Constructors

Constructors of array

• The value classes array, matrix and vector have very similar constructors. We will therefore describe only for the array, and mention the difference for matrix and vector below.
• array, matrix, vector are regular types (with value semantics). Hence, all these constructors make a copy of the data, except of course the move constructor.

Constructors of array	Comments
array()	Empty array of size 0
array(size_t, …., size_t)	From the lengths of the array dimensions, with Rank arguments (checked at compile time).
array(const array &)	Copy construction
array(array &&)	Move construction
array(const T & X)	Type T models the ImmutableCuboidArray concept. - X must have the appropriate domain (checked at compile time). - Constructs a new array of domain X.domain() and fills it with evaluation of X.
array(shape_t const &)	New array with the corresponding shape (as returned by the function shape. See example in section XXX).
array(std::initializer_list<T>)	Initialization from a initializer_list of T. Enable for rank==1 only
explicit array(PyObject * X)	Construct a new array from the Python object X. - it takes a copy of the data of X (or of numpy(X)) into C++. - X is first transformed into a numpy by the python numpy lib itself (as if you call numpy.array(X)) if X is not a numpy array or an array of the wrong type (e.g. you construct an array<double,2> from a numpy of int….), and copied into the array. .. note: X is a borrowed reference, array does not affect its counting reference.

Warning

The constructor from the dimensions does NOT initialize the array to 0 (because it may not be optimal). If needed, do it explicitely by (a if the array) a()=0

Constructors of matrix

• matrix have similar constructors

Constructors of matrix	Comments
matrix()	empty matrix of size 0
matrix(size_t, size_t)	from the dimensions. Does NOT initialize the elements of matrix to 0 !
matrix(const matrix &)	copy construction
matrix(matrix &&)	move construction
matrix (PyObject * X)	Construct a new matrix from the Python object X.
matrix(const T & X)	Type T models the ImmutableMatrix or ImmutableCuboidArray (with rank 2). Same as array.

Constructors of vector

Constructors of vector	Comments
vector()	empty vector of size 0
vector(size_t)	from the dimensions. Does NOT initialize the elements of vector to 0 !
vector(const vector &)	copy construction
vector(vector &&)	move construction
vector (PyObject * X)	Construct a new vector from the Python object X.
vector(const T & X)	Type T models the ImmutableVector or ImmutableCuboidArray (with rank 1). Same as array.

Examples

#include <triqs/arrays.hpp>
using triqs::arrays::array;
using triqs::arrays::matrix;
using triqs::arrays::permutation;
using triqs::arrays::vector;
int main() {

  // A 3d array of long, C ordering, no option
  array<long, 3> A3(1, 2, 3);

  // A 2d array of double, C ordering, with explicit Bound Checking
  array<double, 2> B(1, 2);

  // a matrix of long
  matrix<long> M(2, 2);

  // a vector of double
  vector<double> V(10);

  // arrays with custom memory layout

  // C-style
  array<long, 3> A0(2, 3, 4);
  array<long, 3> A0b; // same type but empty

  // Fortran-style
  array<long, 3> A4(2, 3, 4, FORTRAN_LAYOUT);
  array<long, 3> A1b(FORTRAN_LAYOUT); // same type but empty

  // custom :  (i,j,k)  : index j is fastest, then k, then i
  array<long, 3> A2(2, 3, 4, triqs::arrays::make_memory_layout(1, 0, 2));
}