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  • C++0x class factory with variadic templates problem

    - by randomenglishbloke
    I have a class factory where I'm using variadic templates for the c'tor parameters (code below). However, when I attempt to use it, I get compile errors; when I originally wrote it without parameters, it worked fine. Here is the class: template< class Base, typename KeyType, class... Args > class GenericFactory { public: GenericFactory(const GenericFactory&) = delete; GenericFactory &operator=(const GenericFactory&) = delete; typedef Base* (*FactFunType)(Args...); template <class Derived> static void Register(const KeyType &key, FactFunType fn) { FnList[key] = fn; } static Base* Create(const KeyType &key, Args... args) { auto iter = FnList.find(key); if (iter == FnList.end()) return 0; else return (iter->second)(args...); } static GenericFactory &Instance() { static GenericFactory gf; return gf; } private: GenericFactory() = default; typedef std::unordered_map<KeyType, FactFunType> FnMap; static FnMap FnList; }; template <class B, class D, typename KeyType, class... Args> class RegisterClass { public: RegisterClass(const KeyType &key) { GenericFactory<B, KeyType, Args...>::Instance().Register(key, FactFn); } static B *FactFn(Args... args) { return new D(args...); } }; Here is the error: when calling (e.g.) // Tucked out of the way RegisterClass<DataMap, PDColumnMap, int, void *> RC_CT_PD(0); GCC 4.5.0 gives me: In constructor 'RegisterClass<B, D, KeyType, Args>::RegisterClass(const KeyType&) [with B = DataMap, D = PDColumnMap, KeyType = int, Args = {void*}]': no matching function for call to 'GenericFactory<DataMap, int, void*>::Register(const int&, DataMap* (&)(void*))' I can't see why it won't compile and after extensive googling I couldn't find the answer. Can anyone tell me what I'm doing wrong (aside from the strange variable name, which makes sense in context)?

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  • Typedef in C# across several source files

    - by Danvil
    I am writing a C wrapper an would like to use a typedef aquivalent to define some types which should be valid in quite a lot of source files. Those "types" are just different aliases to [u]int16/32/64_t, but are useful to distinguish function parameters. One could use using MyId=System.Int32;, but this needs to be redeclared in every file as far as I see... Is there a better way?

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  • What happens in memory when calling a function with literal values?

    - by Drise
    Suppose I have an arbitrary function: void someFunc(int, double, char); and I call someFunc(8, 2.4, 'a');, what actually happens? How does 8, 2.4, and 'a' get memory, moved into that memory, and passed into the function? What type of optimizations does the compiler have for situations like these? What if I mix and match parameters, such like someFunc(myIntVar, 2.4, someChar);? What happens if the function is declared as inline?

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  • patterns in case statement in bash scripting

    - by Ramiro Rela
    The man says that case statements use "filename expansion pattern matching". I usually want to have short names for some parameters, so I go: case $1 in req|reqs|requirements) TASK="Functional Requirements";; met|meet|meetings) TASK="Meetings with the client";; esac logTimeSpentIn "$TASK" I tried patterns like "req*" or "me{e,}t" which I understand would expand correctly to match those values in the context of filename expansion, but it doesn't work. Thanks.

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  • .NET Results Class

    - by pm_2
    I have a C# function that does some processing and needs to return figures about what it has processed, success, failure, etc. Can anyone tell me if there are any standard framework classes that will handle this (for example, number of records processed, number successful, failed, etc) ? Alternatively, can anyone say how they usually handle this? Is the best way to create a class, or to use out parameters?

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  • How do I use multiple precisions in printf()?

    - by Tommy
    Looking at the information under the heading "Precision can be omitted or be any of:". The example: printf("%.*s", 3, "abcdef"); works, outputting:abc (truncating the rest of the string.) Now, I would like to have a string with multiple parameters formatted (truncated): printf("%.*s, %.*s", 3, 3, "abcdef", "xyz123"); but the program crashes. What is the correct syntax? Thank You.

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  • Override `drop` for a custom sequence

    - by Bruno Reis
    In short: in Clojure, is there a way to redefine a function from the standard sequence API (which is not defined on any interface like ISeq, IndexedSeq, etc) on a custom sequence type I wrote? 1. Huge data files I have big files in the following format: A long (8 bytes) containing the number n of entries n entries, each one being composed of 3 longs (ie, 24 bytes) 2. Custom sequence I want to have a sequence on these entries. Since I cannot usually hold all the data in memory at once, and I want fast sequential access on it, I wrote a class similar to the following: (deftype DataSeq [id ^long cnt ^long i cached-seq] clojure.lang.IndexedSeq (index [_] i) (count [_] (- cnt i)) (seq [this] this) (first [_] (first cached-seq)) (more [this] (if-let [s (next this)] s '())) (next [_] (if (not= (inc i) cnt) (if (next cached-seq) (DataSeq. id cnt (inc i) (next cached-seq)) (DataSeq. id cnt (inc i) (with-open [f (open-data-file id)] ; open a memory mapped byte array on the file ; seek to the exact position to begin reading ; decide on an optimal amount of data to read ; eagerly read and return that amount of data )))))) The main idea is to read ahead a bunch of entries in a list and then consume from that list. Whenever the cache is completely consumed, if there are remaining entries, they are read from the file in a new cache list. Simple as that. To create an instance of such a sequence, I use a very simple function like: (defn ^DataSeq load-data [id] (next (DataSeq. id (count-entries id) -1 []))) ; count-entries is a trivial "open file and read a long" memoized As you can see, the format of the data allowed me to implement count in very simply and efficiently. 3. drop could be O(1) In the same spirit, I'd like to reimplement drop. The format of these data files allows me to reimplement drop in O(1) (instead of the standard O(n)), as follows: if dropping less then the remaining cached items, just drop the same amount from the cache and done; if dropping more than cnt, then just return the empty list. otherwise, just figure out the position in the data file, jump right into that position, and read data from there. My difficulty is that drop is not implemented in the same way as count, first, seq, etc. The latter functions call a similarly named static method in RT which, in turn, calls my implementation above, while the former, drop, does not check if the instance of the sequence it is being called on provides a custom implementation. Obviously, I could provide a function named anything but drop that does exactly what I want, but that would force other people (including my future self) to remember to use it instead of drop every single time, which sucks. So, the question is: is it possible to override the default behaviour of drop? 4. A workaround (I dislike) While writing this question, I've just figured out a possible workaround: make the reading even lazier. The custom sequence would just keep an index and postpone the reading operation, that would happen only when first was called. The problem is that I'd need some mutable state: the first call to first would cause some data to be read into a cache, all the subsequent calls would return data from this cache. There would be a similar logic on next: if there's a cache, just next it; otherwise, don't bother populating it -- it will be done when first is called again. This would avoid unnecessary disk reads. However, this is still less than optimal -- it is still O(n), and it could easily be O(1). Anyways, I don't like this workaround, and my question is still open. Any thoughts? Thanks.

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  • nginx load balance with IIS backend servers waiting Host header

    - by Elgreco08
    i have a ubuntu 10.04 with nginx /0.8.54 running as a load balance proxy named: www.local.com I have two IIS backend servers which responds on Host header request web1.local.com web2.local.com Problem: When i hit my nginx balancer on www.local.com my backend servers respond with the default server blank webpage (IIS default page) since they are waiting for a right host header (e.g. web1.local.com) my nginx.conf upstream backend { server web1.local.com:80; server web2.local.com:80; } server { listen 80; location / { proxy_pass http://backend; proxy_set_header X-Real-IP $remote_addr; proxy_set_header Host $proxy_host; } } any hint ?

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  • php - clean URL

    - by tibin mathew
    Hai I want to create a web site with pure php. I want to hide the url parameters. I.e. I want to make my web site with clean urls. Is there is any way to do this with out using any framework? Is it curl help full to do this? Does any one give me a solution.

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  • How to project an ASP Classic Page?

    - by SH
    How to project an ASP Classic page with either HTTP AUTH (you must provide a username and password to OrderGroove) or a randomly generated access key that will be included as one of the parameters of the HTTP POST using the variable name access_key. Can anybody provide asp classic code in this regard? Quick help will be appreciated...

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  • do you call them functions, procedures or methods?

    - by lowlyintern
    consider a standard c# 'function' public void foo() { //some code } In c or c++ this is called a 'function' - even if taking no parameters and returning no value. In another language maybe it would be a 'procedure'. In object orientation speak it would be called a 'method' if a class member. What would be the correct term to use in c#?

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  • Reset disk does not work for different model of computer

    - by dato
    I've created a reset USB disk on my HP computer, with Windows 7 Ultimate 32-bit, and it works fine. However, it does not work for Acer computers (notebooks too), so what is the problem here? I've have created it for the same user named user, and the password is exactly the same as well. Is it possible to show the language bar with a keyboard shortcut at the logon screen in Windows 7? I know I can do it through Control Panel, but I can't log into the system. When I click Reset Passwword, it shows me my USB flash drive and says that the password hint is on this USB drive. Then I click Next and type the new passwword, then confirm this new password, but an error dialog is shown. It says that an error occured when trying to change the password for this user-

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  • Database web application

    - by Watergaite
    How would i go about creating a php application for my web page that can extract data from my database (i currently get the data in a CSV file). id also like the user to be able to filter the data by certain parameters. can u help

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  • Remove folder structure from archive, ignore folder while archiving and fix error

    - by Michael
    I am trying to make a script to backup each of my plesk hosts to individual files, I am having two problems: I would like to remove the folder structure from archive, the tar is 3 folders deep I am getting this error: tar: Removing leading `/' from member names I need my archive to ignore folders named "catch" because I don't need them in my archive. The code: FILES=/var/www/vhosts/* FNAME="" for f in $FILES do FNAME=`basename $f` tar cfv "/root/backup/ftp/$FNAME.tar" $f done Sample output: tar: Removing leading `/' from member names /var/www/vhosts/mydomain.com/ /var/www/vhosts/mydomain.com/conf /var/www/vhosts/mydomain.com/etc/ /var/www/vhosts/mydomain.com/etc/group /var/www/vhosts/mydomain.com/etc/termcap /var/www/vhosts/mydomain.com/etc/passwd /var/www/vhosts/mydomain.com/usr/

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  • View Lambdas in Visual Studio Debugger

    - by Vaccano
    I have the a simple LinqToSQL statement that is not working. Something Like this: List<MyClass> myList = _ctx.DBList .Where(x => x.AGuidID == paramID) .Where(x => x.BBoolVal == false) .ToList(); I look at _ctx.DBList in the debugger and the second item fits both parameters. Is there a way I can dig into this more to see what is going wrong?

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  • How does a frame retrieve the recipient's MAC address?

    - by Sarmen B.
    I am studying a Network+ book named All-in-one CompTia Network+ by Mike Meyers. In chapter 2 he talks about frames and how he represents them as canisters and the data within the frame contains the recipients mac address, senders mac address, data, and sequence number. What I don't understand is if the sender is sending a file via the network to the recipient, and this frame contains this data, how does the frame know what the recipients MAC address is before sending it? In regards to TCP/IP when it contains the recipients IP address, that's understandable how it retrieves that value. But I don't understand how it can retrieve the MAC address, because if that frame comes from the senders computer, goes into the router and copies itself to each and every computer that exists on the network, how did it have the MAC address to know where to go? Let me know if I'm not making sense.

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  • postfix + mysql, user unknown

    - by stoned
    I have installed postfix with dovecot and postfix admin and all seemed well at the beginning. I can log in with thunderbird and check the mailboxes (all empty now) and TRY to send mail, even TLS works. The problem comes when I try to send mail. This is the output of mail.log when I try to send mail from an address to the same address: Nov 23 16:41:55 mailforge postfix/local[6322]: 297792467C: to=, relay=local, delay=0.01, delays=0/0/0/0.01, dsn=5.1.1, status=bounced (unknown user: "test") Nov 23 16:41:55 mailforge postfix/qmgr[6293]: 297792467C: removed To me it looks like as if postfix tries to look for the user "test" while in the mysql database users are named as [email protected] . Where should I change this behaviour?

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  • question about function derivatives

    - by davit-datuashvili
    hi i have question for example i have some function int sumefunction(//parameters here let say int x){ return something let say x*x+2*x+3 or does not matter } i am interesting how find derivative of this function ?if i have int f(int x){ return sin(x); } after derivative it must return cos(x) thanks

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  • Overloading with same parameter signature

    - by Soham
    In C#, is it possible to have same parameters yet override each other(they are different in the return types) public override Stocks[] Search(string Field,string Param){ //some code} public override Stocks Search(string Field, string Param){//some code} C# returns compilation error

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  • call_user_function_array() and __construct

    - by John
    I'm working on a simple framework, and I'm having a slight problem. I'd like to use call_user_function_array() to pass parameters to a function. That's fine, except the function I want to pass it to is __construct. I can't create an instance of an object with cufa(), and by instantiating an object, and then using cufa to call that instance's __construct(), I run into problems with a broken class because I'm calling the constructor twice (and one time it's called wrong.)

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