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dft_tools/doc/reference/c++/arrays/lazy.rst
Olivier Parcollet 1a85f5a16c Work on doc
2013-09-11 18:38:18 +02:00

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.. highlight:: c
.. _Lazy:
Interaction with CLEF expressions
============================================
* The containers and their view classes can be used with the :doc:`../clef/contents` library :
* They can be called with CLEF expressions.
* :doc:`Automatic assignment<../clef/assign>` has been set up.
* Using the CLEF library offers a quick and efficient way to fill an array with multiple advantages :
* It is simpler and more readeable than a series of for loops.
* It is usually more optimal since the for loops are automatically written in the TraversalOrder of the array.
* **Example** :
.. compileblock::
#include <triqs/arrays.hpp>
using triqs::arrays::array; using triqs::clef::placeholder;
int main(){
placeholder<0> i_; placeholder<1> j_;
array<double,2> A(2,2), B(2,2);
A(i_,j_) << i_ + 2*j_ ;
B(i_,j_) << A(j_,i_)/2;
std::cout << "A = "<<A << std::endl;
std::cout << "B = "<<B << std::endl;
}
.. note::
The syntax uses a <<, not = since the array is not assigned to an expression
but filled by the evaluation thereof.