Finite Element Assembly Using an Embedded Domain Specific Language

Listing 3

Grammar capable of parsing a simple expression for interpolating coordinates using a shape function.

()  struct fem_grammar:

()   // Match the following rules in order:

()   proto::or_

()   <

()    // Evaluate shape functions using the eval_shape_func transform

()    proto::when

()    <

()     proto::terminal<shape_func_tag>,

()     eval_shape_func(proto::_data)

()  >,

(1)  // Evaluate transpose expressions using eval_transpose

(2)  proto::when

(3)  <

(4)   proto::function<proto::terminal<transpose_tag>, fem_grammar >,

(5)   eval_transpose(fem_grammar(proto::_child1))

(6)  >,

(7)  // Evaluate element_quadrature using eval_element_quadrature

(8)  proto::when

(9)  <

()   proto::function< proto::terminal<element_quadrature_tag>, proto::plus_assign<proto::

        terminal<Eigen::MatrixXd>, fem_grammar> >,

()   eval_element_quadrature(proto::_value(proto::_left(proto::_child1)),

        proto::_right(proto::_child1), proto::_data)  

()  >,

()  // On any other expression: perform the default C++ action

()  proto::_default<fem_grammar>

() >

() {

() };