CODEWITHSUNDEEP
c++boostvectorstdboost-multi-array
DanS
DanS

Reputation: 183

Boost Multiarray of std::vector

I'm new to Boost (and also to stackoverflow) and want to use a multiarray of vectors. I have done it that way:

typedef boost::multi_array<std::vector<Vector3_t>, 2> array_type;
array_type* mImage;
int mResolution = 1000;
mImage = new array_type (boost::extents[mResolution][mResolution]);
//works  
mImage[0][0].origin()->push_back(Vector3_t());
//Error: abort()
mImage[1][1].origin()->push_back(Vector3_t());
//Error: abort()
mImage[500][440].origin()->push_back(Vector3_t());

On the internet I can only find examples of multiarray that use int,doule and so on. Is it possible to use a std::vector in a mutliarray ? I know I could use a 3d multiarray, but i would prefer vectors as elemet.

Upvotes: 1

Views: 1098

Answers (1)

Tanner Sansbury
Tanner Sansbury

Reputation: 51881

Boost.MultiArray supports std::vector elements. In general, Boost.MultiArray will perform concept checking at compile-time. Thus, if code compiles with the complete type, then it should be supported.

With mImage[0][0].origin():

  • mImage[0][0] returns a reference to std::vector<Vector3_t>.
  • origin() is not a member function on std::vector<Vector3_t>, resulting in an error.

origin() is a member function of multi-array, that returns the address of the first element's storage. In the case where the array has not been reindexed to a positive index, this is equivalent of 0 for all indexes (i.e. mImage.origin() == &mImage[0][0]).

Here is a brief and complete example with a multi-array of a vector of vector of ints.

#include <iostream>
#include <vector>

#include <boost/foreach.hpp>
#include <boost/range/counting_range.hpp>
#include <boost/multi_array.hpp>

int main()
{
  typedef std::vector<int> vector3_type;
  typedef boost::multi_array<std::vector<vector3_type>, 2> array_type;
  array_type array(boost::extents[5][5]);

  // Insert vector into multi-array.
  array[0][0].push_back(vector3_type());

  // Insert range of [100,105) into the first vector at [0][0] 
  BOOST_FOREACH(const int& i, boost::counting_range(100, 105))
    array[0][0].front().push_back(i);

  // Print all integers at [0][0][0]
  BOOST_FOREACH(const int& i, array[0][0][0])
    std::cout << i << std::endl;
}

And running produces the following expected output:

100
101
102
103
104

Upvotes: 3

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