fork(1) download
copy 
  1. #include <cassert>
  2. #include <iostream>
  3. #include <vector>
  4.  
  5. template <typename ELEM>
  6. class NDArrayT {
  7.   private:
  8.     // dimensions
  9.     std::vector<size_t> _dims;
  10.     // data
  11.     std::vector<ELEM> _data;
  12.  
  13.   public:
  14.     NDArrayT(const std::vector<size_t> &dims):
  15.       _dims(dims)
  16.     {
  17.       size_t size = _dims.empty() ? 0 : 1;
  18.       for (size_t dim : _dims) size *= dim;
  19.       _data.resize(size);
  20.     }
  21.     NDArrayT(
  22.       const std::vector<size_t> &dims,
  23.       const std::vector<ELEM> &data):
  24.       NDArrayT<ELEM>(dims)
  25.     {
  26.       assert(_data.size() == data.size());
  27.       std::copy(data.begin(), data.end(), _data.begin());
  28.     }
  29.  
  30.     ELEM& operator[](const std::vector<size_t> &indices)
  31.     {
  32.       size_t i = 0, j = 0;
  33.       for (size_t n = _dims.size(); j < n; ++j) {
  34.         i *= _dims[j]; i += indices[j];
  35.       }
  36.       return _data[i];
  37.     }
  38.  
  39.     const ELEM& operator[](const std::vector<size_t> &indices) const
  40.     {
  41.       size_t i = 0, j = 0;
  42.       for (size_t n = _dims.size(); j < n; ++j) {
  43.         i *= _dims[j]; i += indices[j];
  44.       }
  45.       return _data[i];
  46.     }
  47. };
  48.  
  49. using namespace std;
  50.  
  51. ostream& operator<<(ostream &out, const vector<size_t> &values)
  52. {
  53.   const char *sep = "";
  54.   for (size_t value : values) {
  55.     out << sep << value; sep = ", ";
  56.   }
  57.   return out;
  58. }
  59.  
  60. bool inc(vector<size_t> &indices, const vector<size_t> &dims)
  61. {
  62.   for (size_t i = indices.size(); i--;) {
  63.     if (++indices[i] < dims[i]) return false;
  64.     indices[i] = 0;
  65.   }
  66.   return true; // overflow
  67. }
  68.  
  69. int main()
  70. {
  71.   // build sample data
  72.   vector<double> data(2 * 3 * 4);
  73.   for (size_t i = data.size(); i--;) data[i] = (double)i;
  74.   // build sample array
  75.   typedef NDArrayT<double> NDArrayDouble;
  76.   const vector<size_t> dims = { 2, 3, 4 };
  77.   NDArrayDouble a(dims, data);
  78.   // print sample array (check subscript)
  79.   vector<size_t> indices(dims.size(), 0);
  80.   do {
  81.     cout << "a[" << indices << "]: " << a[indices] << endl;
  82.   } while (!inc(indices, dims));
  83.   // done
  84.   return 0;
  85. }
Success #stdin #stdout 0s 4428KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
a[0, 0, 0]: 0
a[0, 0, 1]: 1
a[0, 0, 2]: 2
a[0, 0, 3]: 3
a[0, 1, 0]: 4
a[0, 1, 1]: 5
a[0, 1, 2]: 6
a[0, 1, 3]: 7
a[0, 2, 0]: 8
a[0, 2, 1]: 9
a[0, 2, 2]: 10
a[0, 2, 3]: 11
a[1, 0, 0]: 12
a[1, 0, 1]: 13
a[1, 0, 2]: 14
a[1, 0, 3]: 15
a[1, 1, 0]: 16
a[1, 1, 1]: 17
a[1, 1, 2]: 18
a[1, 1, 3]: 19
a[1, 2, 0]: 20
a[1, 2, 1]: 21
a[1, 2, 2]: 22
a[1, 2, 3]: 23
https://ideone.com/zDeweG
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!