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https://github.com/triqs/dft_tools
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50 lines
1.3 KiB
ReStructuredText
50 lines
1.3 KiB
ReStructuredText
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.. highlight:: c
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.. _Lazy:
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Interaction with clef expressions
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============================================
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* The Value and View classes (array, matrix and vector and algebraic expression of them)
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are ready to use with the triqs::clef library :
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* They can be called on lazy expressions made of placeholders.
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* Automatic assignment has been set up. Cf clef lib doc ...
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* Using the clef library offers a quick and efficient way to fill an array with multiple advantages :
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* It is simpler and more readeable than a series of for loops.
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* It is usually more optimal since the for loops are automatically written in the TraversalOrder of the
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array.
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* NB : the expression can be (and are) inlined by the compilers...
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* **Example** :
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.. compileblock::
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#include <triqs/arrays.hpp>
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using triqs::arrays::array; using triqs::clef::placeholder;
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int main(){
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placeholder<0> i_; placeholder<1> j_;
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array<double,2> A(2,2), B(2,2);
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A(i_,j_) << i_ + 2*j_ ;
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B(i_,j_) << A(j_,i_)/2;
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std::cout << "A = "<<A << std::endl;
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std::cout << "B = "<<B << std::endl;
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}
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.. note::
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The syntax uses a <<, not = since the array is not assigned to an expression
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but filled by the evaluation thereof.
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