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  • In Ruby are there any related applications of the syntax: class << self ... end

    - by pez_dispenser
    class << self attr_accessor :n, :totalX, :totalY end The syntax above is used for defining class instance variables. But when I think about what syntax implies, it doesn't make any sense to me, so I'm wondering if this type of syntax is used for any other types of definitions. My point of confusion here is this: class << self The append operator normally means "add what's on the right to the object on the left". But in the context of this block, how does that add up to "put the contents of this block into the definition of the class instance rather than the instance"? For the same reason I'm confused as to why in one context class << self can define class instance variables while in another it seems to create class variables such as here: class Point # Instance methods go here class << self # Class methods go here end end

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  • C question: Padding bits in unsigned integers and bitwise operations (C89)

    - by Anonymous Question Guy
    I have a lot of code that performs bitwise operations on unsigned integers. I wrote my code with the assumption that those operations were on integers of fixed width without any padding bits. For example an array of 32 bit unsigned integers of which all 32 bits available for each integer. I'm looking to make my code more portable and I'm focused on making sure I'm C89 compliant (in this case). One of the issues that I've come across is possible padded integers. Take this extreme example, taken from the GMP manual: However on Cray vector systems it may be noted that short and int are always stored in 8 bytes (and with sizeof indicating that) but use only 32 or 46 bits. The nails feature can account for this, by passing for instance 8*sizeof(int)-INT_BIT. I've also read about this type of padding in other places. I actually read of a post on SO last night (forgive me, I don't have the link and I'm going to cite something similar from memory) where if you have, say, a double with 60 usable bits the other 4 could be used for padding and those padding bits could serve some internal purpose so they cannot be modified. So let's say for example my code is compiled on a platform where an unsigned int type is sized at 4 bytes, each byte being 8 bits, however the most significant 2 bits are padding bits. Would UINT_MAX in that case be 0x3FFFFFFF (1073741823) ? #include <stdio.h> #include <stdlib.h> /* padding bits represented by underscores */ int main( int argc, char **argv ) { unsigned int a = 0x2AAAAAAA; /* __101010101010101010101010101010 */ unsigned int b = 0x15555555; /* __010101010101010101010101010101 */ unsigned int c = a ^ b; /* ?? __111111111111111111111111111111 */ unsigned int d = c << 5; /* ?? __111111111111111111111111100000 */ unsigned int e = d >> 5; /* ?? __000001111111111111111111111111 */ printf( "a: %X\nb: %X\nc: %X\nd: %X\ne: %X\n", a, b, c, d, e ); return 0; } is it safe to XOR two integers with padding bits? wouldn't I XOR whatever the padding bits are? I can't find this behavior covered in C89. furthermore is the c var guaranteed to be 0x3FFFFFFF or if for example the two padding bits were both on in a or b would c be 0xFFFFFFFF ? same question with d and e. am i manipulating the padding bits by shifting? I would expect to see this below, assuming 32 bits with the 2 most significant bits used for padding, but I want to know if something like this is guaranteed: a: 2AAAAAAA b: 15555555 c: 3FFFFFFF d: 3FFFFFE0 e: 01FFFFFF Also are padding bits always the most significant bits or could they be the least significant bits? Thanks guys EDIT 12/19/2010 5PM EST: Christoph has answered my question. Thanks! I had also asked (above) whether padding bits are always the most significant bits. This is cited in the rationale for the C99 standard, and the answer is no. I am playing it safe and assuming the same for C89. Here is specifically what the C99 rationale says for §6.2.6.2 (Representation of Integer Types): Padding bits are user-accessible in an unsigned integer type. For example, suppose a machine uses a pair of 16-bit shorts (each with its own sign bit) to make up a 32-bit int and the sign bit of the lower short is ignored when used in this 32-bit int. Then, as a 32-bit signed int, there is a padding bit (in the middle of the 32 bits) that is ignored in determining the value of the 32-bit signed int. But, if this 32-bit item is treated as a 32-bit unsigned int, then that padding bit is visible to the user’s program. The C committee was told that there is a machine that works this way, and that is one reason that padding bits were added to C99. Footnotes 44 and 45 mention that parity bits might be padding bits. The committee does not know of any machines with user-accessible parity bits within an integer. Therefore, the committee is not aware of any machines that treat parity bits as padding bits. EDIT 12/28/2010 3PM EST: I found an interesting discussion on comp.lang.c from a few months ago. Bitwise Operator Effects on Padding Bits (VelocityReviews reader) Bitwise Operator Effects on Padding Bits (Google Groups alternate link) One point made by Dietmar which I found interesting: Let's note that padding bits are not necessary for the existence of trap representations; combinations of value bits which do not represent a value of the object type would also do.

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  • Compare two String with MySQL

    - by Scorpi0
    Hi, I wan't to compare two strings in a SQL request so I can retrieve the best match, the aim is to propose to an operator the best zip code possible. For example, in France, we have Integer Zip code, so I made an easy request : SELECT * FROM myTable ORDER BY abs(zip_code - 75000) This request returns first the data closest of Paris. Unfortunatelly, United Kingdom have zip code like AB421RS, so my request can't do it. I see in SQL Server a function 'Difference' : http://www.java2s.com/Code/SQLServer/String-Functions/DIFFERENCEworkoutwhenonestringsoundssimilartoanotherstring.htm But I use MySQL.. Is there anyone who have a good idea to do the trick in one simple request ? PS : the Levenshtein Distance will not do it, as I really wan't to compare string like if they were number. ABCDEF have to be closer to AWXYZ than to ZBCDEF.

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  • Memory leak in Qt signal and slots

    - by Ajay
    Hello, I am running valgrind on my Qt code,and even on successful exit of the application, get the following report from valgrind 8,832 bytes in 92 blocks are still reachable in loss record 12 of 12 at 0x4025390: operator new(unsigned int) (vg_replace_malloc.c:214) ==3339== by 0x4B75F05: QMutex::QMutex(QMutex::RecursionMode) (qmutex.cpp:123) ==3339== by 0x4B77602: QMutexPool::get(void const*) (qmutexpool.cpp:137) ==3339== by 0x4CA0EC2: signalSlotLock(QObject const*) (qobject.cpp:112) ==3339== by 0x4CA3939: QMetaObjectPrivate::connect(QObject const*, int, QObject const*, int, int, int*) (qobject.cpp:2900) ==3339== by 0x4CA5C00: QObject::connect(QObject const*, char const*, QObject const*, char const*, Qt::ConnectionType) (qobject.cpp:2599) I disconnect all signal connections and also delete the objects. The above mentioned leak increases if i increase the amount of signal and slot connections? Can anybody help with this?

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  • LINQ Searching Only Allowing Equivalency

    - by Mad Halfling
    Hi folks, I'm trying to filter a set of records based on a sub-object's criteria. This compiles ok recordList = recordList.Where(r => r.Areas.Where(a => a.Area == "Z").Count() > 0); but this doesn't recordList = recordList.Where(r => r.Areas.Where(a => a.Area <= "Z").Count() > 0); giving these errors Cannot convert lambda expression to type 'string' because it is not a delegate type Delegate 'System.Func' does not take '1' arguments Operator '<=' cannot be applied to operands of type 'string' and 'string' != works ok, by any sort of less than or greater than operation fails.

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  • What does this xkcd code do?

    - by cobbal
    On the xkcd site today, the following appeared as a joke in a <script language="scheme"> tag so what does the following code do / represent? (define (eval exp env) (cond ((self-evaluating? exp) exp) ((variable? exp) (lookup-variable-value exp env)) ((quoted? exp) (text-of-quotation exp)) ((assignment? exp) (eval-assignment exp env)) ((definition? exp) (eval-definition exp env)) ((if? exp) (eval-if exp env)) ((lambda? exp) (make-procedure (lambda-parameters exp) (lambda-body exp) env)) ((begin? exp) (eval-sequence (begin-actions exp) env)) ((cond? exp) (eval (cond->if exp) env)) ((application? exp) (apply (eval (operator exp) env) (list-of-values (operands exp) env))) (else (error "Common Lisp or Netscape Navigator 4.0+ Required" exp))))

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  • Using local classes with STL algorithms

    - by David Rodríguez - dribeas
    I have always wondered why you cannot use locally defined classes as predicates to STL algorithms. In the question: Approaching STL algorithms, lambda, local classes and other approaches, BubbaT mentions says that 'Since the C++ standard forbids local types to be used as arguments' Example code: int main() { int array[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; std::vector<int> v( array, array+10 ); struct pair : public std::unary_function<int,bool> { bool operator()( int x ) { return !( x % 2 ); } }; std::remove_if( v.begin(), v.end(), pair() ); // error } Does anyone know where in the standard is the restriction? What is the rationale for disallowing local types?

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  • Shorthand for nested null checking C#

    - by Myster
    As far as I know there is not a significantly more elegant way to write the following.... string src; if((ParentContent!= null) &&(ParentContent.Image("thumbnail") != null) &&(ParentContent.Image("thumbnail").Property("src") != null)) src = ParentContent.Image("thumbnail").Property("src").Value Do you think there should be a C# language feature to make this shorter? And if so, what should it look like? for example, something like extending the ?? operator string src = ParentContent??.Image("thumbnail")??.Property("width")??.Value; Apologies for the rather contrived example, and my over-simplified solution.

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  • Problem while running the j2me application

    - by Paru
    I am not able to view any content in the emulator while running the application. The Build is not failed and i am able run the application successfully. While i am closing the emulator i am getting an error. i can provide both code and log here. import javax.microedition.lcdui.; import javax.microedition.midlet.; import java.io.; import java.lang.; import javax.microedition.io.; import javax.microedition.rms.; public class Login extends MIDlet implements CommandListener { TextField ItemName=null; TextField ItemNo=null; TextField UserName=null; TextField Password=null; Form authForm,mainscreen; TextBox t = null; StringBuffer b = new StringBuffer(); private Display myDisplay = null; private Command okCommand = new Command("Login", Command.OK, 1); private Command exitCommand = new Command("Exit", Command.EXIT, 2); private Command sendCommand = new Command("Send", Command.OK, 1); private Command backCommand = new Command("Back", Command.BACK, 2); private Alert alert = null; public Login() { ItemName=new TextField("Item Name","",10,TextField.ANY); ItemNo=new TextField("Item No","",10,TextField.ANY); myDisplay = Display.getDisplay(this); UserName=new TextField("Your Name","",10,TextField.ANY); Password=new TextField("Password","",10,TextField.PASSWORD); authForm=new Form("Identification"); mainscreen=new Form("Logging IN"); mainscreen.addCommand(sendCommand); mainscreen.addCommand(backCommand); authForm.append(UserName); authForm.append(Password); authForm.addCommand(okCommand); authForm.addCommand(exitCommand); authForm.setCommandListener(this); myDisplay.setCurrent(authForm); } public void startApp() throws MIDletStateChangeException { } public void pauseApp() { } protected void destroyApp(boolean unconditional) throws MIDletStateChangeException { } public void commandAction(Command c, Displayable d) { if ((c == okCommand) && (d == authForm)) { if (UserName.getString().equals("") || Password.getString().equals("")){ alert = new Alert("Error", "You should enter Username and Password", null, AlertType.ERROR); alert.setTimeout(Alert.FOREVER); myDisplay.setCurrent(alert); } else{ //myDisplay.setCurrent(mainscreen); login(UserName.getString(),Password.getString()); } } if ((c == backCommand) && (d == mainscreen)) { myDisplay.setCurrent(authForm); } if ((c == exitCommand) && (d == authForm)) { notifyDestroyed(); } if ((c == sendCommand) && (d == mainscreen)) { if(ItemName.getString().equals("") || ItemNo.getString().equals("")){ } else{ sendItem(ItemName.getString(),ItemNo.getString()); } } } public void login(String UserName,String PassWord) { HttpConnection connection=null; DataInputStream in=null; String url="http://olario.net/submitpost/submitpost/login.php"; OutputStream out=null; try { connection=(HttpConnection)Connector.open(url); connection.setRequestMethod(HttpConnection.POST); connection.setRequestProperty("IF-Modified-Since", "2 Oct 2002 15:10:15 GMT"); connection.setRequestProperty("User-Agent","Profile/MIDP-1.0 Configuration/CLDC-1.0"); connection.setRequestProperty("Content-Language", "en-CA"); connection.setRequestProperty("Content-Length",""+ (UserName.length()+PassWord.length())); connection.setRequestProperty("username",UserName); connection.setRequestProperty("password",PassWord); out = connection.openDataOutputStream(); out.flush(); in = connection.openDataInputStream(); int ch; while((ch = in.read()) != -1) { b.append((char) ch); //System.out.println((char)ch); } //t = new TextBox("Reply",b.toString(),1024,0); //mainscreen.append(b.toString()); String auth=b.toString(); if(in!=null) in.close(); if(out!=null) out.close(); if(connection!=null) connection.close(); if(auth.equals("ok")){ mainscreen.setCommandListener(this); myDisplay.setCurrent(mainscreen); } } catch(IOException x){ } } public void sendItem(String itemname,String itemno){ HttpConnection connection=null; DataInputStream in=null; String url="http://www.olario.net/submitpost/submitpost/submitPost.php"; OutputStream out=null; try { connection=(HttpConnection)Connector.open(url); connection.setRequestMethod(HttpConnection.POST); connection.setRequestProperty("IF-Modified-Since", "2 Oct 2002 15:10:15 GMT"); connection.setRequestProperty("User-Agent","Profile/MIDP-1.0 Configuration/CLDC-1.0"); connection.setRequestProperty("Content-Language", "en-CA"); connection.setRequestProperty("Content-Length",""+ (itemname.length()+itemno.length())); connection.setRequestProperty("itemCode",itemname); connection.setRequestProperty("qty",itemno); out = connection.openDataOutputStream(); out.flush(); in = connection.openDataInputStream(); int ch; while((ch = in.read()) != -1) { b.append((char) ch); //System.out.println((char)ch); } //t = new TextBox("Reply",b.toString(),1024,0); //mainscreen.append(b.toString()); String send=b.toString(); if(in!=null) in.close(); if(out!=null) out.close(); if(connection!=null) connection.close(); if(send.equals("added")){ alert = new Alert("Error", "Send Successfully", null, AlertType.INFO); alert.setTimeout(Alert.FOREVER); myDisplay.setCurrent(alert); } } catch(IOException x){ } } } and the log is pre-init: pre-load-properties: exists.config.active: exists.netbeans.user: exists.user.properties.file: load-properties: exists.platform.active: exists.platform.configuration: exists.platform.profile: basic-init: cldc-pre-init: cldc-init: cdc-init: ricoh-pre-init: ricoh-init: semc-pre-init: semc-init: savaje-pre-init: savaje-init: sjmc-pre-init: sjmc-init: ojec-pre-init: ojec-init: cdc-hi-pre-init: cdc-hi-init: nokiaS80-pre-init: nokiaS80-init: nsicom-pre-init: nsicom-init: post-init: init: conditional-clean-init: conditional-clean: deps-jar: pre-preprocess: do-preprocess: Pre-processing 0 file(s) into /home/sreekumar/NetBeansProjects/Login/build/preprocessed directory. post-preprocess: preprocess: pre-compile: extract-libs: do-compile: post-compile: compile: pre-obfuscate: proguard-init: skip-obfuscation: proguard: post-obfuscate: obfuscate: lwuit-build: pre-preverify: do-preverify: post-preverify: preverify: pre-jar: set-password-init: set-keystore-password: set-alias-password: set-password: create-jad: add-configuration: add-profile: do-extra-libs: nokiaS80-prepare-j9: nokiaS80-prepare-manifest: nokiaS80-prepare-manifest-no-icon: nokiaS80-create-manifest: jad-jsr211-properties.check: jad-jsr211-properties: semc-build-j9: do-jar: nsicom-create-manifest: do-jar-no-manifest: update-jad: Updating application descriptor: /home/sreekumar/NetBeansProjects/Login/dist/Login.jad Generated "/home/sreekumar/NetBeansProjects/Login/dist/Login.jar" is 3501 bytes. sign-jar: ricoh-init-dalp: ricoh-add-app-icon: ricoh-build-dalp-with-icon: ricoh-build-dalp-without-icon: ricoh-build-dalp: savaje-prepare-icon: savaje-build-jnlp: post-jar: jar: pre-run: netmon.check: open-netmon: cldc-run: Copying 1 file to /home/sreekumar/NetBeansProjects/Login/dist/nbrun4244989945642509378 Copying 1 file to /home/sreekumar/NetBeansProjects/Login/dist/nbrun4244989945642509378 Jad URL for OTA execution: http://localhost:8082/servlet/org.netbeans.modules.mobility.project.jam.JAMServlet//home/sreekumar/NetBeansProjects/Login/dist//Login.jad Starting emulator in execution mode Running with storage root /home/sreekumar/j2mewtk/2.5.2/appdb/temp.DefaultColorPhone1 /home/sreekumar/NetBeansProjects/Login/nbproject/build-impl.xml:915: Execution failed with error code 143. BUILD FAILED (total time: 35 seconds)

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  • ruby syntactic sugar: dealing with nils..

    - by luca
    probably asked already but I couldn't find it.. here are 2 common situation (for me while programming rails..) that are frustrating to write in ruby: "a string".match(/abc(.+)abc/)[1] in this case I get an error because the string doesn't match, therefore the [] operator is called upon nil. What I'd like to find is a nicer alternative to the following: temp="a string".match(/abc(.+)abc/); temp.nil? ? nil : temp[1] in brief, if it didn't match simply return nil without the error The second situation is this one: var = something.very.long.and.tedious.to.write var = something.other if var.nil? In this case I want to assign something to var only if it's not nil, in case it's nil I'll assign something.other.. Any suggestion? Thanks!

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  • Concurrent Generation of Sequential Keys

    - by GenTiradentes
    I'm working on a project which generates a very large number of sequential text strings, in a very tight loop. My application makes heavy use of SIMD instruction set extensions like SSE and MMX, in other parts of the program, but the key generator is plain C++. The way my key generator works is I have a keyGenerator class, which holds a single char array that stores the current key. To get the next key, there is a function called "incrementKey," which treats the string as a number, adding one to the string, carrying where necessary. Now, the problem is, the keygen is somewhat of a bottleneck. It's fast, but it would be nice if it were faster. One of the biggest problems is that when I'm generating a set of sequential keys to be processed using my SSE2 code, I have to have the entire set stored in an array, which means I have to sequentially generate and copy 12 strings into an array, one by one, like so: char* keys[12]; for(int i = 0; i < 12; i++) { keys[i] = new char[16]; strcmp(keys[i], keygen++); } So how would you efficiently generate these plaintext strings in order? I need some ideas to help move this along. Concurrency would be nice; as my code is right now, each successive key depends on the previous one, which means that the processor can't start work on the next key until the current one has been completely generated. Here is the code relevant to the key generator: KeyGenerator.h class keyGenerator { public: keyGenerator(unsigned long long location, characterSet* charset) : location(location), charset(charset) { for(int i = 0; i < 16; i++) key[i] = 0; charsetStr = charset->getCharsetStr(); integerToKey(); } ~keyGenerator() { } inline void incrementKey() { register size_t keyLength = strlen(key); for(register char* place = key; place; place++) { if(*place == charset->maxChar) { // Overflow, reset char at place *place = charset->minChar; if(!*(place+1)) { // Carry, no space, insert char *(place+1) = charset->minChar; ++keyLength; break; } else { continue; } } else { // Space available, increment char at place if(*place == charset->charSecEnd[0]) *place = charset->charSecBegin[0]; else if(*place == charset->charSecEnd[1]) *place = charset->charSecBegin[1]; (*place)++; break; } } } inline char* operator++() // Pre-increment { incrementKey(); return key; } inline char* operator++(int) // Post-increment { memcpy(postIncrementRetval, key, 16); incrementKey(); return postIncrementRetval; } void integerToKey() { register unsigned long long num = location; if(!num) { key[0] = charsetStr[0]; } else { num++; while(num) { num--; unsigned int remainder = num % charset->length; num /= charset->length; key[strlen(key)] = charsetStr[remainder]; } } } inline unsigned long long keyToInteger() { // TODO return 0; } inline char* getKey() { return key; } private: unsigned long long location; characterSet* charset; std::string charsetStr; char key[16]; // We need a place to store the key for the post increment operation. char postIncrementRetval[16]; }; CharacterSet.h struct characterSet { characterSet() { } characterSet(unsigned int len, int min, int max, int charsec0, int charsec1, int charsec2, int charsec3) { init(length, min, max, charsec0, charsec1, charsec2, charsec3); } void init(unsigned int len, int min, int max, int charsec0, int charsec1, int charsec2, int charsec3) { length = len; minChar = min; maxChar = max; charSecEnd[0] = charsec0; charSecBegin[0] = charsec1; charSecEnd[1] = charsec2; charSecBegin[1] = charsec3; } std::string getCharsetStr() { std::string retval; for(int chr = minChar; chr != maxChar; chr++) { for(int i = 0; i < 2; i++) if(chr == charSecEnd[i]) chr = charSecBegin[i]; retval += chr; } return retval; } int minChar, maxChar; // charSec = character set section int charSecEnd[2], charSecBegin[2]; unsigned int length; };

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  • Passing unknown classes to String Streams in C++

    - by Sqeaky
    I am using a template function and I am passing and I may be sending instances of a variety of classes to a string stream. What can I do to make sure this continues to work? Let me be more specific where do I define the behavior for this? Is there some member that should be on each class being sent to the string stream, should I in some enhance or extend the existing String stream (I was thinking building a class that inherits from sstream and overloads the << operator to handle all the possible classes)? I had trouble even finding documentation on this, so even links to more resources would be helpful.

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  • What does !! (double exclamation point) mean?

    - by molecules
    In the code below, from a blog post by Alias, I noticed the use of the double exclamation point !!. I was wondering what it meant and where I could go in the future to find explanations for Perl syntax like this. (Yes, I already searched for '!!' at perlsyn). package Foo; use vars qw{$DEBUG}; BEGIN { $DEBUG = 0 unless defined $DEBUG; } use constant DEBUG => !! $DEBUG; sub foo { debug('In sub foo') if DEBUG; ... } UPDATE Thanks for all of your answers. Here is something else I just found that is related The List Squash Operator x!!

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  • Compile time string hashing

    - by Caspin
    I have read in few different places that using c++0x's new string literals it might be possible to compute a string's hash at compile time. However, no one seems to be ready to come out and say that it will be possible or how it would be done. Is this possible? What would the operator look like? I'm particularly interested use cases like this. void foo( const std::string& value ) { switch( std::hash(value) ) { case "one"_hash: one(); break; case "two"_hash: two(); break; /*many more cases*/ default: other(); break; } } Note: the compile time hash function doesn't have to look exactly as I've written it. I did my best to guess what the final solution would look like, but meta_hash<"string"_meta>::value could also be a viable solution.

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  • Linq to sql translation to sql of custom method

    - by DJPB
    hi there is there a way to translate an expression to sql to use with linq to sql? for example I have a method that compares two values example: MyComparer.Compare(value1, value2, ">") return value1 > value2 MyComparer.Compare(value1, value2, "=") return value1 == value2 MyComparer.Compare(value1, value2, "<=") return value1 <= value2 and i would like a query like var list = from i in dataContext.items where MyComparer.Compare(i.value, someValue, "some operator") select ... this won't work because, obviously, MyComparer doesn't translate to sql maybe this is a twisted question, but how can i translate this method to sql or is this possible? tks

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  • Load binary file using fstream

    - by Kirill V. Lyadvinsky
    I'm trying to load binary file using fstream in the following way: #include <iostream #include <fstream #include <iterator #include <vector using namespace std; int main() { basic_fstream<uint32_t file( "somefile.dat", ios::in|ios::binary ); vector<uint32_t buffer; buffer.assign( istream_iterator<uint32_t, uint32_t( file ), istream_iterator<uint32_t, uint32_t() ); cout << buffer.size() << endl; return 0; } But it doesn't work. In Ubuntu it crashed with std::bad_cast exception. In MSVC++ 2008 it just prints 0. I know that I could use file.read to load file, but I want to use iterator and operator>> to load parts of the file. Is that possible? Why the code above doesn't work?

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  • Java 'Prototype' pattern - new vs clone vs class.newInstance

    - by Guillaume
    In my project there are some 'Prototype' factories that create instances by cloning a final private instance. The author of those factories says that this pattern provides better performance than calling 'new' operator. Using google to get some clues about that, I've found nothing really relevant about that. Here is a small excerpt found in a javdoc from an unknown project javdoc from an unknown project Sadly, clone() is rather slower than calling new. However it is a lot faster than calling java.lang.Class.newInstance(), and somewhat faster than rolling our own "cloner" method. For me it's looking like an old best practice of the java 1.1 time. Does someone know more about this ? Is this a good practice to use that with 'modern' jvm ?

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  • UITableview has problem reloading

    - by seelani
    Hi guys, I've kinda finished my application for a school project but have run into a major "bug". It's a account management application. I'm unable to insert a picture here so here's a link: http://i232.photobucket.com/albums/ee112/seelani/Screenshot2010-12-22atPM075512.png Here's the problem when i click on the plus sign, i push a nav controller to load another view to handle the adding and deleting of categories. When i add and return back to the view above, it doesn't update. It only updates after i hit the button on the right which is another view used to change some settings, and return back to the page. I did some research on viewWillAppear and such but I'm still confused to why it doesn't work properly. This problem is also affecting my program when i delete a category, and return back to this view it crashes cos the view has not reloaded successfully. I will get this error when deleting and returning to the view. "* Terminating app due to uncaught exception 'NSRangeException', reason: '* -[NSMutableArray objectAtIndex:]: index 4 beyond bounds [0 .. 3]'". [EDIT] Table View Code: @class LoginViewController; @implementation CategoryTableViewController @synthesize categoryTableViewController; @synthesize categoryArray; @synthesize accountsTableViewController; @synthesize editAccountTable; @synthesize window; CategoryMgmtTableController *categoryMgmtTableController; ChangePasswordView *changePasswordView; - (void) save_Clicked:(id)sender { /* UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Category Management" message:@"Load category management table view" delegate:self cancelButtonTitle: @"OK" otherButtonTitles:nil]; [alert show]; [alert release]; */ KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate]; categoryMgmtTableController = [[CategoryMgmtTableController alloc]initWithNibName:@"CategoryMgmtTable" bundle:nil]; [appDelegate.categoryNavController pushViewController:categoryMgmtTableController animated:YES]; } - (void) change_Clicked:(id)sender { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Change Password" message:@"Change password View" delegate:self cancelButtonTitle: @"OK" otherButtonTitles:nil]; [alert show]; [alert release]; KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate]; changePasswordView = [[ChangePasswordView alloc]initWithNibName:@"ChangePasswordView" bundle:nil]; [appDelegate.categoryNavController pushViewController:changePasswordView animated:YES]; /* KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate]; categoryMgmtTableController = [[CategoryMgmtTableController alloc]initWithNibName:@"CategoryMgmtTable" bundle:nil]; [appDelegate.categoryNavController pushViewController:categoryMgmtTableController animated:YES]; */ } #pragma mark - #pragma mark Initialization /* - (id)initWithStyle:(UITableViewStyle)style { // Override initWithStyle: if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad. if ((self = [super initWithStyle:style])) { } return self; } */ -(void) initializeCategoryArray { sqlite3 *db= [KeyCryptAppAppDelegate getNewDBConnection]; KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate]; const char *sql = [[NSString stringWithFormat:(@"Select Category from Categories;")]cString]; const char *cmd = [[NSString stringWithFormat:@"pragma key = '%@' ", appDelegate.pragmaKey]cString]; sqlite3_stmt *compiledStatement; sqlite3_exec(db, cmd, NULL, NULL, NULL); if (sqlite3_prepare_v2(db, sql, -1, &compiledStatement, NULL)==SQLITE_OK) { while(sqlite3_step(compiledStatement) == SQLITE_ROW) [categoryArray addObject:[NSString stringWithUTF8String:(char*) sqlite3_column_text(compiledStatement, 0)]]; } else { NSAssert1(0,@"Error preparing statement", sqlite3_errmsg(db)); } sqlite3_finalize(compiledStatement); } #pragma mark - #pragma mark View lifecycle - (void)viewDidLoad { // Uncomment the following line to display an Edit button in the navigation bar for this view controller. // self.navigationItem.rightBarButtonItem = self.editButtonItem; [super viewDidLoad]; } - (void)viewWillAppear:(BOOL)animated { self.title = NSLocalizedString(@"Categories",@"Types of Categories"); categoryArray = [[NSMutableArray alloc]init]; [self initializeCategoryArray]; self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(save_Clicked:)] autorelease]; self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAction target:self action:@selector(change_Clicked:)] autorelease]; [super viewWillAppear:animated]; } - (void)viewDidAppear:(BOOL)animated { NSLog (@"view did appear"); [super viewDidAppear:animated]; } - (void)viewWillDisappear:(BOOL)animated { NSLog (@"view will disappear"); [super viewWillDisappear:animated]; } - (void)viewDidDisappear:(BOOL)animated { [categoryTableView reloadData]; NSLog (@"view did disappear"); [super viewDidDisappear:animated]; } /* // Override to allow orientations other than the default portrait orientation. - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { // Return YES for supported orientations return (interfaceOrientation == UIInterfaceOrientationPortrait); } */ #pragma mark - #pragma mark Table view data source - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { // Return the number of sections. return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // Return the number of rows in the section. return [self.categoryArray count]; } // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } // Configure the cell... NSUInteger row = [indexPath row]; cell.text = [categoryArray objectAtIndex:row]; cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator; return cell; } /* // Override to support conditional editing of the table view. - (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the specified item to be editable. return YES; } */ /* // Override to support editing the table view. - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the row from the data source [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES]; } else if (editingStyle == UITableViewCellEditingStyleInsert) { // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view } } */ /* // Override to support rearranging the table view. - (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath { } */ /* // Override to support conditional rearranging of the table view. - (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the item to be re-orderable. return YES; } */ #pragma mark - #pragma mark Table view delegate - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSString *selectedCategory = [categoryArray objectAtIndex:[indexPath row]]; NSLog (@"AccountsTableView.xib is called."); if ([categoryArray containsObject: selectedCategory]) { if (self.accountsTableViewController == nil) { AccountsTableViewController *aAccountsView = [[AccountsTableViewController alloc]initWithNibName:@"AccountsTableView"bundle:nil]; self.accountsTableViewController =aAccountsView; [aAccountsView release]; } NSInteger row =[indexPath row]; accountsTableViewController.title = [NSString stringWithFormat:@"%@", [categoryArray objectAtIndex:row]]; // This portion pushes the categoryNavController. KeyCryptAppAppDelegate *delegate = [[UIApplication sharedApplication] delegate]; [self.accountsTableViewController initWithTextSelected:selectedCategory]; KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate]; appDelegate.pickedCategory = selectedCategory; [delegate.categoryNavController pushViewController:accountsTableViewController animated:YES]; } } #pragma mark - #pragma mark Memory management - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Relinquish ownership any cached data, images, etc that aren't in use. } - (void)viewDidUnload { // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand. // For example: self.myOutlet = nil; } - (void)dealloc { [accountsTableViewController release]; [super dealloc]; } @end And the code that i used to delete rows(this is in a totally different tableview): - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the row from the data source NSString *selectedCategory = [categoryArray objectAtIndex:indexPath.row]; [categoryArray removeObjectAtIndex:indexPath.row]; [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES]; [deleteCategoryTable reloadData]; //NSString *selectedCategory = [categoryArray objectAtIndex:indexPath.row]; sqlite3 *db= [KeyCryptAppAppDelegate getNewDBConnection]; KeyCryptAppAppDelegate *appDelegate = (KeyCryptAppAppDelegate *)[[UIApplication sharedApplication] delegate]; const char *sql = [[NSString stringWithFormat:@"Delete from Categories where Category = '%@';", selectedCategory]cString]; const char *cmd = [[NSString stringWithFormat:@"pragma key = '%@' ", appDelegate.pragmaKey]cString]; sqlite3_stmt *compiledStatement; sqlite3_exec(db, cmd, NULL, NULL, NULL); if (sqlite3_prepare_v2(db, sql, -1, &compiledStatement, NULL)==SQLITE_OK) { sqlite3_exec(db,sql,NULL,NULL,NULL); } else { NSAssert1(0,@"Error preparing statement", sqlite3_errmsg(db)); } sqlite3_finalize(compiledStatement); } else if (editingStyle == UITableViewCellEditingStyleInsert) { // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view } }

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  • How do I copy object in Qt?

    - by Martin
    I'm using Qt and have some real basic problems. I have created my own widget MyTest that have a variable obj. I need to set this variable obj from an object outside of the widget so that the variable is copied not just a pointer to another object. I get an error message and can't figure out how to do this basic stuff. This is the code I'm using: MyTest.h: class MyTest : public QWidget { Q_OBJECT public: void setObj(QObject &inobj); QObject obj; .... } MyTest.cpp: void MyTest::setObj(QObject &inobj) { obj = inobj; //HERE I get the error message: "illegal access from 'QObject' to protected/private member 'QObject::operator=(const QObject &)'" } main.cpp: int main(int argc, char *argv[]) { QApplication a(argc, argv); QObject *ob = new QObject(); MyTest w; w.setObj(*ob); } Thanks for your help!

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  • How to make Databinding type safe and support refactoring

    - by Ian Ringrose
    When I wish to bind a control to a property of my object, I have to provide the name of the property as a string. This is not very good because: If the property is removed or renamed, I don’t get a compiler warning. If a rename the property with a refactoring tool, it is likely the data binding will not be updated. I don’t get an error until runtime if the type of the property is wrong, e.g. binding an integer to a date chooser. Is there a design-paten that gets round this, but still has the ease of use of data-binding? (This is a problem in WinForm, Asp.net and WPF and most likely lots of other systems) I have now found "workarounds for nameof() operator in C#: typesafe databinding" that also has a good starting point for a solution.

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  • R: ggplot2, how to add a number of layers to a plot at once to reduce code

    - by John
    library(ggplot2) This code produces a nice looking plot: qplot(cty, hwy, data = mpg, colour = displ) + scale_y_log2() + labs(x="x axis") + labs(y="y axis") + opts(title = "my title") But I want to setup variables to try and to reduce code repetition: log_scale <- scale_y_log2() xscale <- labs(x="x axis") yscale <- labs(y="y axis") title <- opts(title = "my title") my_scales <- c(log_scale, xscale, yscale, title) # make a variable to hold the scale info changes above So that I can do this and add a bunch of things at the same time: qplot(cty, hwy, data = mpg, colour = displ) + my_scales # add these to your plot. but I get this error: Error in object$class : $ operator is invalid for atomic vectors I realize that the things going into my_scales need to be layers / different types of objects, but I don't see what they should be.

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  • Practical differences between classes and structs in .net (not conceptual)?

    - by Gulshan
    Whenever I tried to search about differences between classes and structs in C# or .net, I ended up with the conceptual overview of the two things like value type or the reference type, where the variables are allocated etc. But I need some practical differences. I have found some like different behavior of assignment operator, having constructors etc. Can anybody provide some more practical differences which will be directly useful while coding? Like the things works with one but not with other or same operation showing different behavior. And some common mistakes regarding these two. Also please suggest where to consider using a struct instead of a class. And where the structs should not be used.

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  • Error while excuting a simple boost thread program

    - by Eternal Learner
    Hi All, Could you tell mw what is the problem with the below boost::thread program #include<iostream> #include<boost/thread/thread.hpp> boost::mutex mutex; class A { public: A() : a(0) {} void operator()() { boost::mutex::scoped_lock lock(mutex); } private: int a; }; int main() { boost::thread thr1(A()); boost::thread thr2(A()); thr1.join(); thr2.join(); } I get the error message: error: request for member 'join' in 'thr1', which is of non-class type 'boost::thread()(A ()())' BoostThread2.cpp:30: error: request for member 'join' in 'thr2', which is of non-class type 'boost::thread ()(A ()())'

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