# How get data from vectors of templates?

Discussion in 'C++' started by Rob, Apr 15, 2008.

1. ### RobGuest

How would I do this?

I want to be able to handle vectors of many different types of data
and vectors that can contain any number of other vectors of data.

Currently, I have a templated function that handles vectors of vectors
of <typename T> (which could be anything from int to vectors of
something else). As well, I have specialized/overloaded functions to
handle the single-level vectors of data (e.g. vector<string>). So the
templated function only handles vectors of vectors of....whatever and
then as it loops down to the last vector of data, it "passes" it off

My problem is that the way I'm currently doing this creates extra
uselss objects and thus isn't clean/efficient. I can't seem to figure
out how to properly narrow down the vectors.

Code (Text):

vector<int>* convert(SomeClass obj)
{
//Return vector
vector<int>* retVector = new vector<int>();

//Get the values
int* values = ...elided...

//Put into vector
retVector->assign( values, values + length );

//Clean up
delete values;

return retVector;
}

vector<vector<int> >* convert(SomeClass obj, vector<int> spec)
{
//Length of array
int length = GetArrayLength( obj );

//Return vector
vector<vector<int> >* retVector = new vector<vector<int> >();

//Get all inner arrays
for ( int i = 0; i < length; i++ )
{
//Create an inner vector
vector<int>* innerVector;

//Now get the element of the outer SomeOtherClass Array
SomeOtherClass otherObj = ...elided...

//Set data
innerVector = convert( env, otherObj );

//Add it to the outer vector
retVector->push_back( *innerVector );

//Clean up
delete innerVector;
}

return retVector;
}

template <typename T>
vector<vector<T> >* convert(SomeClass obj, vector<T> spec)
{
//Length of array
int length = GetArrayLength( obj );

//Return array
vector<vector<T> >* T = new vector<vector<T> >();

//Set all inner arrays
for ( int i = 0; i < length; i++ )
{
//Create an inner vector
vector<T>* innerVector;

//use this to narrow down to eventually the specialized function
T subSpec;

//Now get the element
SomeOtherClass otherObj = ...elided...

//Convert inner data
innerVector = convert( env, otherObj, subSpec );

//Add it to the outer vector
T->push_back( *innerVector );

//Clean up refs
delete innerVector;
}

return T;
}

int main()
{
vector<vector<string> >* ret = convert( env, o2, vector<string>() );

//Print out results
for ( vector<vector<string> >::const_iterator it = ret->begin(); it !
= ret->end(); ++it )
{
vector<string> vec = *it;
for ( vector<string>::const_iterator vecIt = vec.begin(); vecIt !=
vec.end(); ++ivecIt )
{
printf( ( ( *vecIt ) + "\n" ).c_str() );
}
}
}

Rob, Apr 15, 2008

2. ### Fei LiuGuest

Rob wrote:
> How would I do this?
>
> I want to be able to handle vectors of many different types of data
> and vectors that can contain any number of other vectors of data.
>
> Currently, I have a templated function that handles vectors of vectors
> of <typename T> (which could be anything from int to vectors of
> something else). As well, I have specialized/overloaded functions to
> handle the single-level vectors of data (e.g. vector<string>). So the
> templated function only handles vectors of vectors of....whatever and
> then as it loops down to the last vector of data, it "passes" it off
> to the overloaded specialized functions.
>
> My problem is that the way I'm currently doing this creates extra
> uselss objects and thus isn't clean/efficient. I can't seem to figure
> out how to properly narrow down the vectors.
>

search 'blitz' or pythonArray for a discussion of multi-dimension array
implementation.

Fei

Fei Liu, Apr 15, 2008