Exploring Haskell: a dive into its use cases and comparison with other languages
Introduction
Working through the course Haskell MOOC has been an educational experience, introducing me to the world of functional programming through the robust Haskell language. The course, designed for both beginners and even those familiar with functional programming, has provided a comprehensive foundation in Haskell, covering everything from basic syntax to advanced features like higher-order functions and algebraic data types.
The course: Haskell MOOC
The course itself is divided into two individual large parts. It includes an excellent free online course material with examples and exercises.
Working on the exercises involves knowing how to use the command line, and basic usage of the Git version control system.
There are two parts with a total of 16 lectures. Part 1 covers the basics of Haskell syntax and features sticking to pure functional programming, without side-effects. I/O (input-output) and Monads will be introduced in Part 2.
monad: a design pattern used to handle computations in a sequence. It allows for chaining operations while managing side effects, encapsulating values, and providing a way to apply functions to these values.
All 16 lectures are roughly the same size, but some have more material than others. Each lecture set ends with 10-30 small programming exercises on the topics of the lecture. The course is completed by solving all the exercises.
Example of an exercise:
------------------------------------------------------------------------------
-- Ex 3: implement the Euclidean Algorithm for finding the greatest
-- common divisor:
--
-- Given two numbers, a and b,
-- * if one is zero, return the other number
-- * if not, subtract the smaller number from the larger one
-- * replace the larger number with this new number
-- * repeat
--
-- For example,
-- myGcd 9 12 ==> 3
-- In this case, the algorithm proceeds like this
--
-- a b
--
-- 9 12
-- 9 (12-9)
-- 9 3
-- (9-3) 3
-- 6 3
-- (6-3) 3
-- 3 3
-- (3-3) 3
-- 0 3
--
-- Background reading:
-- * https://en.wikipedia.org/wiki/Euclidean_algorithm※ My solution is at the end of the article.
Haskell: A unique programming paradigm
Functional programming
Haskell is inherently functional. In Haskell, the primary building blocks are functions. Unlike imperative languages, where you write a series of instructions to change the state, Haskell focuses on the application of functions. This paradigm shift brings a unique set of advantages, especially in terms of code clarity and ease of reasoning.
Purity and side-effect free
One of the most compelling aspects of Haskell is its purity. Functions in Haskell do not have side effects, meaning they do not alter any state or interact with the outside world within their execution. This purity ensures that given the same inputs, a function will always return the same output, making Haskell code more predictable and easier to debug.
Laziness
Haskell employs lazy evaluation, meaning that expressions are only evaluated when needed. This allows for the creation of infinite data structures and can lead to performance optimizations by avoiding unnecessary calculations.
Strongly typed with type inference
Haskell’s type system is both strong and expressive. Every value and expression in Haskell has a type, which is checked at compile time, eliminating a whole class of runtime errors. Additionally, Haskell's compiler can infer types, reducing the need for explicit type annotations while maintaining type safety.
Use cases of Haskell
Haskell’s unique features make it suitable for a variety of applications:
- Academic research and education: Haskell's mathematical nature and purity make it an excellent tool for teaching and research in computer science and related fields.
- Financial systems: The predictability and reliability of Haskell’s pure functions make it ideal for financial modeling and quantitative analysis.
- Compilers and interpreters: Haskell’s strong type system and pattern matching capabilities are beneficial in writing compilers and interpreters.
- Concurrent and parallel programming: Haskell’s purity and immutability simplify reasoning about concurrent and parallel programs, reducing the complexity and potential for bugs.
- Web development: While not as mainstream as TypeScript, PHP, Go and such, Haskell has frameworks like Yesod that bring type safety and functional paradigms to web development.
Comparing Haskell with TypeScript and Go
TypeScript
TypeScript, a superset of JavaScript, brings static typing to the dynamic world of JavaScript. While TypeScript improves the reliability and maintainability of JavaScript code, it remains fundamentally imperative and object-oriented, focusing on classes and mutable state.
- Typing: Both TypeScript and Haskell are statically typed, but Haskell’s type system is more expressive and enforced at compile time without the need for extensive annotations.
- Paradigm: TypeScript is multi-paradigm capable of being functional, but it does lean towards imperative and object-oriented programming, while on the other hand Haskell is purely functional.
- Use cases: TypeScript is primarily used for web development, enhancing JavaScript applications. Haskell, while also capable of web development, shines in areas requiring high reliability and mathematical applications.
Go
Go, developed by Google, is designed for simplicity and efficiency in systems programming. It is an imperative language with a focus on concurrency, making it popular for backend services and cloud applications.
- Concurrency: Go has built-in support for concurrent programming with goroutines, making it a strong candidate for networked services. Haskell also supports concurrency, but through a different paradigm using Software Transactional Memory (STM) and lightweight threads.
- Simplicity vs. expressiveness: Go emphasizes simplicity and ease of use, often at the cost of expressiveness. Haskell, on the other hand, provides a rich type system and advanced features, which can be more complex but offer greater power and safety.
- Performance: Go compiles to efficient machine code, similar to Haskell. However, Haskell’s lazy evaluation can sometimes introduce performance overhead, whereas Go’s performance is more predictable.
Conclusion
The Haskell MOOC course has provided a deep understanding of Haskell’s functional programming paradigm, emphasizing its purity, laziness, and strong typing. While Haskell’s approach differs significantly from languages like TypeScript and Go, these differences also highlight its strengths, particularly in areas requiring mathematical precision and reliability. I think by continuing to learn and explore Haskell, it will strengthen my overall skills as a programmer by giving me opportunities to think a bit differently compared to the usual status quo of languages. Also I feel I can utilize the some of the code practices used in Haskell with other languages as well.
Solution
euclideanAlg :: Integer -> Integer -> Integer
euclideanAlg a b
| a == 0 = b
| b == 0 = a
| a > b = euclideanAlg (a - b) b
| otherwise = euclideanAlg a (b - a)
