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  • [C++] Multiple inheritance from template class

    - by Tom P.
    Hello, I'm having issues with multiple inheritance from different instantiations of the same template class. Specifically, I'm trying to do this: template <class T> class Base { public: Base() : obj(NULL) { } virtual ~Base() { if( obj != NULL ) delete obj; } template <class T> T* createBase() { obj = new T(); return obj; } protected: T* obj; }; class Something { // ... }; class SomethingElse { // ... }; class Derived : public Base<Something>, public Base<SomethingElse> { }; int main() { Derived* d = new Derived(); Something* smth1 = d->createBase<Something>(); SomethingElse* smth2 = d->createBase<SomethingElse>(); delete d; return 0; } When I try to compile the above code, I get the following errors: 1>[...](41) : error C2440: '=' : cannot convert from 'SomethingElse *' to 'Something *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast 1> [...](71) : see reference to function template instantiation 'T *Base<Something>::createBase<SomethingElse>(void)' being compiled 1> with 1> [ 1> T=SomethingElse 1> ] 1>[...](43) : error C2440: 'return' : cannot convert from 'Something *' to 'SomethingElse *' 1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast The issue seems to be ambiguity due to member obj being inherited from both Base< Something and Base< SomethingElse , and I can work around it by disambiguating my calls to createBase: Something* smth1 = d->Base<Something>::createBase<Something>(); SomethingElse* smth2 = d->Base<SomethingElse>::createBase<SomethingElse>(); However, this solution is dreadfully impractical, syntactically speaking, and I'd prefer something more elegant. Moreover, I'm puzzled by the first error message. It seems to imply that there is an instantiation createBase< SomethingElse in Base< Something , but how is that even possible? Any information or advice regarding this issue would be much appreciated.

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  • How to Detect Trusted Connection in Crystal Reports using VB.NET?

    - by Michael
    I have some Crystal Reports connecting to a Sql Server db that I would like to detect whether the connection is trusted or whether I need to supply the log on info (reports are not supplied by me so I can't control the connect method). If I just blindly supply login credentials, it won't connect if it is a trusted connection. The following does not work: oRpt = oCR.OpenReport("C:\MyReport.rpt") if oRpt.Database.Tables(1).ConnectionProperties.Item("Integrated Security") = True then 'trusted connection else 'supply login credentials end if It gives the following error: Operator '=' is not defined for type 'IConnectionProperty' and type 'Boolean'. I cannot find how create a construct in vb.net for IConnectionProperty. I can't find any documents from Crystal that explain it. I am using Crystal Reports XI - Developer

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  • What is the 'noreq' Filter Type an Alias for?

    - by Alan Storm
    I'm looking in to Magento's filtering options (Ecommerce System and PHP Framekwork with an expansive ORM system). Specifically the addFieldToFilter method. In this method, you specify a SQLish filter by passing in a single element array, with the key indicating the type of filter. For example, array('eq'=>'bar') //eq means equal array('neq'=>'bar') //neq means not equal would each give you a where clause that looks like where field = 'bar'; where field != 'bar'; So, deep in the bowels of the source, I found a comparison type named 'moreq' that maps to a = comparison operator array('moreq'=>'27') where field >= 27 The weird thing is, there's already a 'gteq' comparision type array('gteq'=>'27') where field >= 27 So, my question is, what does moreq stand for? Is is some special SQL concept that's supported in other databases that the Magento guys wants to map to MySQL, or is it just "more required" and an example what happens when you're doing rapid agile and trying to maintain backwards compatibility.

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  • Can items deleted from "Trash" be recovered?

    - by Miraaj
    Hi all, In mac we have option to delete items securely from trash, while deleting it warns that: once deleted items will not be recovered. I want to know that is there any way by which items deleted "normally, (not securely)" from "Trash" can be recovered? Thanks, Miraaj

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  • Filter objects within two seconds of one another using SQLAlchemy

    - by Arrieta
    Hello: I have two tables with a column 'date'. One holds (name, date) and the other holds (date, p1, p2). Given a name, I want to use the date in table 1 to query p1 and p2 from table two; the match should happen if date in table one is within two seconds of date in table two. How can you accomplish this using SQLAlchemy? I've tried (unsuccessfully) to use the between operator and with a clause like: td = datetime.timedelta(seconds=2) q = session.query(table1, table2).filter(table1.name=='my_name').\ filter(between(table1.date, table2.date - td, table2.date + td)) Any thoughts?

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  • Postgresql count+sort performance

    - by invictus
    I have built a small inventory system using postgresql and psycopg2. Everything works great, except, when I want to create aggregated summaries/reports of the content, I get really bad performance due to count()'ing and sorting. The DB schema is as follows: CREATE TABLE hosts ( id SERIAL PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE items ( id SERIAL PRIMARY KEY, description TEXT ); CREATE TABLE host_item ( id SERIAL PRIMARY KEY, host INTEGER REFERENCES hosts(id) ON DELETE CASCADE ON UPDATE CASCADE, item INTEGER REFERENCES items(id) ON DELETE CASCADE ON UPDATE CASCADE ); There are some other fields as well, but those are not relevant. I want to extract 2 different reports: - List of all hosts with the number of items per, ordered from highest to lowest count - List of all items with the number of hosts per, ordered from highest to lowest count I have used 2 queries for the purpose: Items with host count: SELECT i.id, i.description, COUNT(hi.id) AS count FROM items AS i LEFT JOIN host_item AS hi ON (i.id=hi.item) GROUP BY i.id ORDER BY count DESC LIMIT 10; Hosts with item count: SELECT h.id, h.name, COUNT(hi.id) AS count FROM hosts AS h LEFT JOIN host_item AS hi ON (h.id=hi.host) GROUP BY h.id ORDER BY count DESC LIMIT 10; Problem is: the queries runs for 5-6 seconds before returning any data. As this is a web based application, 6 seconds are just not acceptable. The database is heavily populated with approximately 50k hosts, 1000 items and 400 000 host/items relations, and will likely increase significantly when (or perhaps if) the application will be used. After playing around, I found that by removing the "ORDER BY count DESC" part, both queries would execute instantly without any delay whatsoever (less than 20ms to finish the queries). Is there any way I can optimize these queries so that I can get the result sorted without the delay? I was trying different indexes, but seeing as the count is computed it is possible to utilize an index for this. I have read that count()'ing in postgresql is slow, but its the sorting that are causing me problems... My current workaround is to run the queries above as an hourly job, putting the result into a new table with an index on the count column for quick lookup. I use Postgresql 9.2.

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  • C++ Segmentation fault in binary_function

    - by noryb009
    I'm using Visual Studio 2010 Beta 2 (also tried with NetBeans), and I'm having a segmentation fault in the following code: // One of the @link s20_3_3_comparisons comparison functors@endlink. template <class _Tp> struct less : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return __x < __y; } //this is the problem line }; I don't know what in my program calls it, but I am trying to find out. (I think it's a map) Does anyone know what to do, or has encountered this before?

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  • Dynamic allocated array is not freed

    - by Stefano
    I'm using the code above to dynamically allocate an array, do some work inside the function, return an element of the array and free the memory outside of the function. But when I try to deallocate the array it doesn't free the memory and I have a memory leak. The debugger pointed to the myArray variable shows me the error CXX0030. Why? struct MYSTRUCT { char *myvariable1; int myvariable2; char *myvariable2; .... }; void MyClass::MyFunction1() { MYSTRUCT *myArray= NULL; MYSTRUCT *myElement = this->MyFunction2(myArray); ... delete [] myArray; } MYSTRUCT* MyClass::MyFunction2(MYSTRUCT *array) { array = (MYSTRUCT*)operator new(bytesLength); ... return array[X]; }

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  • Possible to fire asp.net validation from jQuery?

    - by Abe Miessler
    I have a form with several text boxes on it. I only want to accept floats, but it is likely that users will enter a dollar sign. I'm using the following code to remove dollar signs and validate the content: jQuery: $("#<%= tb.ClientID %>").change(function() { var ctrl = $("#<%= tb.ClientID %>"); ctrl.val(ctrl.val().replace('$','')) }); asp.net validation: <asp:CompareValidator ID="CompareValidator4" runat="server" Type="Double" ControlToValidate="tb" Operator="DataTypeCheck" ValidationGroup="vld_Page" ErrorMessage="Some error" /> My problem is that when someone enters a dollar sign in the TextBox "tb" and changes focus the validation happens first and THEN the jQuery removes the dollar sign. Is it possible to have the jQuery run first or to force the validation to run again after the jQuery executes?

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  • How to call a bool function...

    - by Gerri
    Hello, I did not see anything that address my particular code problem. I have a bool function in a class; the bool function is named: bool Triplet::operator ==(const Triplet& operand)const And I am trying to call it in Main but having problems just getting the call right. Apparently if I leave out any thing in the wording it gives an error that I have too few aruguments and if I try to use the entire wording of the function, I get the error that I need a semi-colon, but I already have a semi-colon at the end of the call, so I know that something else is wrong and I simply cannot figure out what is wrong! Any help would be appreciated! Thanks in advance.

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  • DeleteSubKey UnauthorizedAccessException

    - by Adam Haile
    I'm trying to write a quick app to modify some registry keys. When I'm browsing via RegEdit, I can modify and delete the keys with no problems. But when I try to use RegistryKey.DeleteSubKey() it throws an UnauthorizedAccessException Is there anyway to gain the privileges to do this? Also, why would there be a problem if my user account obviously has access to make the changes?

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  • I need to do a BASICE For Loop algorithm for a java Pyramid

    - by user1665119
    Question 2. USE THE FOR LOOP. Design and write an algorithm that will read a single positive number from the keyboard and will then print a pyramid out on the screen. The pyramid will need to be of a height equal in lines to the number inputted by the operator. Your program is not to test for negative numbers, nor is it to cater for them. For your test, use the number 7. If you would like to take the problem further, try 18 and watch what happens. Example input: 4 Example output: 1 121 12321 1234321

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  • What happens when a computer program runs?

    - by gaijinco
    I know the general theory but I can't fit in the details. I know that a program resides in the secondary memory of a computer. Once the program begins execution it is entirely copied to the RAM. Then the processor retrive a few instructions (it depends on the size of the bus) at a time, puts them in registers and executes them. I also know that a computer program uses two kinds of memory: stack and heap, which are also part of the primary memory of the computer. The stack is used for non-dynamic memory, and the heap for dynamic memory (for example, everything related to the new operator in C++) What I can't understand is how those two things connect. At what point is the stack used for the execution of the instructions? Instructions go from the RAM, to the stack, to the registers?

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  • How often do you implement the big three?

    - by Neil Butterworth
    I was just musing about the number of questions here that either are about the "big three" (copy constructor, assignment operator and destructor) or about problems caused by them not being implemented correctly, when it occurred to me that I could not remember the last time I had implemented them myself. A swift grep on my two most active projects indicate that I implement all three in only one class out of about 150. That's not to say I don't implement/declare one or more of them - obviously base classes need a virtual destructor, and a large number of my classes forbid copying using the private copy ctor & assignment op idiom. But fully implemented, there is this single lonely class, which does some reference counting. So I was wondering am I unusual in this? How often do you implement all three of these functions? Is there any pattern to the classes where you do implement them?

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  • MySQL Query WHERE Including CASE or IF?

    - by handfix
    Strange problem. My Query looks like SELECT DISTINCT ID, `etcetc`, `if/elses over muliple joined tables` FROM table1 AS `t1` # some joins, eventually unrelated in that context WHERE # some standard where statements, they work/ CASE WHEN `t1`.`field` = "foo" THEN (`t1`.`anOtherField` != 123 AND `t1`.`anOtherField` != 456 AND `t1`.`anOtherOtherField` != "some String") WHEN `t1`.`field` = "bar" THEN `t1`.`aSecondOtherField` != 12345 END #ORDER BY CASE etc. Standard Stuff Apperantly MySQL returns a wrong rowcount and I think my problem is in the logic of the WHERE ... CASE statement. Maybe with the brackets? Maybe I should go for operator OR and not AND? Should my the second WHEN include brackets also, even when I only compare one field? Should I use IF and not CASE? Basically I want to exclude some rows with specific values IF theres a specific value in field foo or bar I would try that all out, but it takes a huge amount of time to complete that query... :(

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