copy element-only examples from bempp (#3)

* copy element-only examples from bempp

* fmt

* types::

examples/element_family.rs

@@ -0,0 +1,20 @@
+use ndelement::ciarlet::LagrangeElementFamily;
+use ndelement::traits::{ElementFamily, FiniteElement};
+use ndelement::types::{Continuity, ReferenceCellType};
+
+extern crate blas_src;
+extern crate lapack_src;
+
+fn main() {
+    // Create the degree 2 Lagrange element family. A family is a set of finite elements with the
+    // same family type, degree, and continuity across a set of cells
+    let family = LagrangeElementFamily::<f64>::new(2, Continuity::Continuous);
+
+    // Get the element in the family on a triangle
+    let element = family.element(ReferenceCellType::Triangle);
+    println!("Cell: {:?}", element.cell_type());
+
+    // Get the element in the family on a triangle
+    let element = family.element(ReferenceCellType::Quadrilateral);
+    println!("Cell: {:?}", element.cell_type());
+}

examples/lagrange_element.rs

@@ -0,0 +1,39 @@
+use ndelement::ciarlet::lagrange;
+use ndelement::{
+    traits::FiniteElement,
+    types::{Continuity, ReferenceCellType},
+};
+use rlst::{rlst_dynamic_array2, rlst_dynamic_array4, RawAccess};
+
+extern crate blas_src;
+extern crate lapack_src;
+
+fn main() {
+    // Create a P2 element on a triangle
+    let element = lagrange::create::<f64>(ReferenceCellType::Triangle, 2, Continuity::Continuous);
+
+    println!("This element has {} basis functions.", element.dim());
+
+    // Create an array to store the basis function values
+    let mut basis_values = rlst_dynamic_array4!(f64, element.tabulate_array_shape(0, 1));
+    // Create array containing the point [1/3, 1/3]
+    let mut points = rlst_dynamic_array2!(f64, [1, 2]);
+    points[[0, 0]] = 1.0 / 3.0;
+    points[[0, 1]] = 1.0 / 3.0;
+    // Tabulate the element's basis functions at the point
+    element.tabulate(&points, 0, &mut basis_values);
+    println!(
+        "The values of the basis functions at the point (1/3, 1/3) are: {:?}",
+        basis_values.data()
+    );
+
+    // Set point to [1, 0]
+    points[[0, 0]] = 1.0;
+    points[[0, 1]] = 0.0;
+    // Tabulate the element's basis functions at the point
+    element.tabulate(&points, 0, &mut basis_values);
+    println!(
+        "The values of the basis functions at the point (1, 0) are: {:?}",
+        basis_values.data()
+    );
+}