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  • Compile error with initializer_list when trying to use it to initialize member value of class

    - by ilektron
    I am trying to make a class initializable from an initialization_list in a class constructor's constructor's initialization list. It works for a std::map, but not for my custom class. I don't see any difference other than templates are used in std::map. #include <iostream> #include <initializer_list> #include <string> #include <sstream> #include <map> using std::string; class text_thing { private: string m_text; public: text_thing() { } text_thing(text_thing& other); text_thing(std::initializer_list< std::pair<const string, const string> >& il); text_thing& operator=(std::initializer_list< std::pair<const string, const string> >& il); operator string() { return m_text; } }; class static_base { private: std::map<string, string> m_test_map; text_thing m_thing; static_base(); public: static static_base& getInstance() { static static_base instance; return instance; } string getText() { return (string)m_thing; } }; typedef std::pair<const string, const string> spair; text_thing::text_thing(text_thing& other) { m_text = other.m_text; } text_thing::text_thing(std::initializer_list< std::pair<const string, const string> >& il) { std::stringstream text_gen; for (auto& apair : il) { text_gen << "{" << apair.first << ", " << apair.second << "}" << std::endl; } } text_thing& text_thing::operator=(std::initializer_list< std::pair<const string, const string> >& il) { std::stringstream text_gen; for (auto& apair : il) { text_gen << "{" << apair.first << ", " << apair.second << "}" << std::endl; } return *this; } static_base::static_base() : m_test_map{{"test", "1"}, {"test2", "2"}}, // Compiler fine with this m_thing{{"test", "1"}, {"test2", "2"}} // Compiler doesn't like this { } int main() { std::cout << "Starting the program" << std::endl; std::cout << "The text thing: " << std::endl << static_base::getInstance().getText(); } I get this compiler output g++ -O0 -g3 -Wall -c -fmessage-length=0 -std=c++11 -MMD -MP -MF"static_base.d" -MT"static_base.d" -o "static_base.o" "../static_base.cpp" Finished building: ../static_base.cpp Building file: ../test.cpp Invoking: GCC C++ Compiler g++ -O0 -g3 -Wall -c -fmessage-length=0 -std=c++11 -MMD -MP -MF"test.d" -MT"test.d" -o "test.o" "../test.cpp" ../test.cpp: In constructor ‘static_base::static_base()’: ../test.cpp:94:40: error: no matching function for call to ‘text_thing::text_thing(<brace-enclosed initializer list>)’ m_thing{{"test", "1"}, {"test2", "2"}} ^ ../test.cpp:94:40: note: candidates are: ../test.cpp:72:1: note: text_thing::text_thing(std::initializer_list<std::pair<const std::basic_string<char>, const std::basic_string<char> > >&) text_thing::text_thing(std::initializer_list< std::pair<const string, const string> >& il) ^ ../test.cpp:72:1: note: candidate expects 1 argument, 2 provided ../test.cpp:67:1: note: text_thing::text_thing(text_thing&) text_thing::text_thing(text_thing& other) ^ ../test.cpp:67:1: note: candidate expects 1 argument, 2 provided ../test.cpp:23:2: note: text_thing::text_thing() text_thing() ^ ../test.cpp:23:2: note: candidate expects 0 arguments, 2 provided make: *** [test.o] Error 1 Output of gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.1-2ubuntu1~13.04' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 4.8.1 (Ubuntu 4.8.1-2ubuntu1~13.04) It compiles fine with the std::map constructed this way, and if I modify the static_base to return the strings from the maps, all is fine and dandy. Please help me understand what is going on here.

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  • sendmessage mouseevent not working

    - by kevin
    I have this code: Private Const MOUSEEVENTF_LEFTDOWN = &H2 Private Const MOUSEEVENTF_LEFTUP = &H4 Dim WindowHandle As Long = FindWindow(vbNullString, "Ultima Online") SendMessage(WindowHandle, MOUSEEVENTF_LEFTDOWN, 0, 0) SendMessage(WindowHandle, MOUSEEVENTF_LEFTUP, 0, 0) I know it is getting the windowhandle fine, because I made a conditional statment that pops up a messagebox if windowhandle = 0 The problem is that it is not sending the mouse click to the window.

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  • Overriding an ActiveRecord attribute

    - by jspooner
    I have a model with a completed:boolean column that I'd like override so I can add some conditional code. I've never override an ActiveRecord attribute before and wanted to know if the method below is good practice? class Article < ActiveRecord::Base def completed=(b) write_attribute(:completed, b) # IF b is true then do something end end

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  • In MS Access form, how to color background of selected record?

    - by PowerUser
    I have a somewhat complicated looking Access Form with a continuous display (meaning multiple records are shown at once). I'd like to change the background color of the selected record only so the end-user can easily tell which record they are on. I'm thinking of perhaps a conditional format or maybe something like this: Private Sub Detail_HasFocus() Detail.BackColor(me.color)=vbBlue End Sub and something similar for when that row loses focus. This code snippet obviously won't work, but it's the kind of code I'd like to achieve.

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  • Looking for Programming Language that allows you to change true and false.

    - by Maushu
    For my curiosity sake I'm looking for a dynamic object oriented language that allows you to change true to false and vice versa. Something like this: true = false, false = true; This should also affect any conditional statements, therefore 42 == 42 should return False. Basically, with this premise, nothing in the language would be safe from the programmer. Is there any language like this?

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  • How should I write this string-prefix check so that it's idiomatic Python?

    - by Kevin Stargel
    I have a couple of lists of items: specials = ['apple', 'banana', 'cherry', ...] smoothies = ['banana-apple', 'mocha mango', ...] I want to make a new list, special_smoothies, consisting of elements in smoothies that start with the elements in specials. However, if specials is blank, special_smoothies should be identical to smoothies. What's the most Pythonic way to do this? Is there a way to do this without a separate conditional check on whether specials is blank?

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  • How to handle failure to release a resource which is contained in a smart pointer?

    - by cj
    How should an error during resource deallocation be handled, when the object representing the resource is contained in a shared pointer? Smart pointers are a useful tool to manage resources safely. Examples of such resources are memory, disk files, database connections, or network connections. // open a connection to the local HTTP port boost::shared_ptr<Socket> socket = Socket::connect("localhost:80"); In a typical scenario, the class encapsulating the resource should be noncopyable and polymorphic. A good way to support this is to provide a factory method returning a shared pointer, and declare all constructors non-public. The shared pointers can now be copied from and assigned to freely. The object is automatically destroyed when no reference to it remains, and the destructor then releases the resource. /** A TCP/IP connection. */ class Socket { public: static boost::shared_ptr<Socket> connect(const std::string& address); virtual ~Socket(); protected: Socket(const std::string& address); private: // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; But there is a problem with this approach. The destructor must not throw, so a failure to release the resource will remain undetected. A common way out of this problem is to add a public method to release the resource. class Socket { public: virtual void close(); // may throw // ... }; Unfortunately, this approach introduces another problem: Our objects may now contain resources which have already been released. This complicates the implementation of the resource class. Even worse, it makes it possible for clients of the class to use it incorrectly. The following example may seem far-fetched, but it is a common pitfall in multi-threaded code. socket->close(); // ... size_t nread = socket->read(&buffer[0], buffer.size()); // wrong use! Either we ensure that the resource is not released before the object is destroyed, thereby losing any way to deal with a failed resource deallocation. Or we provide a way to release the resource explicitly during the object's lifetime, thereby making it possible to use the resource class incorrectly. There is a way out of this dilemma. But the solution involves using a modified shared pointer class. These modifications are likely to be controversial. Typical shared pointer implementations, such as boost::shared_ptr, require that no exception be thrown when their object's destructor is called. Generally, no destructor should ever throw, so this is a reasonable requirement. These implementations also allow a custom deleter function to be specified, which is called in lieu of the destructor when no reference to the object remains. The no-throw requirement is extended to this custom deleter function. The rationale for this requirement is clear: The shared pointer's destructor must not throw. If the deleter function does not throw, nor will the shared pointer's destructor. However, the same holds for other member functions of the shared pointer which lead to resource deallocation, e.g. reset(): If resource deallocation fails, no exception can be thrown. The solution proposed here is to allow custom deleter functions to throw. This means that the modified shared pointer's destructor must catch exceptions thrown by the deleter function. On the other hand, member functions other than the destructor, e.g. reset(), shall not catch exceptions of the deleter function (and their implementation becomes somewhat more complicated). Here is the original example, using a throwing deleter function: /** A TCP/IP connection. */ class Socket { public: static SharedPtr<Socket> connect(const std::string& address); protected: Socket(const std::string& address); virtual Socket() { } private: struct Deleter; // not implemented Socket(const Socket&); Socket& operator=(const Socket&); }; struct Socket::Deleter { void operator()(Socket* socket) { // Close the connection. If an error occurs, delete the socket // and throw an exception. delete socket; } }; SharedPtr<Socket> Socket::connect(const std::string& address) { return SharedPtr<Socket>(new Socket(address), Deleter()); } We can now use reset() to free the resource explicitly. If there is still a reference to the resource in another thread or another part of the program, calling reset() will only decrement the reference count. If this is the last reference to the resource, the resource is released. If resource deallocation fails, an exception is thrown. SharedPtr<Socket> socket = Socket::connect("localhost:80"); // ... socket.reset();

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  • "Use of uninitialised value" despite of memset

    - by Framester
    Hi there, I allocate a 2d array and use memset to fill it with zeros. #include<stdio.h> #include<string.h> #include<stdlib.h> void main() { int m=10; int n =10; int **array_2d; array_2d = (int**) malloc(m*sizeof(int*)); if(array_2d==NULL) { printf("\n Could not malloc 2d array \n"); exit(1); } for(int i=0;i<m;i++) { ((array_2d)[i])=malloc(n*sizeof(int)); memset(((array_2d)[i]),0,sizeof(n*sizeof(int))); } for(int i=0; i<10;i++){ for(int j=0; j<10;j++){ printf("(%i,%i)=",i,j); fflush(stdout); printf("%i ", array_2d[i][j]); } printf("\n"); } } Afterwards I use valgrind [1] to check for memory errors. I get following error: Conditional jump or move depends on uninitialised value(s) for line 24 (printf("%i ", array_2d[i][j]);). I always thought memset is the function to initialize arrays. How can I get rid off this error? Thanks! Valgrind output: ==3485== Memcheck, a memory error detector ==3485== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al. ==3485== Using Valgrind-3.5.0-Debian and LibVEX; rerun with -h for copyright info ==3485== Command: ./a.out ==3485== (0,0)=0 (0,1)===3485== Use of uninitialised value of size 4 ==3485== at 0x409E186: _itoa_word (_itoa.c:195) ==3485== by 0x40A1AD1: vfprintf (vfprintf.c:1613) ==3485== by 0x40A8FFF: printf (printf.c:35) ==3485== by 0x8048724: main (playing_with_valgrind.c:39) ==3485== ==3485== ==3485== ---- Attach to debugger ? --- [Return/N/n/Y/y/C/c] ---- ==3485== Conditional jump or move depends on uninitialised value(s) ==3485== at 0x409E18E: _itoa_word (_itoa.c:195) ==3485== by 0x40A1AD1: vfprintf (vfprintf.c:1613) ==3485== by 0x40A8FFF: printf (printf.c:35) ==3485== by 0x8048724: main (playing_with_valgrind.c:39) [1] valgrind --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes --db-attach=yes ./a.out [gcc-cmd] gcc -std=c99 -lm -Wall -g3 playing_with_valgrind.c

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  • Drupal - special css file if JS is turned off?

    - by jsims281
    I'm building a Drupal theme up and want to know if there is a Drupalish way to add a css file only if the user has js turned off. This would ideally go in the theme.info file to keep it neat! Something like this would be ideal: conditional-stylesheets[if no javascript][all][] = nojs.css If this isn't possible then I'm going to keep all the css that needs JS out of the css files, and add it dynamically using JS but this seems a bit messy... Any ideas?

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  • why is optional chaining required in an if let statement

    - by b-ryan ca
    Why would the Swift compiler expect me to write if let addressNumber = paul.residence?.address?.buildingNumber?.toInt() { } instead of just writing: if let addressNumber = paul.residence.address.buildingNumber.toInt() { } The compiler clearly has the static type information to handle the conditional statement for the first dereference of the optional value and each following value. Why would it not continue to do so for the following statements?

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  • SSIS Null Value Questions

    - by Saobi
    I have a table with 5 string columns, all can be NULLs. After I read the data from this table, I want to convert any null values into empty strings. The reason is that I need to compare these columns with columns in another table of the same schema (using conditional split), and null values would cause the comparison to evaluate to NULL. Is there any functionality in SSIS that allows me to convert NULL's to empty strings, or just not having to deal with NULL's at all?

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  • Detecting jQuery UI autocomplete

    - by Soldarnal
    How can I detect whether or not an input box is currently a jQuery UI autocomplete? There doesn't seem to be a native method for this, but I'm hoping there is something simple like this: if ($("#q").autocomplete) { //Do something } That conditional, however, seems to always return true.

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  • MySql - set of time stamped data (timestamp,event) calculating events per day

    - by Kevin Ohashi
    I have a table: id, datetime, event i also have table dates: date (Y-m-d format) the problem is some days don't have any events, I would like them to show 0 (or null) SELECT DATE_FORMAT(table.timestamp, '%Y-%m-%d') ydm, count(table.fkUID) FROM `table` where table.fkUID=$var group by ydm; is there some way to join or use conditional statements to make the result show: date|count ---------- 2010-05-23| 5 2010-05-24| 0 <--- this line just doesn't exist in my query. 2010-05-26| 3

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  • htaccess redirect to www excluding subdomains both https and http

    - by wes
    So this is what I currently have, I'm trying to redirect http://something.com to http://www.something.com but if its a subdomain do no such things, so http://other.somethings.com will stay the same AND conditional based on https/http Currently have.. RewriteCond %{HTTP_HOST} !^www. RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

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  • OpenSSL 1.0: Remove Elliptic Curves Extension

    - by rursw1
    Hi, Is there any way to remove the elliptic curves extension - elliptic_curves and ec_point_formats? (Via function like SSL_CTX_set_options with SSL_OP_NO_TICKET for the SessionTicket extension, or by conditional compilation, or something else that works...) Thank you in advance!

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  • Does this language feature already exist?

    - by Pindatjuh
    I'm currently developing a new language for programming in a continuous environment (compare it to electrical engineering), and I've got some ideas on a certain language construction. Let me explain the feature by explanation and then by definition: x = a U b; Where x is a variable and a and b are other variables (or static values). This works like a union between a and b; no duplicates and no specific order. with(x) { // regular 'with' usage; using the global interpretation of "x" x = 5; // will replace the original definition of "x = a U b;" } with(x = a) { // this code block is executed when the "x" variable // has the "a" variable assigned. All references in // this code-block to "x" are references to "a". So saying: x = 5; // would only change the variable "a". If the variable "a" // later on changes, x still equals to 5, in this fashion: // 'x = a U b U 5;' // '[currentscope] = 5;' // thus, 'a = 5;' } with(x = b) { // same but with "b" } with(x != a) { // here the "x" variable refers to any variable // but "a"; thus saying x = 5; // is equal to the rewriting of // 'x = a U b U 5;' // 'b = 5;' (since it was the scope of this block) } with(x = (a U b)) { // guaranteed that "x" is 'a U b'; interacting with "x" // will interact with both "a" and "b". x = 5; // makes both "a" and "b" equal to 5; also the "x" variable // is updated to contain: // 'x = a U b U 5;' // '[currentscope] = 5;' // 'a U b = 5;' // and thus: 'a = 5; b = 5;'. } // etc. In the above, all code-blocks are executed, but the "scope" changes in each block how x is interpreted. In the first block, x is guaranteed to be a: thus interacting with x inside that block will interact on a. The second and the third code-block are only equal in this situation (because not a: then there only remains b). The last block guarantees that x is at least a or b. Further more; U is not the "bitwise or operator", but I've called it the "and/or"-operator. Its definition is: "U" = "and" U "or" (On my blog, http://cplang.wordpress.com/2009/12/19/binop-and-or/, there is more (mathematical) background information on this operator. It's loosely based on sets. Using different syntax, changed it in this question.) Update: more examples. print = "Hello world!" U "How are you?"; // this will print // both values, but the // order doesn't matter. // 'userkey' is a variable containing a key. with(userkey = "a") { print = userkey; // will only print "a". } with(userkey = ("shift" U "a")) { // pressed both "shift" and the "a" key. print = userkey; // will "print" shift and "a", even // if the user also pressed "ctrl": // the interpretation of "userkey" is changed, // such that it only contains the matched cases. } with((userkey = "shift") U (userkey = "a")) { // same as if-statement above this one, showing the distributivity. } x = 5 U 6 U 7; y = x + x; // will be: // y = (5 U 6 U 7) + (5 U 6 U 7) // = 10 U 11 U 12 U 13 U 14 somewantedkey = "ctrl" U "alt" U "space" with(userkey = somewantedkey) { // must match all elements of "somewantedkey" // (distributed the Boolean equals operated) // thus only executed when all the defined keys are pressed } with(somewantedkey = userkey) { // matches only one of the provided "somewantedkey" // thus when only "space" is pressed, this block is executed. } Update2: more examples and some more context. with(x = (a U b)) { // this } // can be written as with((x = a) U (x = b)) { // this: changing the variable like x = 5; // will be rewritten as: // a = 5 and b = 5 } Some background information: I'm building a language which is "time-independent", like Java is "platform-independant". Everything stated in the language is "as is", and is continuously actively executed. This means; the programmer does not know in which order (unless explicitly stated using constructions) elements are, nor when statements are executed. The language is completely separated from the "time"-concept, i.e. it's continuously executed: with(a < 5) { a++; } // this is a loop-structure; // how and when it's executed isn't known however. with(a) { // everytime the "a" variable changes, this code-block is executed. b = 4; with(b < 3) { // runs only three times. } with(b > 0) { b = b - 1; // runs four times } } Update 3: After pondering on the type of this language feature; it closely resemblances Netbeans Platform's Lookup, where each "with"-statement a synchronized agent is, working on it's specific "filter" of objects. Instead of type-based, this is variable-based (fundamentally quite the same; just a different way of identifiying objects). I greatly thank all of you for providing me with very insightful information and links/hints to great topics I can research. Thanks. I do not know if this construction already exists, so that's my question: does this language feature already exist?

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