CODEWITHSUNDEEP
c++boostmultidimensional-arrayboost-multi-array
saloua
saloua

Reputation: 2493

how to get specific elements from a const boost::multi_array

I would like to know how to read elements from a const boost::multi_array object. Indeed to my knowledge I can't use the operator [] because it's also used to assignement.

I have a 3-D dimentional array. So how does one get the element myArray[i][j][k] when myArray is const.

Upvotes: 0

Views: 761

Answers (2)

juanchopanza
juanchopanza

Reputation: 227418

You can read them by value or by const reference. Assuming your array holds elements of type T:

T x = myArray[1][2][3];
const T& y = myArray[1][2][3];

If you want a pointer to an element of the multi_array, then the pointer needs to be const:

const T* y = &myArray[1][2][3];

Upvotes: 2

janitor048
janitor048

Reputation: 2123

As an alternative to juanchopanza's answer you can also access elements via an index array build from a boost::array.

typedef boost::multi_array<double,3>::index tIndex;
typedef boost::array<tIndex, 3> tIndexArray;

tIndexArray index = {{ 1,2,3 }};
const double x = myArray( index );

Would give you the element myArray[1][2][3]. In case you are writing dimension-independent code this notation might be more useful than explicitly using the [] operator.

Upvotes: 2

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