Kehlet.Functional

Overview

Kehlet.Functional is a C# project focused on implementing functional programming constructs. This project provides a range of functionalities that are essential for functional programming paradigms in C#.

Examples

Monads

using static Kehlet.Functional.Prelude;

var number1 = ok(42);
var number2 = ok(69);
 
Result<int> result1 = from a in number1
                      from b in number2
                      select a + b;

Result<int> result2 = from a in number1
                      from b in number2
                      let sum = a + b
                      select sum > 50
                          ? ok(sum)
                          : error("Number is too low");

public Result<string> WriteFile(string projectName, string filePath, string content, FileWriteMode mode) =>
    from project in ParseProjectName(projectName)
    from file in ParseFilePath(project, filePath)
    let message = file.Exists ? "existing file" : "new file"
    select mode switch
    {
        FileWriteMode.Append => from result in fileSystem.AppendAllText(file.FullName, content) select $"Appended content to {message}: {file.Name}",
        FileWriteMode.Write => from result in fileSystem.WriteAllText(file.FullName, content) select $"Wrote content to {message}: {file.Name}",
        _ => error($"Unsupported mode: {mode}")
    };

LinqPlus

int factorial = from acc in fold(1)
                from value in (int[]) [1, 2, 3, 4, 5]
                select acc * value

Option<int> first = from n in (int[]) [1, 2, 3, 4]
                    select first(n > 2);

Option<int> last = from n in (int[]) [1, 2, 3, 4]
                   select last();

IEnumerable<int> take3 = from n in (int[]) [1, 2, 3, 4]
                         select take(3);

IEnumerable<int> take = from n in (int[]) [1, 2, 3, 4]
                        select takeWhile(n < 3);

Option<(string, float)> last = from student in students
                               from grade in student.Grades
                               select (student.Name, grade) into studentGrades
                               select reverse() into reversed
                               select first();