ExpressionExtensionsTests.cs

using System.Linq.Expressions;

using MathCore.Extensions.Expressions;

namespace MathCore.Tests;

[TestClass]
public class ExpressionExtensionsTests
{
    public TestContext TestContext { get; set; }

    #region Additional test attributes

    // 
    //You can use the following additional attributes as you write your tests:
    //
    //Use ClassInitialize to run code before running the first test in the class
    //[ClassInitialize()]
    //public static void MyClassInitialize(TestContext testContext)
    //{
    //}
    //
    //Use ClassCleanup to run code after all tests in a class have run
    //[ClassCleanup()]
    //public static void MyClassCleanup()
    //{
    //}
    //
    //Use TestInitialize to run code before running each test
    //[TestInitialize()]
    //public void MyTestInitialize()
    //{
    //}
    //
    //Use TestCleanup to run code after each test has run
    //[TestCleanup()]
    //public void MyTestCleanup()
    //{
    //}
    //

    #endregion

    [TestMethod]
    public void TestSimpleFunction()
    {
        Expression<Func<double, double>> original_expression = t => t * t * t + 20;

        Expression<Func<double, double>> substitute_expression = t => t * t;

        var modified_expression = original_expression.Substitute("t", substitute_expression);

        var modified_function = (Func<double, double>)modified_expression.Compile();

        Assert.AreEqual(21, (int)modified_function(1));
        Assert.AreEqual(2 * 2 * 2 * 2 * 2 * 2 + 20, (int)modified_function(2));
    }

    [TestMethod]
    public void TestComplexPolynomial()
    {
        Expression<Func<double, double>> original_expression =
            t => (1 - t) * (1 - t) * (1 - t) * -50 +
                3 * (1 - t) * (1 - t) * t * -25 +
                3 * (1 - t) * t * t * 25 +
                t * t * t * 50;

        Expression<Func<double, double, double, double>> substitute_expression = (t, factor, shift) => t * factor + shift;

        var modified_expression = original_expression.Substitute("t", substitute_expression);

        var modified_function = (Func<double, double, double, double>)modified_expression.Compile();

        var result = modified_function(1, 10, -9);
        Assert.AreEqual(50, result);

        Console.WriteLine(original_expression);
        Console.WriteLine();
        Console.WriteLine(modified_expression);
    }
}