Assignment to views

Synopsis:

template<typename RHS> array_view & operator=(RHS const & X);

NB: The assignment operator is deleted for const_views.

The view classes have a quite general assignment operator. We will illustrate it on the array_view class, it is the same for matrix and vector.

• RHS can be:

  • Anything that models the ImmutableCuboidArray concept

    e.g.: array, array_view, matrix, matrix_view, but also formal expression (See , e.g. A+B), or any custom object of your choice.

    Effect:

    Every elements viewed by the view are replaced by the evaluation of RHS.

    Precondition

    The shape of the view and of RHS must match exactly or behaviour is undefined.

    If the debug macro, TRIQS_ARRAYS_ENFORCE_BOUNDCHECK is defined, this condition is checked at runtime.

    NB: We could lower this condition, since we don’t need a domain here, just the evaluation on the indices…

  • A scalar.

    Effect:

    Every elements viewed by the view are set to this scalar, except for the matrix_view, where the matrix is set to the identity.

NB: no move assignment operator

Note that there is no move assignment operators for views. If RHS is an rvalue documentation/manual/triqs, the regular operator= (view const &) is called, that makes a copy of the data of RHS into the elements viewed by the view.

This behaviour is consistent with the fact that views are not regular types. For example

array<double,2> A(3,3);
A(range(0,2), range(0,2)) = any_function_returning_a_new_2x2_array(....);

In this case, the expected behaviour is that the part of A views by view at l.h.s is filled by the result of the function. There cannot be any move semantics here.

As a result, std::swap algorithm does not work properly for view, hence it has been explicitely deleted. A swap function (found by ADL) is provided instead.