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  • Why pass by const reference instead of by value?

    - by Maulrus
    From what I understand: when you pass by value, the function makes a local copy of the passed argument and uses that; when the function ends, it goes out of scope. When you pass by const reference, the function uses a reference to the passed argument that can't be modified. I don't understand, however, why one would choose one over the other, except in a situation where an argument needs to be modified and returned. If you had a void function where nothing is getting returned, why choose one over the other?

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  • How do you specify a 64 bit unsigned int const 0x8000000000000000 in VS2008?

    - by Mark Franjione
    I read about the Microsoft specific suffix "i64" for integer constants. I want to do an UNsigned shift to a ULONGLONG. ULONGLONG bigNum64 = 0x800000000000000i64 >> myval; In normal C, I would use the suffix "U", e.g. the similar 32 bit operation would be ULONG bigNum32 = 0x80000000U >> myval; I do NOT want the 2's complement sign extension to propogate through the high bits. I want an UNSIGNED shift on a 64 bit const number. I think my first statement is going to do a SIGNED shift right. I tried 0x800000000000000i64U and 0x800000000000000u64 but got compiler errors.

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  • shift reduce&& reduce reduce errors in build parser for python garmmer

    - by user366580
    i wanna build buttom up parser by java cup i write code in java cup , it is for python language so i used grammer was written in this site : but not all grammer , i choice partial set ,just while , identifer also i smiplified them when i did compile for the java cup that i write by write this command in command prompt window : java java_cup.Main -parser CalcParser -symbols CalcSymbol < javacupfile.cup i get conflict errors ,they are of type reduce-shift conflict and reduce-reduce conflict you can see to print screen of the errors in these links image 1 click here to see imge1 the grammer was in EBNF form in as refernce site and i convert it to BNF form maybe i make mistake in converting so i get such errors the origanl grammmer was // grammer in EBNF form identifier ::= (letter|"_") (letter | digit | "_")* letter ::= lowercase | uppercase lowercase ::= "a"..."z" uppercase ::= "A"..."Z" digit ::= "0"..."9 compound_stmt ::= if_stmt | while_stmt for_stmt ::= "for" target_list "in" expression_list ":" suite ["else" ":" suite] while_stmt ::= "while" expression ":" suite ["else" ":" suite] suite ::= stmt_list NEWLINE stmt_list ::= simple_stmt (";" simple_stmt)* [";"] simple_stmt ::= expression_stmt expression_stmt ::= expression_list expression_list ::= expression ( "," expression )* [","] expression ::= conditional_expression conditional_expression ::= or_test ["if" or_test "else" expression] or_test ::= and_test | or_test "or" and_test and_test ::= not_test | and_test "and" not_test not_test ::= comparison | "not" not_test comparison ::= or_expr ( comp_operator or_expr )* comp_operator ::= "<" | ">" | "==" | ">=" | "<=" | "<>" | "!=" | "is" ["not"] | ["not"] "in" or_expr ::= xor_expr | or_expr "|" xor_expr xor_expr ::= and_expr | xor_expr "^" and_expr and_expr ::= "&" | and_expr the grammer after converting to BNF form identifier ::=letterletter| letterdigit| letter"_"| "_"letter | "_"digit | "_""_" letter ::= lowercase | uppercase lowercase ::= "a"..."z" uppercase ::= "A"..."Z" digit ::= "0"..."9 while_stmt ::= "while" expression ":" suite "else" ":" suite |"while" expression ":" suite suite ::= stmt_list NEWLINE stmt_list ::= simple_stmt ";" simple_stmt stmt_list|";" simple_stmt ::= expression_stmt expression_stmt ::= expression_list expression_list ::= expression "," expression expression_list| "," expression ::= conditional_expression conditional_expression ::= or_test "if" or_test "else" expression |or_test or_test ::= and_test | or_test "or" and_test and_test ::= not_test | and_test "and" not_test not_test ::= comparison | "not" not_test comparison ::= or_expr comp_operator or_expr comp_operator ::= "<" | ">" | "==" | ">=" | "<=" | "<>" | "!=" | "is" ["not"] | ["not"] "in" or_expr ::= xor_expr | or_expr "|" xor_expr xor_expr ::= and_expr | xor_expr "^" and_expr and_expr ::= "&" | and_expr and the java cup file that i compile and get those errors is import java.io.*; terminal COMA; terminal ELSE; terminal WHILE; terminal NEWLINE; terminal SEMCOLON; terminal CAMMA; terminal IF; terminal OR; terminal AND; terminal NOT; terminal LESS; terminal GREATER; terminal EQUAL; terminal GREATERorE; terminal LESSorE; terminal NEQUAL; terminal OROP; terminal XOROP; terminal ANDOP; terminal Integer DIGIT; terminal java.lang.String LOWERCASE; terminal java.lang.String UPPERCASE; non terminal java.lang.String IDENTIFIER; non terminal java.lang.String LETTER; non terminal COMPOUND_STMT; non terminal WHILE_STMT; non terminal EXPRESSION; non terminal SUITE ; non terminal STMT_LIST; non terminal SIMPLE_STMT; non terminal EXPRESSION_STMT; non terminal EXPRESSION_LIST; non terminal CONDITITONAL_EXPRESSION; non terminal OR_TEST; non terminal AND_TEST; non terminal NOT_TEST; non terminal COMPARISON; non terminal COMP_OPERATOR; non terminal OR_EXPR; non terminal XOR_EXPR; non terminal AND_EXPR; IDENTIFIER ::=LETTER{: System.out.printf("lowercase"); :}| {: System.out.printf("uppercase"); :} LETTER{: System.out.printf("lowercase"); :}| {: System.out.printf("uppercase"); :}| LETTER{: System.out.printf("lowercase"); :}| {: System.out.printf("uppercase"); :} DIGIT; LETTER ::= LOWERCASE | UPPERCASE; COMPOUND_STMT ::=WHILE_STMT; WHILE_STMT ::= WHILE{: System.out.printf( "while"); :} EXPRESSION COMA {: System.out.printf(":"); :} SUITE ELSE {: System.out.printf("else" ); :} COMA{: System.out.printf( ":" ); :} SUITE |WHILE{: System.out.printf( "while" ); :} EXPRESSION COMA{: System.out.printf( ":" ); :} SUITE; SUITE ::= STMT_LIST NEWLINE{: System.out.printf( "newline" ); :}; STMT_LIST ::= SIMPLE_STMT SEMCOLON{: System.out.printf( ";" ); :} SIMPLE_STMT STMT_LIST|SEMCOLON{: System.out.printf( ";" ); :}; SIMPLE_STMT ::=EXPRESSION_STMT; EXPRESSION_STMT ::=EXPRESSION_LIST; EXPRESSION_LIST ::= EXPRESSION CAMMA{: System.out.printf( "," ); :} EXPRESSION EXPRESSION_LIST| CAMMA{: System.out.printf( "," ); :}; EXPRESSION ::= CONDITITONAL_EXPRESSION; CONDITITONAL_EXPRESSION ::= OR_TEST IF{: System.out.printf( "if"); :} OR_TEST ELSE{: System.out.printf("else"); :} EXPRESSION |OR_TEST; OR_TEST ::= AND_TEST | OR_TEST OR{: System.out.printf( "or"); :} AND_TEST; AND_TEST ::= NOT_TEST | AND_TEST AND{: System.out.printf( "and"); :} NOT_TEST; NOT_TEST ::= COMPARISON | NOT{: System.out.printf("not"); :} NOT_TEST; COMPARISON ::= OR_EXPR COMP_OPERATOR OR_EXPR ; COMP_OPERATOR ::= LESS{: System.out.printf( "<"); :} | GREATER{: System.out.printf(">"); :} | EQUAL{: System.out.printf("=="); :} | GREATERorE{: System.out.printf(">="); :} | LESSorE{: System.out.printf("<="); :} | NEQUAL{: System.out.printf("!="); :}; OR_EXPR ::= XOR_EXPR | OR_EXPR OROP{: System.out.printf("|"); :} XOR_EXPR; XOR_EXPR ::= AND_EXPR | XOR_EXPR XOROP {: System.out.printf("^"); :}XOR_EXPR; AND_EXPR ::= ANDOP{: System.out.printf("&"); :} | AND_EXPR; can any one told me how can solve this errors to build parser correcrtly??

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  • UAC prompt won't allow non-administrator to access IIS 7 Manager.

    - by Triynko
    The IIS 7 Manager seems to throw up a UAC prompt requiring administrative elevation as soon as the shortcut is clicked. This makes it impossible for a non-admin to use it. When I first created the user account, I could open IIS 7 Manager, but could not connect. I temporarily made the user account an Admin, then opened IIS 7 Manager again. Now that I've removed user from Admin, every time I open IIS 7 Manager it throws up the UAC prompt, making it impossible to do anything with it as a non-Admin. Is this a bug? Is there a way to reset the settings for this user so that IIS 7 Manager is back in some kind of first-run state?

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  • In what way does non-"full n-key rollover" hinder fast typists?

    - by Michael Kjörling
    Wikipedia claims (although the latter claim does not cite a source) that: High-end keyboards that provide full n-key rollover typically do so via a PS/2 interface as the USB mode most often used by operating systems has a maximum of only six keys plus modifiers that can be pressed at the same time.[4] This hinders fast typists, ... In what way would the system being able to recognize only six non-modifier keys at once hinder a fast typist? I consider myself a relatively fast typist and I usually press one key, plus modifiers, at once; I can't imagine any real-life situation in which the system only recognizing six non-modifier keys being pressed at once has been a limiting factor in my keyboard usage. (Multi-stroke keyboard shortcuts as used by high-end software like Visual Studio, Emacs and the like are a different matter.) Note that I am not really interested in answers centered around multiplayer computer games; I'm looking for answers that give reasons that would be relevant to typists, somehow supporting the statement made on Wikipedia.

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  • What to do if I get ping results for non-existing hosts?

    - by bublegumm
    When I am pinging non-existing host like 'zzz' or 'qwerty' I am getting the following result Pinging zzz.kanisa.com [209.62.20.200] with 32 bytes of data: Reply from 209.62.20.200: bytes=32 time=60ms TTL=46 Reply from 209.62.20.200: bytes=32 time=66ms TTL=46 It looks like a virus to me. But I was unable to find a solution on web. Any ideas how to fix it? Even more ridiculous results with nslookup C:\> nslookup google.com Server: google-public-dns-a.google.com Address: 8.8.8.8 Non-authoritative answer: Name: google.com.kanisa.com Address: 209.62.20.200 How to get rid of it?

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  • A Linux DHCP server that will listen on an non-broadcast (tap) interface?

    - by TomOnTime
    Are there any Linux DHCP servers that will listen to what Cisco calls an "unnumbered" interface, or what others might call a "NBMA" (non-broadcast) interface. I have a Linux system that connects to a number of others using GRE tunnels. The machines on the other end send DHCP requests to this machine, I can see them with tcpdump. However, ISC DHCP 3.0.3 refuses to listen to the interface because it is non-broadcast. The interface I'd like DHCP to listen to is: tap2 Link encap:Ethernet HWaddr removed-for-privacy inet6 addr: removed-for-privacy/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:518 errors:0 dropped:0 overruns:0 frame:0 TX packets:510 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:196242 (191.6 KiB) TX bytes:52425 (51.1 KiB)

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  • How do I make a privileged port non-privileged in Redhat 5?

    - by Jason Thompson
    So I have a RedHat 5 box that I'm wanting to run an application that I wrote that implements SLP. SLP uses port 427 for answering service queries. My understanding is that ports below 1024 are "privileged" and thus cannot be bound to by anyone that's not root. I cannot run this application as root as it is launched via tomcat. One creative solution I really like was simply writing an iptables rule to route the privileged port to a non-privileged. In my proof of concept tests, this works wonderfully. Unfortunately, it would be greatly (and understandably) desired by the powers if my application did not require screwing around with iptables upon installation. So I heard a rumor and cannot find anything to verify this that there was some sort of command or parameter that could be set to make any port I want be non-privileged. Is this true? If so, how is this done? Thanks!

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  • Pre-set OS X dock icon positions for non-permanent apps?

    - by Jack Sleight
    Is it possible to have OS X always place certain app icons in specific places (eg. position "two") in the dock, when they're not permanently docked apps? At the moment every non-permanent app is added to the end (far right), but, for example, if I have my mail and todo list apps open, I want them to pop up in positions one and two. I know this can easily be achieved by permanently docking icons, I'm specifically looking for a solution for non-permanent apps. I suspect OS X has no built in facility for this, perhaps there's a 3rd party app or script/command line trick?

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  • How can I launch a GUI session on a remote Ubuntu Desktop via SSH from a non-GUI Linux shell?

    - by Vihung
    I am setting up a test environment, made up of various Linux boxes, and I have the need to launch an instance of Firefox on a remote machine via ssh. The remote machine has Ubuntu Desktop (11) and Firefox installed. The source machine is a Continuous Integration server and it creates an ssh session to the remote machine from a non-GUI environment. It then runs a script, which tries to launch Firefox on the remote machine. However, since the ssh session is a from a non-GUI environment, there is no display. Is it possible to have a headless X-windows display? i.e. a virtual display in the remote environment for Firefox to run in? What options do I have?

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  • How can I make a non-destructive copy of a (NTFS) partition?

    - by violet313
    I want to recover some deleted files from a healthy NTFS partition on an undamaged hard-disk. In order to leave the partition undisturbed, i plan to use dd to clone the partition to a raw image file & then attempt recovery from that mounted clone. Will dd if=/dev/sd<xn> of=/path/to/output.img perform a non-destructive copy ? Is attempting a restore from a clone using dd the best approach? [edit, wrt Deltiks answer, i need to be a bit clearer about what i'm asking] eg: are there some s/w that can do something more with the original sectors ? eg: if it was a damaged hard-disk i am aware that any kind of read is potentially destructive. but assuming my disk head is not going to suddenly spaz out etc, am i reducing my chances of a successful recovery (at any cost) by using an apparently non-destructive single read of my undamaged hard-disk. (btw: i am planning on using ntfsundelete & testdisk for recovery)

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  • Asus ux31e zenbook SSD non-standard / cant upgrade hdd?

    - by FstaRocka
    I bought a ux31e asus zenbook, and the drive crashed last week. I just cancelled an mSata ssd order because I fear asus has used a non standard ssd!!! what a bunch of crooks, ive lost all my respect for this company! Can anyone confirm what and why? My SSD model is xm11 128gb - it looks like a ram chip and only has two tongues with 12 and 6 pins respectively. The drive I was about to order mSata had 8 where mine had 6 - i never bothered counting the rest. This article seems to confirm! UX31 UX21 Zenbook Article "It looks like SSD uses a non-standard format"

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  • Noob Objective-C/C++ - Linker Problem/Method Signature Problem

    - by Josh
    There is a static class Pipe, defined in C++ header that I'm including. The static method I'm interested in calling (from Objetive-c) is here: static ERC SendUserGet(const UserId &_idUser,const GUID &_idStyle,const ZoneId &_idZone,const char *_pszMsg); I have access to an objetive-c data structure that appears to store a copy of userID, and zoneID -- it looks like: @interface DataBlock : NSObject { GUID userID; GUID zoneID; } Looked up the GUID def, and its a struct with a bunch of overloaded operators for equality. UserId and ZoneId from the first function signature are #typedef GUID Now when I try to call the method, no matter how I cast it (const UserId), (UserId), etc, I get the following linker error: Ld build/Debug/Seeker.app/Contents/MacOS/Seeker normal i386 cd /Users/josh/Development/project/Mac/Seeker setenv MACOSX_DEPLOYMENT_TARGET 10.5 /Developer/usr/bin/g++-4.2 -arch i386 -isysroot /Developer/SDKs/MacOSX10.5.sdk -L/Users/josh/Development/TS/Mac/Seeker/build/Debug -L/Users/josh/Development/TS/Mac/Seeker/../../../debug -L/Developer/Platforms/iPhoneOS.platform/Developer/usr/lib/gcc/i686-apple-darwin10/4.2.1 -F/Users/josh/Development/TS/Mac/Seeker/build/Debug -filelist /Users/josh/Development/TS/Mac/Seeker/build/Seeker.build/Debug/Seeker.build/Objects-normal/i386/Seeker.LinkFileList -mmacosx-version-min=10.5 -framework Cocoa -framework WebKit -lSAPI -lSPL -o /Users/josh/Development/TS/Mac/Seeker/build/Debug/Seeker.app/Contents/MacOS/Seeker Undefined symbols: "SocPipe::SendUserGet(_GUID const&, _GUID const&, _GUID const&, char const*)", referenced from: -[PeoplePaneController clickGet:] in PeoplePaneController.o ld: symbol(s) not found collect2: ld returned 1 exit status Is this a type/function signature error, or truly some sort of linker error? I have the headers where all these types and static classes are defined #imported -- I tried #include too, just in case, since I'm already stumbling :P Forgive me, I come from a web tech background, so this c-style memory management and immutability stuff is super hazy. Edit: Added full linker error text. Changed "function" to "method" Thanks, Josh

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  • Noob Objective-C/C++ - Linker Problem/Function Def Problem

    - by Josh
    There is a static class Pipe, defined in C++ header that I'm including. The function I'm interested in calling (from Objetive-c) is here: static ERC SendUserGet(const UserId &_idUser,const GUID &_idStyle,const ZoneId &_idZone,const char *_pszMsg); I have access to an objetive-c data structure that appears to store a copy of userID, and zoneID -- it looks like: @interface DataBlock : NSObject { GUID userID; GUID zoneID; } Looked up the GUID def, and its a struct with a bunch of overloaded operators for equality. UserId and ZoneId from the first function signature are #typedef GUID Now when I try to call the function, no matter how I cast it (const UserId), (UserId), etc, I get the following linker error: "Pipe::SendUserGet(_GUID const&, _GUID const&, _GUID const&, char const*)", referenced from: -[PeoplePaneController clickGet:] in PeoplePaneController.o Is this a type/function signature error, or truly some sort of linker error? I have the headers where all these types and static classes are defined #imported -- I tried #include too, just in case, since I'm already stumbling :P Forgive me, I come from a web tech background, so this c-style memory management and immutability stuff is super hazy. Thanks, Josh

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  • Linking errors when building against Boost Unit Test Framework

    - by Rafid
    I am trying to use Boost Unit Test Framework by building a stand alone library as detailed here: http://www.boost.org/doc/libs/1_35_0/libs/test/doc/components/utf/compilation.html So I created a VC library project containing the mentioned files and build it and it was successful. Then I created a test project and referenced the library project I just created, but when I tried to build it, I got the following linking errors: 1>Type.obj : error LNK2019: unresolved external symbol "bool __cdecl boost::test_tools::tt_detail::check_impl(class boost::test_tools::predicate_result const &,class boost::unit_test::lazy_ostream const &,class boost::unit_test::basic_cstring<char const >,unsigned __int64,enum boost::test_tools::tt_detail::tool_level,enum boost::test_tools::tt_detail::check_type,unsigned __int64,...)" (?check_impl@tt_detail@test_tools@boost@@YA_NAEBVpredicate_result@23@AEBVlazy_ostream@unit_test@3@V?$basic_cstring@$$CBD@63@_KW4tool_level@123@W4check_type@123@3ZZ) referenced in function "public: void __cdecl test1::test_method(void)" (?test_method@test1@@QEAAXXZ) 1>BoostUnitTestFramework.lib(framework.obj) : error LNK2019: unresolved external symbol "void __cdecl boost::debug::break_memory_alloc(long)" (?break_memory_alloc@debug@boost@@YAXJ@Z) referenced in function "void __cdecl boost::unit_test::framework::init(class boost::unit_test::test_suite * (__cdecl*)(int,char * * const),int,char * * const)" (?init@framework@unit_test@boost@@YAXP6APEAVtest_suite@23@HQEAPEAD@ZH0@Z) 1>BoostUnitTestFramework.lib(framework.obj) : error LNK2019: unresolved external symbol "void __cdecl boost::debug::detect_memory_leaks(bool)" (?detect_memory_leaks@debug@boost@@YAX_N@Z) referenced in function "void __cdecl boost::unit_test::framework::init(class boost::unit_test::test_suite * (__cdecl*)(int,char * * const),int,char * * const)" (?init@framework@unit_test@boost@@YAXP6APEAVtest_suite@23@HQEAPEAD@ZH0@Z) 1>BoostUnitTestFramework.lib(execution_monitor.obj) : error LNK2019: unresolved external symbol "bool __cdecl boost::debug::attach_debugger(bool)" (?attach_debugger@debug@boost@@YA_N_N@Z) referenced in function "public: int __cdecl boost::detail::system_signal_exception::operator()(unsigned int,struct _EXCEPTION_POINTERS *)" (??Rsystem_signal_exception@detail@boost@@QEAAHIPEAU_EXCEPTION_POINTERS@@@Z) 1>BoostUnitTestFramework.lib(execution_monitor.obj) : error LNK2019: unresolved external symbol "bool __cdecl boost::debug::under_debugger(void)" (?under_debugger@debug@boost@@YA_NXZ) referenced in function "public: int __cdecl boost::execution_monitor::execute(class boost::unit_test::callback0<int> const &)" (?execute@execution_monitor@boost@@QEAAHAEBV?$callback0@H@unit_test@2@@Z) 1>BoostUnitTestFramework.lib(unit_test_main.obj) : error LNK2019: unresolved external symbol "class boost::unit_test::test_suite * __cdecl init_unit_test_suite(int,char * * const)" (?init_unit_test_suite@@YAPEAVtest_suite@unit_test@boost@@HQEAPEAD@Z) referenced in function main 1>C:\Users\Rafid\Workspace\MyPhysics\Builds\VC10\Tests\Debug\Tests.exe : fatal error LNK1120: 6 unresolved externals They seem to be mainly caused by Boost debug library, but I can't see a reason why I should get linking errors putting in mind that Boost debug library only need to be included as header files, rather than linking against as a library! Any ideas?!

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  • Storing class constants (for use as bitmask) in a database?

    - by fireeyedboy
    Let's say I have a class called Medium which can represent different types of media. For instance: uploaded video embedded video uploaded image embedded image I represent these types with contants, like this: class MediumAbstract { const UPLOAD = 0x0001; const EMBED = 0x0010; const VIDEO = 0x0100; const IMAGE = 0x1000; const VIDEO_UPLOAD = 0x0101; // for convenience const VIDEO_EMBED = 0x0110; // for convenience const IMAGE_UPLOAD = 0x1001; // for convenience const IMAGE_EMBED = 0x1010; // for convenience const ALL = 0x1111; // for convenience } Thus, it is easy for me to do a combined search on them on an (abstract) repository, with something like: { public function findAllByType( $type ) { ... } } $media = $repo->findAllByType( MediumAbstract::VIDEO | MediumAbstract::IMAGE_UPLOAD ); // or $media = $repo->findAllByType( MediumAbstract::ALL ); // etc.. How do you feel about using these constant values in a concrete repository like a database? Is it ok? Or should I substitute them with meaningful data in the database. Table medium: | id | type | location | etc.. ------------------------------------------------- | 1 | use constants here? | /some/path | etc.. (Of course I'll only be using the meaningful constants: VIDEO_UPLOAD, VIDEO_EMBED, IMAGE_UPLOAD and IMAGE_EMBED)

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  • Defining < for STL sort algorithm - operator overload, functor or standalone function?

    - by Andy
    I have a stl::list containing Widget class objects. They need to be sorted according to two members in the Widget class. For the sorting to work, I need to define a less-than comparator comparing two Widget objects. There seems to be a myriad of ways to do it. From what I can gather, one can either: a. Define a comparison operator overload in the class: bool Widget::operator< (const Widget &rhs) const b. Define a standalone function taking two Widgets: bool operator<(const Widget& lhs, const Widget& rhs); And then make the Widget class a friend of it: class Widget { // Various class definitions ... friend bool operator<(const Widget& lhs, const Widget& rhs); }; c. Define a functor and then include it as a parameter when calling the sort function: class Widget_Less : public binary_function<Widget, Widget, bool> { bool operator()(const Widget &lhs, const Widget& rhs) const; }; Does anybody know which method is better? In particular I am interested to know if I should do 1 or 2. I searched the book Effective STL by Scott Meyer but unfortunately it does not have anything to say about this. Thank you for your reply.

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  • Which cast am I using?

    - by Knowing me knowing you
    I'm trying to cast away const from an object but it doesn't work. But if I use old C-way of casting code compiles. So which casting I'm suppose to use to achieve this same effect? I wouldn't like to cast the old way. //file IntSet.h #include "stdafx.h" #pragma once /*Class representing set of integers*/ template<class T> class IntSet { private: T** myData_; std::size_t mySize_; std::size_t myIndex_; public: #pragma region ctor/dtor explicit IntSet(); virtual ~IntSet(); #pragma endregion #pragma region publicInterface IntSet makeUnion(const IntSet&)const; IntSet makeIntersection(const IntSet&)const; IntSet makeSymmetricDifference(const IntSet&)const; void insert(const T&); #pragma endregion }; //file IntSet_impl.h #include "StdAfx.h" #include "IntSet.h" #pragma region ctor/dtor template<class T> IntSet<T>::IntSet():myData_(nullptr), mySize_(0), myIndex_(0) { } IntSet<T>::~IntSet() { } #pragma endregion #pragma region publicInterface template<class T> void IntSet<T>::insert(const T& obj) { /*Check if we are initialized*/ if (mySize_ == 0) { mySize_ = 1; myData_ = new T*[mySize_]; } /*Check if we have place to insert obj in.*/ if (myIndex_ < mySize_) {//IS IT SAFE TO INCREMENT myIndex while assigning? myData_[myIndex_++] = &T(obj);//IF I DO IT THE OLD WAY IT WORKS return; } /*We didn't have enough place...*/ T** tmp = new T*[mySize_];//for copying old to temporary basket std::copy(&myData_[0],&myData_[mySize_],&tmp[0]); } #pragma endregion Thanks.

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  • Simple matrix example using C++ template class

    - by skyeagle
    I am trying to write a trivial Matrix class, using C++ templates in an attempt to brush up my C++, and also to explain something to a fellow coder. This is what I have som far: template class<T> class Matrix { public: Matrix(const unsigned int rows, const unsigned int cols); Matrix(const Matrix& m); Matrix& operator=(const Matrix& m); ~Matrix(); unsigned int getNumRows() const; unsigned int getNumCols() const; template <class T> T getCellValue(unsigned int row, unsigned col) const; template <class T> void setCellValue(unsigned int row, unsigned col, T value) const; private: // Note: intentionally NOT using smart pointers here ... T * m_values; }; template<class T> inline T Matrix::getCellValue(unsigned int row, unsigned col) const { } template<class T> inline void Matrix::setCellValue(unsigned int row, unsigned col, T value) { } I'm stuck on the ctor, since I need to allocate a new[] T, it seems like it needs to be a template method - however, I'm not sure I have come accross a templated ctor before. How can I implemnt the ctor?

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  • C++ Operator Ambiguity

    - by Scott
    Forgive me, for I am fairly new to C++, but I am having some trouble regarding operator ambiguity. I think it is compiler-specific, for the code compiled on my desktop. However, it fails to compile on my laptop. I think I know what's going wrong, but I don't see an elegant way around it. Please let me know if I am making an obvious mistake. Anyhow, here's what I'm trying to do: I have made my own vector class called Vector4 which looks something like this: class Vector4 { private: GLfloat vector[4]; ... } Then I have these operators, which are causing the problem: operator GLfloat* () { return vector; } operator const GLfloat* () const { return vector; } GLfloat& operator [] (const size_t i) { return vector[i]; } const GLfloat& operator [] (const size_t i) const { return vector[i]; } I have the conversion operator so that I can pass an instance of my Vector4 class to glVertex3fv, and I have subscripting for obvious reasons. However, calls that involve subscripting the Vector4 become ambiguous to the compiler: enum {x, y, z, w} Vector4 v(1.0, 2.0, 3.0, 4.0); glTranslatef(v[x], v[y], v[z]); Here are the candidates: candidate 1: const GLfloat& Vector4:: operator[](size_t) const candidate 2: operator[](const GLfloat*, int) <built-in> Why would it try to convert my Vector4 to a GLfloat* first when the subscript operator is already defined on Vector4? Is there a simple way around this that doesn't involve typecasting? Am I just making a silly mistake? Thanks for any help in advance.

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  • Failed to specialize function template

    - by citizencane
    This is homework, although it's already submitted with a different approach. I'm getting the following from Visual Studio 2008 error C2893: Failed to specialize function template 'void std::sort(_RanIt,_RanIt,_Pr)' The code is as follows main.cpp Database<> db; db.loadDatabase(); db.sortDatabase(sort_by_title()); Database.cpp void Database<C>::sortDatabase(const sort_by &s) { std::sort(db_.begin(), db_.end(), s); } And the function objects are defined as struct sort_by : public std::binary_function<const Media *, const Media *, bool> { virtual bool operator()(const Media *l, const Media *r) const = 0; }; struct sort_by_title : public sort_by { bool operator()(const Media *l, const Media *r) const { ... } }; ... What's the cure here? [Edit] Sorry, maybe I should have made the inheritance clear template <typename C = std::vector<Media *> > class Database : public IDatabase<C> [/Edit]

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  • How do I access abstract private data from derived class without friend or 'getter' functions in C++?

    - by John
    So, I am caught up in a dilemma right now. How am I suppose to access a pure abstract base class private member variable from a derived class? I have heard from a friend that it is possible to access it through the base constructor, but he didn't explain. How is it possible? There are some inherited classes from base class. Is there any way to gain access to the private variables ? class Base_button { private: bool is_vis; Rect rButton; public: // Constructors Base_button(); Base_button( const Point &corner, double height, double width ); // Destructor virtual ~ Base_button(); // Accessors virtual void draw() const = 0; bool clicked( const Point &click ) const; bool is_visible() const; // Mutators virtual void show(); virtual void hide(); void move( const Point &loc ); }; class Button : public Base_button { private: Message mButton; public: // Constructors Button(); Button( const Point &corner, const string &label ); // Acessors virtual void draw() const; // Mutators virtual void show(); virtual void hide(); }; I want to be able access Rect and bool in the base class from the subclass

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