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Hi guys
Before my question I remind you I'm an amateur... so be kind in your response
Why is it that the following code works fine if I use a regular array and not a vector container... How do I make the function return a pointer to the beginning of the vector and use it on the call from another function...???
Thanks a lot for all your help, you guys are great!
double *TakeThisVector::CreateVector(double such)
{
vector<double> A_vector;
double *pt_tovector = 0;
int max=2;
for(int i=0; i<= max; i++)
{
A_vector.push_back(such);
such++;
}
pt_tovector = A_vector;
return pt_tovector;
}
void GimmeTheVector::ShowVector()
{
TakeThisVector TTV;
double A0, A1;
double *Recover = 0;
Recover = TTV.CreateVector(Lat, Lon);
A0 = *Recover++;
A1 = *Recover;
}
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You would return &A_vector[0]...except that A_vector doesn't exist after CreateVector exits.
You probably want to return the vector rather than a pointer to its first element.
Stuart Dootson
'Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p'
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uh... pt_tovector IS &A_vector[0]... and the code works if instead of using a vector container I use an array. The error message is:
error C2679: binary '=' : no operator defined which takes a right-hand operand of type 'class std::vector<double,class std::allocator<double=""> >' (or there is no acceptable conversion)
which means that I can't assign &A_vector[0] to pt_tovector if A_vector is a container...
...or I'm more confused than I thought
Thanks!!!
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knapak wrote:
uh... pt_tovector IS &A_vector[0]
No, the code you posted has pt_tovector = A_vector; . For ordinary arrays that would be same as pt_tovector = &A_vector[0]; but not for vectors.
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OHHHHHHHH .... So.... how do I solve the problem? The first comments suggest to return the vector itself instead of a pointer to its first element... EXCUSE MY NAIVETE, but I always thought that returning a pointer to the first element of an array was THE way to return an array... Of course now we are talking about Vectors...
Thank you!
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OK... so I figured that if I make an iterator be A_vector.begin() and then pass the iterator to a pointer... should do the trick... right? WRONG!
That works within the scope of the function that contains the vector, but apparently the container dissapears as the program exits the function call (just as the first folk said). That obviously is different to what happens when using regular arrays... and still have not found the way to do what I need...
Many thanks to all of you.
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As I said in my first reply, return the vector object - otherwise the storage associated with the vector is deallocated when the function exits.
If you did a similar thing with arrays, like below, you'd have the same problem.
double *CreateArray(double such)
{
double pt_tovector[2];
pt_tovector[0] = such;
pt_tovector[1] = such;
return pt_tovector;
}
Of course, if you allocated the array on the heap like the example below, you *CAN* return the array pointer. The thing is, the vector encapsulates and manages a pointer to heap storage - if you think of the vector as a pointer to an array in heap storage with other useful properties (like knowing how big the array is - a pointer won't tell you that), that may help.
double *CreateArray(double such)
{
double* pt_tovector = new double[2];
pt_tovector[0] = such;
pt_tovector[1] = such;
return pt_tovector;
}
BTW - iterators in VC7.1 are not pointers. They were in VC6, but there is no guarantee that iterators are pointers.
Stuart Dootson
'Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p'
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Hello everyone
First and foremost, THANKS TO ALL OF YOU WHO PROVIDED AN ANSWER/OPINION. I'm learning a lot.
Now, as an academic curiosity, I think that if I make a vector container available outside the function (by making it global), then it should be equivalent to using:
double* pt_tovector = new double[2];
without deallocating the memory at the end of the function. Memory will remain caught until the program exits which is something I need to avoid since my code is big. In which case, since for this particular example I only need to retrieve two values, I rather make the whole function void with the two values of interest private and then include a couple of tiny accessor functions, one for each value... is this solution too ugly a programming style???
Many thanks again!!!
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Yes, you should return a pointer to the first element of the vector, but your code doesn't do that! You must actually write pt_tovector = &A_vector[0] in your program to return a pointer to the first element of the STL vector A_vector . Additionally, the vector can't be local to the function.
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Can someone show me how to send (save/Write) and receive (load/Read) data contained in a map and/or vector. class CData{ public: string one, two, three; CData() {}; ~CData() {} };
the map is declared as: map<string CData> DATA; How do I read/write it's data to a file ("MyMapFile.dat") ???
vector<CData> vecDATA; how do I read/write it's data to a file("MyVecDATA.dat") ???
I'm new to the STL and would need explicit examples that are known to work properly PLEASE.
C++ is my favorite programming language
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You cannot automatically serialize STL objects to files. You must write your own file format. If you use only MFC then you can use CArray and CMap as containers and serialize with CArchive.
Regards,
Alexandru Savescu
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Is it possible to get the title that is enclosed in the html as <title>My webpage</title>?
I have found that IWebBrowser2 have the GetProperty method, what are the properties of the page that we can get?
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IWebBrowser2->GetDocument() will return the the docuement interface of the Loaded page.
wait a min i demonstrate that by code
<br />
IHTMLElementCollection *pColl=NULL;<br />
IHTMLElement *pEle=NULL;<br />
<br />
m_HtmDom->get_all(&pColl);<br />
MessageBox("yeah");<br />
<br />
CComVariant varTitle("title");<br />
CComVariant varIndex(0);<br />
IDispatch *pDisp;<br />
<br />
pColl->item(varTitle,varIndex,&pDisp);<br />
MessageBox("yeah1");<br />
<br />
if(pDisp)<br />
pDisp->QueryInterface(IID_IHTMLElement,(LPVOID*)&pEle);<br />
<br />
MessageBox("yeah3");<br />
if(pEle)<br />
{<br />
BSTR p;<br />
pEle->get_innerText(&p);<br />
MessageBoxW(NULL,p,L"",NULL);<br />
}
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
cheers,
Alok Gupta
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Modern programmers don't use nature and science for making programs. I am use. You may to make big and fast programs. There is no other solution.
<http: luckyware.tripod.com="">
Luckyware-tripod-com
Sory. E-Mail don't readed.
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Don't drink and post
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Abecedarian wrote:
Don't drink
iS he a Drinker!
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
cheers,
Alok Gupta
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so what ? that's all ???
i'm quite sure you don't even know anything on what you are talking about...
you've got my vote : 1 !
... ok, move on now
TOXCCT >>> GEII power [toxcct][VisualCalc]
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Hi
Can we use templates with variable argument list. Plz help me if anybody has the solution.
Thanks and Regards
Siji
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The short answer is no. The long answer is no, but you can fake this feature. For instance, the following creates the illusion of a class template allowing for an arbitrary number of type parameters up to 10:
struct void_arg{};
template <
typename T0=void_arg,
typename T1=void_arg,
typename T2=void_arg,
typename T3=void_arg,
typename T4=void_arg,
typename T5=void_arg,
typename T6=void_arg,
typename T7=void_arg,
typename T8=void_arg,
typename T9=void_arg
>
class my_template
{
...
};
...
typedef my_template<int,char,double> foo; Note that void_arg is used as a marker meaning "no parameter specified". Now, the real problem is how to handle the variable number of parameters to do something useful: this will lead you to the realm of template metaprogramming (google for that.) Two libraries in Boost[^] named Boost.TypeTraits[^] and Boost MPL[^] are commonly used for doing template metaprogamming (beware, this is non-trivial stuff.)
If you have a specific problem where you want to take advantage of a variable number of template parameters, please post what you've got here and I can try to help a little.
Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo
Want a Boost forum in Code Project? Vote here[^]!
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There is an interesting technique for simulating this feature described in this book[^] Maybe you can find the example on the book's web site.
My programming blahblahblah blog. If you ever find anything useful here, please let me know to remove it.
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I have a WTL based application. In response to a particular user action, it is to create and show a new CFrameWindowImpl<> based window that includes a splitter and two client windows. This all works fine on my development computer. It does not work when I distribute to the computer that this application is suppose to be run on.
On the other computer, the two client windows are not being painted. Both computers are running Win2000 Service Pack 3.
Any clues?
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