Evaluators and modifiers are two of the main concepts of MGIS/Function (see this page for an introduction).

Unary modifiers

• view: the view modifier takes a dynamic function or evaluator and return an evaluator with a fixed number of components. The view modifier takes the expected number of components as argument.

  // take a view on some values with a runtime size
  const auto f = FunctionEvaluator<BasicLinearSpace>(space, values, 1);
  // make a view with a fixed number of components and apply the `transform` modifier
  const auto e = view<1>(f) | transform([](const real x) { return x * x; });

• negate: the view modifier takes an evaluator which returns opposite values of the initial evaluator.

  const auto f =
      FunctionEvaluator<BasicLinearSpace>(space, values, 2) | as_tvector<2>;
  const auto n = f | negate;

Modifiers’s generators

• multiply_by_scalar: the multiply_by_scalar takes an real number \(alpha\) and returns a modifier which takes an evaluator and returns an evaluator which multiplies the values of the original evaluator bu \(\alpha\):

  const auto e = f | multiply_by_scalar(4);

• divide_by_scalar: the divide_by_scalar takes an real number \(alpha\) and returns a modifier which takes an evaluator and returns an evaluator which divides the values of the original evaluator bu \(\alpha\):

  const auto e = f | divide_by_scalar(4);

Tensors

This section is devoted to modifiers related to tensors.

Views

• as_scalar: create an evaluator which returns a scalar.

  const auto s = f | as_scalar;

• as_stensor: create an evaluator which returns symmetric tensorial values. This modifier takes an integer as template parameter, the space dimension.

  const auto trace_values = f2 | as_stensor<2> | trace;

• as_tensor: create an evaluator which returns unsymmetric tensorial values. This modifier takes an integer as template parameter, the space dimension.

• as_fsarray: create an evaluator which returns an (finite size) array. This modifier takes an integer as template parameter, the size of the array.

• as_tvector: create an evaluator which returns vectorial values. This modifier takes an integer as template parameter, the size of the vector.

• as_matrix: create an evaluator which returns matrix values. This modifier takes two integers as template parameters: the number of rows and the number of columns.

Modifiers on tensor-valuated evaluators

• eigen_values: modifier creating an evaluator of the eigen values. The evaluator on input must return symmetric tensor values.
• trace:
• det:

Modifiers dedicated to mechanics

• hydrostatic_stress: modifier creating an evaluator of the hydrostatic pressure \(p\) defined as:

  \[ p = \mathrm{trace}\left(\underline{\sigma}\right/3 \]

• vmis: modifier creating an evaluator of the von Mises stress.

• principal_stress: modifier creating an evaluator of the principal stress. This is an alias for the eigen_values modifier

Binary modifiers

• add:
• substract:
• multiply:
• divide:
• mean_value:
• inner_product:

Binary modifiers on tensor-valuated evaluators

• rotate:
• rotate_backwards:

Binary modifiers dedicated to mechanics

• from_pk1_to_cauchy: