ) { *d = sin(*d); } void function_and( double *d ) { *d = cos(*d); } void function_or( double *d ) { *d = tan(*d); } void function_xor( double *d ) { *d = sqrt(*d); } void ( * const function_table[4] )( double* ) = { &function_not, &function_and, &function_or, &function_xor }; int main(void) { srand(time(0)); void ( * index_array[100000] )( double * ); double array[100000]; for ( long int i = 0; i < 100000; ++i ) { index_array[i] = function_table[ rand() % 4 ]; array[i] = ( double )( rand() / 1000 ); } struct timespec start, end; clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start); for ( long int i = 0; i < 100000; ++i ) { index_array[i]( &array[i] ); } clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end); unsigned long long time_elapsed = timespecDiff(&end, &start); cout << time_elapsed / 1000000000.0 << endl; } and here is the virtual function variant: #include <iostream> #include <cstdlib> #include <ctime> #include <cmath> using namespace std; long long timespecDiff(struct timespec *timeA_p, struct timespec *timeB_p) { return ((timeA_p->tv_sec * 1000000000) + timeA_p->tv_nsec) - ((timeB_p->tv_sec * 1000000000) + timeB_p->tv_nsec); } class A { public: virtual void calculate( double *i ) = 0; }; class A1 : public A { public: void calculate( double *i ) { *i = sin(*i); } }; class A2 : public A { public: void calculate( double *i ) { *i = cos(*i); } }; class A3 : public A { public: void calculate( double *i ) { *i = tan(*i); } }; class A4 : public A { public: void calculate( double *i ) { *i = sqrt(*i); } }; int main(void) { srand(time(0)); A *base[100000]; double array[100000]; for ( long int i = 0; i < 100000; ++i ) { array[i] = ( double )( rand() / 1000 ); switch ( rand() % 4 ) { case 0: base[i] = new A1(); break; case 1: base[i] = new A2(); break; case 2: base[i] = new A3(); break; case 3: base[i] = new A4(); break; } } struct timespec start, end; clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start); for ( int i = 0; i < 100000; ++i ) { base[i]->calculate( &array[i] ); } clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end); unsigned long long time_elapsed = timespecDiff(&end, &start); cout << time_elapsed / 1000000000.0 << endl; } My system is LInux, Fedora 13, gcc 4.4.2. The code is compiled it with g++ -O3. The first one is test1, the second is test2. Now I see this in console: [Ignat@localhost circuit_testing]$ ./test2 && ./test2 0.0153142 0.0153166 Well, more or less, I think. And then, this: [Ignat@localhost circuit_testing]$ ./test2 && ./test2 0.01531 0.0152476 Where are the 25% which should be visible? How can the first executable be even slower than the second one? I'm asking this because I'm doing a project which involves calling a lot of small functions in a row like this in order to compute the values of an array, and the code I've inherited does a very complex manipulation to avoid the virtual function call overhead. Now where is this famous call overhead?

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  • Using fscanf with dynamically allocated buffer.

    - by ryyst
    Hi, I got the following code: char buffer[2047]; int charsRead; do { if(fscanf(file, "%2047[^\n]%n%*c", buffer, &charsRead) == 1) { // Do something } } while (charsRead == 2047); I wanted to convert this code to use dynamically allocated variables so that when calling this code often I won't get heavy memory leakage. Thus, I tried this: char *buffer = malloc(sizeof(char) * 2047); int *charsRead = malloc(sizeof(int)); do { if(fscanf(file, "%2047[^\n]%n%*c", *buffer, charsRead) == 1) { // Do something } } while (*charsRead == 2047); Unfortunately, this does not work. I always get “EXC_BAD_ACCESS” errors, just before the if-statement with the fscanf call. What am I doing wrong? Thanks for any help! -- Ry

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  • Division, Remainders and only Real Numbers Allowed

    - by Senica Gonzalez
    Trying to figure out this pseudo code. The following is assumed.... I can only use unsigned and signed integers (or long). Division returns a real number with no remainder. MOD returns a real number. Fractions and decimals are not handled. INT I = 41828; INT C = 15; INT D = 0; D = (I / 65535) * C; How would you handle a fraction (or decimal value) in this situation? Is there a way to use negative value to represent the remainder? In this example I/65535 should be 0.638, however, with the limitations, I get 0 with a MOD of 638. How can I then multiply by C to get the correct answer? Hope that makes sense.

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  • typedef of a template with a template type as its parameter

    - by bryan sammon
    Im having a problem with a typedef below, I can seem to get it right: template <typename T> struct myclass1 { static const int member1 = T::GetSomeInt(); }; template <int I> struct myclass2 { typedef myclass1< myclass2<I> > anotherclass; static int GetSomeInt(); }; anotherclass MyObj1; // ERROR here not instantiating the class When I try and initialize a anotherclass object, it gives me an error. Any idea what I am doing wrong? There seems to be a problem with my typedef. Any help is appreciated, Thanks Bryan

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  • Scalaz Kleisli question

    - by oxbow_lakes
    There is a trait called Kleisli in the scalaz library. Looking at the code: import scalaz._ import Scalaz._ type StringPair = (String, String) val f: Int => List[String] = (i: Int) => List((i |+| 1).toString, (i |+| 2).toString) val g: String => List[StringPair] = (s: String) => List("X" -> s, s -> "Y") val k = kleisli(f) >=> kleisli(g) //this gives me a function: Int => List[(String, String)] Calling the function k with the value of 2 gives: println( k(2) ) //Prints: List((X,3), (3,Y), (X,4), (4,Y)) My question is: how would I use Scalaz to combine f and g to get a function m such that the output of m(2) would be: val m = //??? some combination of f and g println( m(2) ) //Prints: List((X,3), (X,4), (3,Y), (4,Y)) Is this even possible?

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  • is it wasteful/bad design to use a vector/list where in most instances it will only have one element

    - by lucid
    is it wasteful/bad design to use a vector/list where in most instances it will only have one element? example: class dragon { ArrayList<head> = new ArrayList<head> Heads; tail Tail = new tail(); body Body = new body(); dragon() { theHead=new head(); Heads.add(theHead); } void nod() { for (int i=0;i<Heads.size();i++) { heads.get(i).GoUpAndDown(); } } } class firedragon extends dragon { } class icedragon extends dragon { } class lightningdragon extends dragon { } // 10 other one-headed dragon declarations here class hydra extends dragon { hydra() { anotherHead=new head(); for (int i=0;i<2;i++) { Heads.add(anotherHead); } } } class superhydra extends dragon { superhydra() { anotherHead=new head(); for (int i=0;i<4;i++) { Heads.add(anotherHead); } } }

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  • Prefer extension methods for encapsulation and reusability?

    - by tzaman
    edit4: wikified, since this seems to have morphed more into a discussion than a specific question. In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. (edit: Even in the current .NET library, I can see places where it would've been useful to have extensions instead of instance methods - for example, all of the utility functions of List<T> (Sort, BinarySearch, FindIndex, etc.) would be incredibly useful if they were lifted up to IList<T> - getting free bonus functionality like that adds a lot more benefit to implementing the interface.) So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself? (edit2: In response to Tomas - while C# did start out with Java's (overly, imo) OO mentality, it seems to be embracing more multi-paradigm programming with every new release; the main thrust of this question is whether using extension methods to drive a style change (towards more generic / functional C#) is useful or worthwhile..) edit3: overridable extension methods The only real problem identified so far with this approach, is that you can't specialize extension methods if you need to. I've been thinking about the issue, and I think I've come up with a solution. Suppose I have an interface MyInterface, which I want to extend - I define my extension methods in a MyExtension static class, and pair it with another interface, call it MyExtensionOverrider. MyExtension methods are defined according to this pattern: public static int MyMethod(this MyInterface obj, int arg, bool attemptCast=true) { if (attemptCast && obj is MyExtensionOverrider) { return ((MyExtensionOverrider)obj).MyMethod(arg); } // regular implementation here } The override interface mirrors all of the methods defined in MyExtension, except without the this or attemptCast parameters: public interface MyExtensionOverrider { int MyMethod(int arg); string MyOtherMethod(); } Now, any class can implement the interface and get the default extension functionality: public class MyClass : MyInterface { ... } Anyone that wants to override it with specific implementations can additionally implement the override interface: public class MySpecializedClass : MyInterface, MyExtensionOverrider { public int MyMethod(int arg) { //specialized implementation for one method } public string MyOtherMethod() { // fallback to default for others MyExtension.MyOtherMethod(this, attemptCast: false); } } And there we go: extension methods provided on an interface, with the option of complete extensibility if needed. Fully general too, the interface itself doesn't need to know about the extension / override, and multiple extension / override pairs can be implemented without interfering with each other. I can see three problems with this approach - It's a little bit fragile - the extension methods and override interface have to be kept synchronized manually. It's a little bit ugly - implementing the override interface involves boilerplate for every function you don't want to specialize. It's a little bit slow - there's an extra bool comparison and cast attempt added to the mainline of every method. Still, all those notwithstanding, I think this is the best we can get until there's language support for interface functions. Thoughts?

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  • Why can't I input the integers from a file?

    - by Anthony Glyadchenko
    I'm trying to get this C++ code to input a series of numbers from a text file: int x = 0; cin >> x; ifstream iffer; int numbers[12]; iffer.open("input.txt"); for (int i = 0; i < 12; i++){ iffer >> numbers[i]; } This doesn't seem to work on the Mac. Every cell will equal to 0 regardless of the values in the text file. In other words, the ifstream isn't assigning the numbers. How can I make this work? Is it a Mac issue and if so, how can I get it to work? Thanks! Anthony Glyadchenko

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  • Static initializer in Java

    - by Szere Dyeri
    My question is about one particular usage of static keyword. It is possible to use static keyword to cover a code block within a class which does not belong to any function. For example following code compiles: public class Test { private static final int a; static { a = 5; doSomething(a); } private static int doSomething(int x) { return (x+5); } } If you remove the static keyword it complains because the variable a is final. However it is possible to remove both final and static keywords and make it compile. It is confusing for me in both ways. How am I supposed to have a code section that does not belong to any method? How is it possible to invoke it? In general, what is the purpose of this usage? Or better, where can I find documentation about this?

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  • .NET: will Random.Random operate differently inside a static method

    - by Craig Johnston
    I am having difficulty with the following code which is inside a static method of a non-static class. int iRand; int rand; rand = new Random((int)DateTime.Now.Ticks); iRand = rand.Next(50000); The iRand number, along with some other values, are being inserted into a new row of an Access MDB table via OLEDB. The iRand number is being inserted into a field that is part of the primary key, and the insert attempt is throwing the following exception even though the iRand number is supposed to be random: System.Data.OleDb.OleDbException: The changes you requested to the table were not successful because they would create duplicate values in the index, primary key, or relationship. Change the data in the field or fields that contain duplicate data, remove the index, or redefine the index to permit duplicate entries and try again. Could the fact the method is static be making the iRand number stay the same, for some reason?

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  • What is the relationship between recursion functions and memory stack?

    - by Eslam
    is there's a direct relationship between recursive functions and the memory stack, for more explanation consider that code: public static int triangle(int n) { System.out.println(“Entering: n = ” + n); if (n == 1) { System.out.println(“Returning 1”); return 1; } else { int temp = n + triangle(n - 1); System.out.println(“Returning“ + temp); return temp; } }? in this example where will the values 2,3,4,5 be stored until the function returns ? note that they will be returned in LIFO(LastInFirstOut) is these a special case of recursion that deals with the memory stack or they always goes together?

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  • android circulate gallery iteration with 10 items.

    - by Faisal khan
    I am using the following customize gallery. I am having static 10 images, i want circulatery gallery which should circlate always should never ends after last item it should auto start by 1 or after first it should auto start from end. public class SizingGallery extends Gallery{ public SizingGallery(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected boolean getChildStaticTransformation(View child, Transformation t) { t.clear(); ImageView selectedChild = (ImageView)getSelectedView(); ImageView iv =(ImageView)child; BrowseMapCategoryRow cr = (BrowseMapCategoryRow)iv.getTag(); if (iv == selectedChild) { selectedChild.setImageResource(cr.getSelectedImgSrc()); }else{ iv.setImageResource(cr.getUnSelectedImgSrc()); } return true; } @Override protected int getChildDrawingOrder(int childCount, int i) { return super.getChildDrawingOrder(childCount, i); } }

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  • Can you call a SQL Stored Procedure that returns a record set and have those values loaded into vari

    - by codingguy3000
    Hello fellow stackers Please consider the following SQL Server table and stored procedure. create table customers(cusnum int, cusname varchar(50)) insert into customers(cusnum, cusname) values(1, 'Ken') insert into customers(cusnum, cusname) values (2, 'Violet') --The Wife create procedure getcus @cusnum int as Begin select cusname from customers (nolock) where cusnum = @cusnum End You know how you can write T-SQL code like this: declare @cusname varchar(50) select @cusname = cusname from customers where cusnum = 1 Can I do this with my stored procedure? for example the code would look like this: declare @cusnum int declare @cusname varchar(50) set @cusnum = 1 exec @cusname = cusname pbogetcus @cusnum Thanks in advance.

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