2d vector error

[Lorn]

Hopefully someone can help me out with this problem I'm having with 2d
vectors. My vector initialization looks like this:

struct Object {
double d1;
double d2;
int i1;
};

std::vector<std ::vector <Object> > vMain;
std::vector<Obj ect> vec;

/////
When I add objects in the vectors it looks like this:

Object stData2 = { 2, 2, 2};
Object stData3 = { 3, 3, 3};
Object stData4 = { 4, 4, 4};

vec.push_back(s tData2);
vMain.push_back (vec);
vec.clear();
vec.push_back(s tData3);
vMain.push_back (vec);
vec.clear();

/////
Ok, so far so good. My problem comes when I want to add a third vector
object into my vMain vector at a specified position. The following
gives me an error:

vec.push_back(s tData4);
vMain[0].push_back(vec) ;

/////
The error I receive is:

error C2664: 'std::vector<_T y>::push_back' : cannot convert parameter 1
from 'std::vector<_T y>' to 'const CTestDlg::Objec t &'
with
[
_Ty=CTestDlg::O bject
]
and
[
_Ty=CTestDlg::O bject
]
Reason: cannot convert from 'std::vector<_T y>' to 'const
CTestAPIDlg::Ob ject'
with
[
_Ty=CTestDlg::O bject
]
No constructor could take the source type, or constructor
overload resolution was ambiguous.

/////

I have seen examples where the code above compiles and seemingly works.
What am I doing wrong? Any tips or suggestions would be very valuable
and much appreciated.

Thank you,
Lorn

[Marco Wahl]

Lorn wrote:

Hopefully someone can help me out with this problem I'm having with 2d
vectors.

vec.push_back(s tData2);
vMain.push_back (vec);
vec.clear();
vec.push_back(s tData3);
vMain.push_back (vec);
vec.clear();

/////
Ok, so far so good. My problem comes when I want to add a third vector
object into my vMain vector at a specified position. The following
gives me an error:

vec.push_back(s tData4);
vMain[0].push_back(vec) ;

Hi Lorn,

I just reduced/modified your code slightly. I suppose it becomes
cristal-clear
what the problem was.

#include <vector>

struct Object {
double d1;
double d2;
int i1;
};

int main(int argc, char* argv[])
{
std::vector<std ::vector <Object> > vMain;
std::vector<Obj ect> vec;
Object stData2 = { 2, 2, 2}; // This works? I'm surprised!
Object stData3 = { 3, 3, 3}; // But that doesn't matter for now.
Object stData4 = { 4, 4, 4};

vMain.push_back (vec);
vMain.push_back (vec);
vMain[0].push_back(vec) ; // Why this [0] here?

return 0;
}
Best wishes

[Ron Natalie]

Lorn wrote:

Hopefully someone can help me out with this problem I'm having with 2d
vectors. My vector initialization looks like this:

struct Object {
double d1;
double d2;
int i1;
};

std::vector<std ::vector <Object> > vMain;
std::vector<Obj ect> vec;

/////
When I add objects in the vectors it looks like this:

Object stData2 = { 2, 2, 2};
Object stData3 = { 3, 3, 3};
Object stData4 = { 4, 4, 4};

vec.push_back(s tData2);
vMain.push_back (vec);
vec.clear();
vec.push_back(s tData3);
vMain.push_back (vec);
vec.clear();

/////
Ok, so far so good. My problem comes when I want to add a third vector
object into my vMain vector at a specified position. The following
gives me an error:

vec.push_back(s tData4);
vMain[0].push_back(vec) ;

vMain[0] is type vector<Object>. Pushing back requires an argument of
type Object.

Why did you put vMain[0] here when you correctly used just vMain before?

[Lorn]

>vMain[0].push_back(vec) ; // Why this [0] here?

The reason for the zero is to specify the position in the vMain vector
where I would like to put the "vec" vector containing Object stData4.
Before the line you quoted there was 1 vector object in vMain[0] and 1
vector object in vMain[1]. It is basically a table. What I was trying
to do was add a second vector object at position vMain[0]. I have tried
multiple ways of doing this, but all give me the same error. For
example:

vMain.at(0).pus h_back(vec);

or

vMain.insert(vM ain.begin(), vec.begin(), vec.end()) // not sure about
this one, but I think it should be possible with correct formatting

Does anyone know if what I'm trying to do is a limitation of STL? Can a
vector<Object be added as I'm trying to do, or am I somehow having
problems with my compiler. Or, maybe just my code is wrong :).

Thanks

[Lorn]

Ahhhhh... ok, I get it. The correct notation here would be:

vMain[0].push_back(stDa ta4);

Thanks guys :-)

Lorn

[Ron Natalie]

Lorn wrote:

vMain[0].push_back(vec) ; // Why this [0] here?

The reason for the zero is to specify the position in the vMain vector
where I would like to put the "vec" vector containing Object stData4.
Before the line you quoted there was 1 vector object in vMain[0] and 1
vector object in vMain[1]. It is basically a table. What I was trying
to do was add a second vector object at position vMain[0]. I have tried
multiple ways of doing this, but all give me the same error. For
example:

push_back puts back at the end of the vector ALWSAYS. at(0)
or [0] returns an element of the vector.

If you want to insert, use insert:

vmain.insert(vm ain.begin(), vec);

or after the first position:
vmain.insert(vm ain.begin()+1, vec);

[Daniel T.]

In article <11************ **********@z14g 2000cwz.googleg roups.com>,
"Lorn" <ef*******@yaho o.com> wrote:

Hopefully someone can help me out with this problem I'm having with 2d
vectors. My vector initialization looks like this:

struct Object {
double d1;
double d2;
int i1;
};

std::vector<std ::vector <Object> > vMain;
std::vector<Obj ect> vec;
IMHO, don't do the above, your just making it hard on yourself (as you
are learning.) Create a Matrix class, if you know that each row will
have the same number of columns, then use a single vec internally, else
use a map.

template < typename T >
class RaggedMatrix {
typedef map< pair< int, int >, T > RepType;
RepType _rep;
public:
T& operator()( int x, int y ) {
return _rep[ make_pair(x, y) ];
}

const T& operator()( int x, int y ) const {
typename RepType::const_ iterator it = _rep.find( make_pair(x, y) );
if ( it == _rep.end() )
throw out_of_range("R aggedMatrix::op erator()(int, int)const");
return it->second;
}
};
/////
When I add objects in the vectors it looks like this:

Object stData2 = { 2, 2, 2};
Object stData3 = { 3, 3, 3};
Object stData4 = { 4, 4, 4};

vec.push_back(s tData2);
vMain.push_back (vec);
vec.clear();
vec.push_back(s tData3);
vMain.push_back (vec);
vec.clear();

With the above, you can easily add objects:

RaggedMatrix rMain;
rMain(0, 0) = stData2;
rMain(0, 1) = stData3;
rMain(1, 0) = stData4;

&c.
--
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nor does it profit by experiment. On the other hand, science is based
on experience; it is open to correction by observation and experiment.