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  • Is there a language with native pass-by-reference/pass-by-name semantics, which could be used in mod

    - by Bubba88
    Hi! This is a reopened question. I look for a language and supporting platform for it, where the language could have pass-by-reference or pass-by-name semantics by default. I know the history a little, that there were Algol, Fortran and there still is C++ which could make it possible; but, basically, what I look for is something more modern and where the mentioned value pass methodology is preferred and by default (implicitly assumed). I ask this question, because, to my mind, some of the advantages of pass-by-ref/name seem kind of obvious. For example when it is used in a standalone agent, where copyiong of values is not necessary (to some extent) and performance wouldn't be downgraded much in that case. So, I could employ it in e.g. rich client app or some game-style or standalone service-kind application. The main advantage to me is the clear separation between identity of a symbol, and its current value. I mean when there is no reduntant copying, you know that you're working with the exact symbol/path you have queried/received. And intristing boxing of values will not interfere with the actual logic of program. I know that there is C# ref keyword, but it's something not so intristic, though acceptable. Equally, I realize that pass-by-reference semantics could be simulated in virtually any language (Java as an instant example) and so on.. not sure about pass by name :) What would you recommend - create a something like DSL for such needs wherever it be appropriate; or use some languages that I already know? Maybe, there is something that I'm missing? Thank you!

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  • Reference remotely located assembly (web uri) from locally installed application?

    - by moonground.de
    Hi Stackoverflowers! :) We have a .NET application for Windows which is installed locally by Microsoft Installer. Now we have the need to use additional assemblies which are located online at our Web Servers. We'd like to refer to a remote uri like https://www.ourserver.com/OurProductName/ExternalLib.dll and reveal additional functionality, which is described roughly by a known common ("AddIn/Plugin") Interface. These are not 3rd Party Plugins, we just want be able to exchange parts of the application frequently, without the need to have frequent software updates. Our first idea was to add some kind of "remote refence" in Visual Studio by setting the path to the remote assembly uri. But Visual Studio downloaded the assembly immediately to a temporary directory, adding a reference to it. Our second attempt then, is simply using a WebRequest (or WebClient) to retrieve a binary stream of the Assembly, loading it "from image" by using Assembly.Load(...). This actually works, but is not very elegant and requires more additional programming for verification etc. We hoped Clickonce would provide useful techniques but apparently it's suitable for standalone applications only. (Correct me?) Is there a way (.net native or by framework/api) to reference remotely located assemblies? Thanks in advance and have a happy easter!

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  • How can I pass an array resulting from a Perl method by reference?

    - by arareko
    Some XML::LibXML methods return arrays instead of references to arrays. Instead of doing this: $self->process_items($xml->findnodes('items/item')); I want to do something like: $self->process_items(\$xml->findnodes('items/item')); So that in process_items() I can dereference the original array instead of creating a copy: sub process_items { my ($self, $items) = @_; foreach my $item (@$items) { # do something... } } I can always store the results of findnodes() into an array and then pass the array reference to my own method, but let's say I want to try a reduced version of my code. Is that the correct syntax for passing the method results or should I use something different? Thanks! EDIT: Now suppose I want to change process_items() to process_item() so I can do stuff on a single element of the referenced array inside a loop. Something like: $self->process_item($_) for ([ $xml->findnodes('items/item') ]); This doesn't work as process_item() is executed only once because a single value is passed to the for loop (the reference to the array from findnodes()). What's the proper way of using $_ in this case?

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  • Is method reference caching a good idea in Java 8?

    - by gexicide
    Consider I have code like the following: class Foo { Y func(X x) {...} void doSomethingWithAFunc(Function<X,Y> f){...} void hotFunction(){ doSomethingWithAFunc(this::func); } } Consider that hotFunction is called very often. Would it then be advisable to cache this::func, maybe like this: class Foo { Function<X,Y> f = this::func; ... void hotFunction(){ doSomethingWithAFunc(f); } } As far as my understanding of java method references goes, the Virtual Machine creates an object of an anonymous class when a method reference is used. Thus, caching the reference would create that object only once while the first approach creates it on each function call. Is this correct? Should method references that appear at hot positions in the code be cached or is the VM able to optimize this and make the caching superfluous? Is there a general best practice about this or is this highly VM-implemenation specific whether such caching is of any use?

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  • Friendly way to override `const`-overloaded member function?

    - by xtofl
    Given a base class class A { int i; public: int& f(){ return i;} const int& f() const { return i;} }; And a sub class class ConstA : private A { public: const int& f() const { return A::f(); } }; Is there a wrist-friendly way to access the ConstA::f method on a non-const variable? ConstA ca; int i = ca.f(); // compile error: int& A::f() is not accessible since A is privately inherited int j = static_cast<const ConstA&>(ca).f(); // this works, but it hurts a little... Or is it so ugly since hiding A::f generally is a bad idea, violating the Liskov Substitution Principle: any subclass of A must at least be capable of all A's functionality? void set( A& a, int i ) { a.f() = i; } class ConstA2 : public A { private: int& f(){ return A::f(); } }; ConstA2 ca2; set( ca2, 1 ); (Note: this question popped up while thinking about this question)

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  • Avoiding That Null Reference!

    - by TheJuice
    A coworker had this conversation with another of our developers. Names have been changed to protect the guilty. Clueless: hey! Clueless: I am using the ?? operator for null check below Nice Guy: hey Clueless: FundLoanRequestBoatCollateral boatCollateral = request.BoatCollateral ?? null; Nice Guy: that's not exactly how it works Clueless: I want to achive: FundLoanRequestBoatCollateral boatCollateral = request.BoatCollateral != null ? request.BoatCollateral : null; Clueless: isnt that equal to:  FundLoanRequestBoatCollateral boatCollateral = request.BoatCollateral ?? null; Nice Guy: that is functionally equivalent to FundLoanRequestBoatCollateral boatCollateral = request.BoatCollateral Nice Guy: you're checking if it's null and if so setting it to null Clueless: yeah Clueless: if its null I want to set it to null Nice Guy: if it's null then you're already going to set it to null, no special logic needed Clueless: I wanted to avoid a null reference if BoatCollateral is null   The sad part of all of this is that "Clueless" has been with our company for years and has a Master's in Computer Science.

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  • Add Reference with Search

    - by Daniel Cazzulino
    If you have been using VS2010 for any significant amount of time, you surely came across the awkward, slow and hard to use Add Reference dialog. Despite some (apparent) improvements over the VS2008 behavior, in its current form it's even LESS usable than before. A brief non-exhaustive summary of the typical grief with this dialog is: Scrolling a list of *hundreds* of entries? (300+ typically) No partial matching when typing: yes, you can type in the list to get to the desired entry, but the matching is performed in an exact manner, from the beginning of the assembly name. So, to get to the (say) "Microsoft.VisualStudio.Settings" assembly, you actually have to type the first two segments in their entirety before starting to type "Settings"....Read full article

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  • Comparing the Performance of Visual Studio&apos;s Web Reference to a Custom Class

    As developers, we all make assumptions when programming. Perhaps the biggest assumption we make is that those libraries and tools that ship with the .NET Framework are the best way to accomplish a given task. For example, most developers assume that using <a href="http://www.4guysfromrolla.com/articles/120705-1.aspx">ASP.NET's Membership system</a> is the best way to manage user accounts in a website (rather than rolling your own user account store). Similarly, creating a Web Reference to communicate with a <a href="http://www.4guysfromrolla.com/articles/100803-1.aspx">web service</a> generates markup that auto-creates a <i>proxy class</i>, which handles the low-level details of invoking the web service, serializing parameters,

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  • Strange problem with libc: undefined reference to `crypt'

    - by sorush-r
    I moved from Archlinux to Kubuntu 12.04 yesterday. I compiled buildroot 2012.08 on Archlinux without any problem. Though on Kubuntu libcrypt seems to be broken. sysvinit can't find it anywhere. glibc-dev and all dependencies are installed. How do I link to libcrypt? Or, which package containts that library? ... bc-gcc sulogin.o -o sulogin sulogin.o: In function `main': sulogin.c:(.text+0x49d): undefined reference to `crypt' collect2: ld returned 1 exit status

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  • Generic Handler vs Direct Reference

    - by JNF
    In a project where I'm working on the data access layer I'm trying to make a decision how to send data and objects to the next layer (and programmer). Is it better to tell him to reference my dll, OR should I build a generic handler and let him take the objects from there (i.e. json format) If I understand correctly, In case of 2. he would have to handle the objects on his own, whereas in case 1. he will have the entities I've built. Note: It is very probable that other people would need to take the same data, though, we're not up to that yet. Same question here - should I make it into a webservice, or have them access the handler?

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  • C++0x Overload on reference, versus sole pass-by-value + std::move?

    - by dean
    It seems the main advice concerning C++0x's rvalues is to add move constructors and move operators to your classes, until compilers default-implement them. But waiting is a losing strategy if you use VC10, because automatic generation probably won't be here until VC10 SP1, or in worst case, VC11. Likely, the wait for this will be measured in years. Here lies my problem. Writing all this duplicate code is not fun. And it's unpleasant to look at. But this is a burden well received, for those classes deemed slow. Not so for the hundreds, if not thousands, of smaller classes. ::sighs:: C++0x was supposed to let me write less code, not more! And then I had a thought. Shared by many, I would guess. Why not just pass everything by value? Won't std::move + copy elision make this nearly optimal? Example 1 - Typical Pre-0x constructor OurClass::OurClass(const SomeClass& obj) : obj(obj) {} SomeClass o; OurClass(o); // single copy OurClass(std::move(o)); // single copy OurClass(SomeClass()); // single copy Cons: A wasted copy for rvalues. Example 2 - Recommended C++0x? OurClass::OurClass(const SomeClass& obj) : obj(obj) {} OurClass::OurClass(SomeClass&& obj) : obj(std::move(obj)) {} SomeClass o; OurClass(o); // single copy OurClass(std::move(o)); // zero copies, one move OurClass(SomeClass()); // zero copies, one move Pros: Presumably the fastest. Cons: Lots of code! Example 3 - Pass-by-value + std::move OurClass::OurClass(SomeClass obj) : obj(std::move(obj)) {} SomeClass o; OurClass(o); // single copy, one move OurClass(std::move(o)); // zero copies, two moves OurClass(SomeClass()); // zero copies, one move Pros: No additional code. Cons: A wasted move in cases 1 & 2. Performance will suffer greatly if SomeClass has no move constructor. What do you think? Is this correct? Is the incurred move a generally acceptable loss when compared to the benefit of code reduction?

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  • template pass by const reference

    - by 7vies
    Hi, I've looked over a few similar questions, but I'm still confused. I'm trying to figure out how to explicitly (not by compiler optimization etc) and C++03-compatible avoid copying of an object when passing it to a template function. Here is my test code: #include <iostream> using namespace std; struct C { C() { cout << "C()" << endl; } C(const C&) { cout << "C(C)" << endl; } ~C() { cout << "~C()" << endl; } }; template<class T> void f(T) { cout << "f<T>" << endl; } template<> void f(C c) { cout << "f<C>" << endl; } // (1) template<> void f(const C& c) { cout << "f<C&>" << endl; } // (2) int main() { C c; f(c); return 0; } (1) accepts the object of type C, and makes a copy. Here is the output: C() C(C) f<C> ~C() ~C() So I've tried to specialize with a const C& parameter (2) to avoid this, but this simply doesn't work (apparently the reason is explained in this question). Well, I could "pass by pointer", but that's kind of ugly. So is there some trick that would allow to do that somehow nicely? EDIT: Oh, probably I wasn't clear. I already have a templated function template<class T> void f(T) {...} But now I want to specialize this function to accept a const& to another object: template<> void f(const SpecificObject&) {...} But it only gets called if I define it as template<> void f(SpecificObject) {...}

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  • C++: Retriving values of static const variables at a constructor of a static variable

    - by gilbertc
    I understand that the code below would result segmentation fault because at the cstr of A, B::SYMBOL was not initialized yet. But why? In reality, A is an object that serves as a map that maps the SYMBOLs of classes like B to their respective IDs. C holds this map(A) static-ly such that it can provide the mapping as a class function. The primary function of A is to serve as a map for C that initializes itself at startup. How should I be able to do that without segmentation fault, provided that I can still use B::ID and B::SYMBOL in the code (no #define pls)? Thanks! Gil. class A { public: A() { std::cout<<B::ID<<std::endl; std::cout<<B::SYMBOL<<std::endl; } }; class B { public: static const int ID; static const std::string SYMBOL; } const int B::ID = 1; const std::string B::SYMBOL = "B"; class C { public: static A s_A; }; A C::s_A; int main(int c, char** p) { }

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  • sizeof abuse : get the size of a const table

    - by shodanex
    When declaring a const table, it is possible to get the size of the table using sizeof. However, once you stop using the symbol name, it does not work anymore. is there a way to have the following program output the correct size for table A, instead of 0 ? #include <stdio.h> struct mystruct { int a; short b; }; const struct mystruct tableA[] ={ { .a = 1, .b = 2, }, { .a = 2, .b = 2, }, { .a = 3, .b = 2, }, }; const struct mystruct tableB[] ={ { .a = 1, .b = 2, }, { .a = 2, .b = 2, }, }; int main(int argc, char * argv[]) { int tbl_sz; const struct mystruct * table; table = tableA; tbl_sz = sizeof(table)/sizeof(struct mystruct); printf("size of table A : %d\n", tbl_sz); table = tableB; tbl_sz = sizeof(tableB)/sizeof(struct mystruct); printf("size of table B : %d\n", tbl_sz); return 0; } Output is : size of table A : 0 size of table B : 2

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  • Simplest way to automatically alter "const" value in Java during compile time

    - by Michael Mao
    Hi all: This is a question corresponds to my uni assignment so I am very sorry to say I cannot adopt any one of the following best practices in a short time -- you know -- assignment is due tomorrow :( link to Best way to alter const in Java on StackOverflow Basically the only task (I hope so) left for me is the performance tuning. I've got a bunch of predefined "const" values in my single-class agent source code like this: //static final values private static final long FT_THRESHOLD = 400; private static final long FT_THRESHOLD_MARGIN = 50; private static final long FT_SMOOTH_PRICE_IDICATOR = 20; private static final long FT_BUY_PRICE_MODIFIER = 0; private static final long FT_LAST_ROUNDS_STARTTIME = 90; private static final long FT_AMOUNT_ADJUST_MODIFIER = 5; private static final long FT_HISTORY_PIRCES_LENGTH = 10; private static final long FT_TRACK_DURATION = 5; private static final int MAX_BED_BID_NUM_PER_AUC = 12; I can definitely alter the values manually and then compile the code to give it another go around. But the execution time for a thorough "statistic analysis" usually requires over 2000 times of execution, which will typically lasts more than half an hour on my own laptop... So I hope there is a way to alter values using other ways than dig into the source code to change the "const" values there, so I can automatically distributed compiled code to other people's PC and let them run the statistic analysis instead. One other reason for a automatically value adjustment is that I can try using my own agent to defeat itself by choosing different "const" values. Although my values are derived from previous history and statistical results, they are far from the most optimized values. I hope there is a easy way so I can quickly adopt that so to have a good sleep tonight while the computer does everything for me... :) Any hints on this sort of stuff? Any suggestion is welcomed and much appreciated.

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  • why BOOST_FOREACH cannot handle const boost::ptr_map?

    - by psaghelyi
    void main() { typedef boost::ptr_map<int, char> MyMap; MyMap mymap; mymap[1] = 'a'; mymap[2] = 'b'; mymap[3] = 'c'; BOOST_FOREACH(MyMap::value_type value, mymap) { std::cout << value.first << " " << value.second << std::endl; } MyMap const & const_mymap = mymap; BOOST_FOREACH(MyMap::value_type value, const_mymap) { std::cout << value.first << " " << value.second << std::endl; } } The following error message comes from GCC at the second BOOST_FOREACH error: conversion from 'boost::ptr_container_detail::ref_pair<int, const char* const>' to non-scalar type 'boost::ptr_container_detail::ref_pair<int, char* const>' requested I reckon that this is the weakness of the pointer container's ref_pair...

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  • Source cross reference like LXR but written in PHP?

    - by Dan
    Hi, does someone know a good cross reference engine like LXR, but written in PHP? My provider has PHP and MySQL as well as Postgres DBs, but neither I have access to Perl nor via SSH. I'd like to put up a online cross ref for my Software which is written in C. Thanks for helping! Dan

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