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  • Can C++ Constructors be templates?

    - by Gokul
    Hi, I have non-template class with a templatized constructor. This code compiles for me. But i remember that somewhere i have referred that constructors cannot be templates. Can someone explain whether this is a valid usage? typedef double Vector; //enum Method {A, B, C, D, E, F}; struct A {}; class Butcher { public: template <class Method> Butcher(Method); private: Vector a, b, c; }; template <> Butcher::Butcher(struct A) : a(2), b(4), c(2) { // a = 0.5, 1; // b = -1, 1, 3, 2; // c = 0, 1; } Thanks, Gokul.

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  • MSSQL Sum query

    - by ldb
    today my problem is this i have 2 column and i wish check if the sum of that columns isn't Higher then a value(485 for example) and if is do a query...i though to do SELECT * FROM table WHERE ColumnA+ColumnB<485 But isn't working... i've already tried with SELECT Sum(ColumnA)+Sum(ColumnB) AS Total FROM table but it gives me 1 column with the sum of all rows, i instead want a row for every sum. so how can i do..? xD i hope you understood if not just ask that i try to explain it better! and thanks in advice for who want to help me! EDIT: I Found out XD the problem was that the columns was Smallint and the result of 1 or more rows was more than 32k so it wasn't working! Thanks At all!!

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  • Float32 to Float16

    - by Goz
    Can someone explain to me how I convert a 32-bit floating point value to a 16-bit floating point value? (s = sign e = exponent and m = mantissa) If 32-bit float is 1s7e24m And 16-bit float is 1s5e10m Then is it as simple as doing? int fltInt32; short fltInt16; memcpy( &fltInt32, &flt, sizeof( float ) ); fltInt16 = (fltInt32 & 0x00FFFFFF) >> 14; fltInt16 |= ((fltInt32 & 0x7f000000) >> 26) << 10; fltInt16 |= ((fltInt32 & 0x80000000) >> 16); I'm assuming it ISN'T that simple ... so can anyone tell me what you DO need to do?

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  • Why can I derived from a templated/generic class based on that type in C# / C++

    - by stusmith
    Title probably doesn't make a lot of sense, so I'll start with some code: class Foo : public std::vector<Foo> { }; ... Foo f; f.push_back( Foo() ); Why is this allowed by the compiler? My brain is melting at this stage, so can anyone explain whether there are any reasons you would want to do this? Unfortunately I've just seen a similar pattern in some production C# code and wondered why anyone would use this pattern.

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  • How to use #ifdef entities as part of functions in header files

    - by Crazyjavahacking
    I would like to ask if it is possible to use the entities defined in #ifdef block in header files. To be clear, I have following code: #ifdef #include <winsock2.h> #define SOCKET_HANDLE SOCKET #define CONNECTION_HANDLE SOCKET #endif SOCKET_HANDLE createServerSocket(const char* hostAddress, short port); I am Java developer and this seems completely fine for me. However compiler has a problem with this. Can you explain why is that code a problem? Also how can I force to compile it. (The idea is to have generic interface and conditional compilation to determine real types according to running platform at compile time.) Thanks

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  • c++ signatures, pointers

    - by coubeatczech
    Hello, what's the difference between these signatures? T * f(T & identifier); T & f(T & identifier); T f(T & identifier); void f(T * identifier); void f(T & identifier); void f(T identifier); I met pointers in c, but the amperstand in function signature is new for me. Can Anyone explain this?

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  • Uploading or writing to files contained within s3

    - by Chase
    We have a widget that needs to be hosted on s3 due to a bunch of hoopla that isn't relevant to the issue. I'd explain if it was worth the time. Problem is it calls an external XML file for part of its content. The XML file is accessible if it is local on s3 but I cannot get my php file to write to it on s3. The widget could also be useful if I could access the xml file elsewhere but s3 does not seem to permit this. Suggestions? Here's the error I'm getting when trying to write to S3. [function.fopen]: failed to open stream: HTTP wrapper does not support writeable connections.

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  • how to cast an array of char into a single integer number?

    - by SepiDev
    Hi guys, i'm trying to read contents of PNG file. As you may know, all data is written in a 4-byte manner in png files, both text and numbers. so if we have number 35234 it is save in this way: [1000][1001][1010][0010]. but sometimes numbers are shorter, so the first bytes are zero, and when I read the array and cast it from char* to integer I get wrong number. for example [0000] [0000] [0001] [1011] sometimes numbers are misinterpreted as negative numbers and simetimes as zero! let me give you an intuitive example: char s_num[4] = {120, 80, 40, 1}; int t_num = 0; t_num = int(s_num); => 3215279148 ?????? the result should be 241 but the output is 3215279148? I wish I could explain my problem well! how can i cast such arrays into a single integer value?

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  • strtok program crashing.

    - by baskin
    Hi, the program for strtok given on http://www.opengroup.org/onlinepubs/000095399/functions/strtok.html crashes everytime.. #include <string.h> ... char *token; char *line = "LINE TO BE SEPARATED"; char *search = " "; /* Token will point to "LINE". */ token = strtok(line, search); /* Token will point to "TO". */ token = strtok(NULL, search); If I use a char array for variable 'line', it works. i.e. char line[] = "LINE TO BE SEPARATED" works. Kindly explain.

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  • Trouble using xib files in libraries

    - by flohei
    Hi there, I'm having some trouble working with libraries and included xib files. Let me explain my situation first. I've got a project that's running pretty good. Now I need a part of my project as a library for another customer who want's to use some of the functionality in his app. I've created a library with help of that highly recommended article. My customer should be able to initialize a main view controller like this: LibraryMainViewController *lmvc = [[LibraryMainViewController alloc] initWithNibName:@"LibraryMainViewController.xib" bundle:foo]; That for sure leads to an error when I try to present that view controller modally. I'm not sure what bundle I have to use here. I tried something like [NSBundle bundleForClass:[SomeClassInTheLibrary class]]; but that didn't solve the problem. I would be glad if someone could tell me how to actually use a xib file in that kind of situation. Thanks –f

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  • Displaying same icon in 2 different sizes on c#

    - by ET
    My goal is to display the same icon twice, but each time in different size. I tried the following: FileStream fs = new FileStream("name_of_the_icon_file.ico", FileMode.Open); Icon ico = new Icon(fs, 32, 32); //create an in-memory instance of the icon, size 32x32 Icon ico2 = new Icon(fs, 16, 16); //create an in-memory instance of the icon, size 16x16 ... Graphics.DrawIcon(ico, /*some point*/); Graphics.DrawIcon(ico2, /*some other point*/); The last line throws an ArgumentException: Value does not fall within the expected range. Can some one explain me whats wrong and whats the way to do this right?

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  • What is the difference between an object's scope and it's context in javascript?

    - by DKinzer
    In the vernacular, scope and context have a lot in common. Which is why I get confused when I read references to both, such as in the quote below from an article on closures: Scope refers to where variables and functions are accessible, and in what context it is being executed. (@robertnyman) As far as I can tell, context is just a reference to an object. Can someone please explain what exactly is context, as used, for instance, in the jQuery syntax, $(selector, context). And is an object's scope the same at it's context?

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  • What does addListener do in node.js?

    - by Jeffrey
    I am trying to understand the purpose of addListener in node.js. Can someone explain please? Thanks! A simple example would be: var tcp = require('tcp'); var server = tcp.createServer(function (socket) { socket.setEncoding("utf8"); socket.addListener("connect", function () { socket.write("hello\r\n"); }); socket.addListener("data", function (data) { socket.write(data); }); socket.addListener("end", function () { socket.write("goodbye\r\n"); socket.end(); }); }); server.listen(7000, "localhost");

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  • How to interpret situations where Math.Acos() reports invalid input?

    - by Sean Ochoa
    Hey all. I'm computing the angle between two vectors, and sometimes Math.Acos() returns NaN when it's input is out of bounds (-1 input && input 1) for a cosine. What does that mean, exactly? Would someone be able to explain what's happening? Any help is appreciated! Here's me method: public double AngleBetween(vector b) { var dotProd = this.Dot(b); var lenProd = this.Len*b.Len; var divOperation = dotProd/lenProd; // http://msdn.microsoft.com/en-us/library/system.math.acos.aspx return Math.Acos(divOperation) * (180.0 / Math.PI); }

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  • Understanding "this" keyword

    - by Raffaele
    In this commit there is a change I cannot explain deferred.done.apply( deferred, arguments ).fail.apply( deferred, arguments ); becomes deferred.done( arguments ).fail( arguments ); AFAIK, when you invoke a function as a member of some object like obj.func(), inside the function this is bound to obj, so there would be no use invoking a function through apply() just to bound this to obj. Instead, according to the comments, this was required because of some preceding $.Callbacks.add implementation. My doubt is not about jQuery, but about the Javascript language itself: when you invoke a function like obj.func(), how can it be that inside func() the this keyword is not bound to obj?

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  • I can't Distinct, Sum, or Count from 3 tables with group clauses

    - by Rio Inggit Dharmawangsa
    I'm still learning linq, now i'm getting confused. I need data for report from 3 tables, I get the result, but it's duplicate. I have used distinct but it's not working, n I need data to be sum still not working. Here is my query, can somebody explain what's wrong? var report= (from u in myDb.TBL_TRANSAKSI_MKN_MNMs.AsEnumerable() where u.TGL_TRANSAKSI.Value.Date.Equals(dateTimePicker1.Value.Date) join l in myDb.TBL_DETAIL_TRANSAKSIs.AsEnumerable() on u.ID_NOTA equals l.ID_NOTA join m in myDb.TBL_MKN_MNMs.AsEnumerable() on l.ID_MKN_MNM equals m.ID_MKN_MNM group new { u, l, m } by new { m.NAMA_MKN_MNM, m.HARGA_JUAL, u.TGL_TRANSAKSI, l.ID_MKN_MNM, u.USERNAME, l.Jumlah } into grp select new { MakanMinum = grp.Key.NAMA_MKN_MNM, HargaJual = grp.Key.HARGA_JUAL, Stok = grp.Sum(groupedthing => groupedthing.l.Jumlah), Tanggal = grp.Key.TGL_TRANSAKSI, Jumlah =(grp.Key.HARGA_JUAL * grp.Sum(groupedthing => groupedthing.l.Jumlah)), Total = grp.Sum(grouptotal => grp.Key.HARGA_JUAL * grp.Sum(groupedthing => groupedthing.l.Jumlah)), Username = grp.Key.USERNAME }).Distinct();

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  • How messages flows between computers connected with Internet or LAN ?

    - by Praveen
    Hi All, I have been doing Windows programming in .Net since last two years. Now I am shifting to web programming so I just stuck in understanding the fundamentals of web programming, after googling I came to StackOverflow to learn from all of you great guys. My confusion is about how messages flow between systems in distributed enviornment ? I mean suppose I want to send a message "Hello" to a system connected to LAN or Internet, then what will be the steps taken to send the message. Second thing is suppose my system is "A" and I wana send message to system "B" which is connected via a wire, so how the message flows on wire and how system "B" reads it from the wire ? Please someone explain me in a layman terms. Thank you all in advance.

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  • Not a statement?

    - by abelenky
    I have a simple little code fragment that is frustrating me: HashSet<long> groupUIDs = new HashSet<long>(); groupUIDs.Add(uid)? unique++ : dupes++; At compile time, it generates the error: Only assignment, call, increment, decrement, and new object expressions can be used as a statement HashSet.Add is documented to return a bool, so the ternary (?) operator should work, and this looks like a completely legitimate way to track the number of unique and duplicate items I add to a hash-set. When I reformat it as a if-then-else, it works fine. Can anyone explain the error, and if there is a way to do this as a simple ternary operator?

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  • Constant Assigment Bug in Ruby?

    - by aronchick
    We caught some code in Ruby that seems odd, and I was wondering if someone could explain it: $ irb irb(main):001:0> APPLE = 'aaa' => "aaa" irb(main):002:0> banana = APPLE => "aaa" irb(main):003:0> banana << 'bbb' => "aaabbb" irb(main):004:0> banana => "aaabbb" irb(main):005:0> APPLE => "aaabbb" Catch that? The constant was appended to at the same time the local variable was. Known behavior? Expected?

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  • page_load another handler?

    - by joe doe
    can someone please explain why this code is not working as expected: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; public partial class temp : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Response.Write("foo<br>"); this.Load += new EventHandler(temp_Load); } void temp_Load(object sender, EventArgs e) { Response.Write("bar<br>"); Response.End(); } } trying to add another handler for page Load event so that output would be: foo<br> bar<br>

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  • Could someone tell me if my C++ indent style is named? (example given)

    - by Maulrus
    I'm learning C++. For me, my programming style is just what looks the best; it doesn't seem to follow the rules of any one particular style. Here's an example void f(int x){ //no space between close-paren and bracket if (!x){ cout << "x is non-zero\n"; } //closing bracket indented to the same level as the original statement } It's only slightly different for something like a class or a namespace: class myClass {}; //space between class name and bracket, otherwise the same as functions K&R style does uses that kind of bracketing for statements, but my style uses it for everything. I'd like to know if there's a name for it so I can say simply what my indent style is without having to explain using examples like these.

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  • Path with no slash after drive letter and colon - what does it point to?

    - by ya23
    I have mistyped a path and instead of c:\foo.txt wrote c:foo.txt. I expected it to either fail or to resolve to c:\foo.txt, but instead it seems to be resolved to foo.txt in a current user's home folder. Powershell returns: PS C:\> [System.IO.Path]::GetFullPath("c:\foo.txt") c:\foo.txt PS C:\> [System.IO.Path]::GetFullPath("c:foo.txt") C:\Users\Administrator\foo.txt PS C:\> [System.IO.Path]::GetFullPath("g:foo.txt") G:\foo.txt Running explorer.exe from commandline and passing it any of the above results in C:\Users\Administrator\Documents to be opened. I haven't found any documentation of that and I'm utterly confused, please explain the behaviour.

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  • Simple OOP-related question.

    - by M4design
    This question came to my mind quite a few times. Let my explain my question through an example. Say I've got two classes: 1- Grid. 2- Cell. Now the location of the cell 'should' be stored in the grid class, not in the cell class itself. Say that the cell wanted to get its location through a method in the grid. How can it do that? Keep in mind that the cell was created/initialised by the Grid class. What good OO approach to solve this problem? Thank you

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  • Htaccess/robots.txt to allow search bots to explore main domain but not directory on other domain

    - by gX
    Ok, I understand the Title didn't make any sense so here I've tried to explain it in detail. I'm using a hosting that gives me space for my domain and lets me "add on" other domains on it. So lets say I have a domain A, and I add on a domain B. Basically my hosting gives me a public_html where I can put stuff that shows when someone visits website A. But, when I add the domain B, it lets me put the content of B, INSIDE of that public_html so that website B.com can also be visited by going to A.com/siteB... Thats all good, except that Google has started indexing B.com as well as A.com/siteB, I'm ok with it indexing B.com, but I somehow want to prevent it from indexing A.com/siteB so that when people search for B, it doesn't end up showing A.com/siteB. Any ideas? Let me know if the question is still unclear.

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  • Why does Perl allow mutual "use" relationships between modules?

    - by Haiyuan Zhang
    Let's say there are two modules that mutually use each other: package a; use b; sub p {} 1; package b; use a; 1; I think that it is systematically wrong to write code like the above, because the two modules will endlessly copy each other's code to themselves, but I can successfully run the following code, which makes me very surprised. Could any of you explain all of this to me? #! /usr/bin/perl use a; a->p();

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