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Elm vs Haskell: What are the differences?


Elm and Haskell are both functional programming languages that have gained popularity in recent years. While they share many similarities, there are also key differences between the two.

1. Type Inference One major difference between Elm and Haskell is their approach to type inference. In Elm, the type inference is automatic and the language is designed to be beginner-friendly. On the other hand, Haskell has a more powerful and advanced type system that allows for more fine-grained control and explicit type annotations.

2. Mutable State Another significant difference between Elm and Haskell is their treatment of mutable state. Elm emphasizes immutability and enforces strict functional purity, where all values are immutable by default. In contrast, Haskell allows mutable state through the use of monads and the IO (input/output) system.

3. Handling Effects Elm and Haskell also differ in how they handle side effects and IO operations. Elm uses a declarative approach called "The Elm Architecture" to manage the effects, making it easier to reason about the code and prevent runtime errors. Haskell, on the other hand, uses a monadic approach with the IO type to handle effects, providing more flexibility at the cost of additional complexity.

4. Ecosystem and Community The ecosystems and communities surrounding Elm and Haskell also differ. Elm has a smaller and more focused ecosystem, with a primary focus on web development and a limited number of packages available. Haskell, on the other hand, has a larger and more mature ecosystem with a wide range of libraries and frameworks available for different use cases.

5. Performance In terms of performance, Haskell generally outperforms Elm due to its more optimized compiler and more advanced runtime system. Elm, on the other hand, prioritizes simplicity and ease of use over performance optimizations, which makes it more suitable for smaller web applications or prototypes.

6. Learning Curve Finally, the learning curves for Elm and Haskell differ. Elm is designed to be beginner-friendly and has a gentle learning curve, making it easier for newcomers to get started with functional programming. Haskell, on the other hand, has a steeper learning curve due to its advanced type system and more complex concepts, making it more suitable for experienced programmers.

In summary, Elm and Haskell differ in their approach to type inference, handling of mutable state, management of effects, ecosystem and community, performance, and learning curve. Elm prioritizes simplicity and beginner-friendliness, while Haskell offers more advanced features and flexibility at the cost of increased complexity.

Decisions about Elm and Haskell
Timm Stelzer
VP Of Engineering at Flexperto GmbH · | 18 upvotes · 613.6K views

We have a lot of experience in JavaScript, writing our services in NodeJS allows developers to transition to the back end without any friction, without having to learn a new language. There is also the option to write services in TypeScript, which adds an expressive type layer. The semi-shared ecosystem between front and back end is nice as well, though specifically NodeJS libraries sometimes suffer in quality, compared to other major languages.

As for why we didn't pick the other languages, most of it comes down to "personal preference" and historically grown code bases, but let's do some post-hoc deduction:

Go is a practical choice, reasonably easy to learn, but until we find performance issues with our NodeJS stack, there is simply no reason to switch. The benefits of using NodeJS so far outweigh those of picking Go. This might change in the future.

PHP is a language we're still using in big parts of our system, and are still sometimes writing new code in. Modern PHP has fixed some of its issues, and probably has the fastest development cycle time, but it suffers around modelling complex asynchronous tasks, and (on a personal note) lack of support for writing in a functional style.

We don't use Python, Elixir or Ruby, mostly because of personal preference and for historic reasons.

Rust, though I personally love and use it in my projects, would require us to specifically hire for that, as the learning curve is quite steep. Its web ecosystem is OK by now (see, but in my opinion, it is still no where near that of the other web languages. In other words, we are not willing to pay the price for playing this innovation card.

Haskell, as with Rust, I personally adore, but is simply too esoteric for us. There are problem domains where it shines, ours is not one of them.

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Pros of Elm
Pros of Haskell
  • 45
    Code stays clean
  • 44
    Great type system
  • 40
    No Runtime Exceptions
  • 33
  • 28
    Easy to understand
  • 23
    Type safety
  • 22
  • 17
    JS fatigue
  • 12
    Ecosystem agrees on one Application Architecture
  • 12
  • 10
    Friendly compiler messages
  • 8
    Fast rendering
  • 7
    If it compiles, it runs
  • 7
    Welcoming community
  • 5
    Stable ecosystem
  • 4
    'Batteries included'
  • 2
  • 90
    Purely-functional programming
  • 66
    Statically typed
  • 59
  • 39
    Open source
  • 38
    Great community
  • 31
    Built-in concurrency
  • 30
    Built-in parallelism
  • 30
  • 24
    Referentially transparent
  • 20
  • 15
    Type inference
  • 15
    Intellectual satisfaction
  • 12
    If it compiles, it's correct
  • 8
  • 8
  • 5
    Great type system
  • 4
    Proposition testing with QuickCheck
  • 4
    One of the most powerful languages *(see blub paradox)*
  • 4
    Purely-functional Programming
  • 3
    Highly expressive, type-safe, fast development time
  • 3
    Pattern matching and completeness checking
  • 3
    Great maintainability of the code
  • 3
  • 3
  • 2
    Best in class thinking tool
  • 2
    Kind system
  • 2
    Better type-safe than sorry
  • 2
    Type classes
  • 1
  • 1

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Cons of Elm
Cons of Haskell
  • 3
    No typeclasses -> repitition (i.e. map has 130versions)
  • 2
    JS interop can not be async
  • 2
    JS interoperability a bit more involved
  • 1
    More code is required
  • 1
    No JSX/Template
  • 1
    Main developer enforces "the correct" style hard
  • 1
    No communication with users
  • 1
    Backwards compability breaks between releases
  • 9
    Too much distraction in language extensions
  • 8
    Error messages can be very confusing
  • 5
    Libraries have poor documentation
  • 3
    No good ABI
  • 3
    No best practices
  • 2
    Poor packaging for apps written in it for Linux distros
  • 2
    Sometimes performance is unpredictable
  • 1
    Slow compilation
  • 1
    Monads are hard to understand

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What companies use Elm?
What companies use Haskell?
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What are some alternatives to Elm and Haskell?
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It lets you write simple, fast and quality type safe code while leveraging both the JavaScript & OCaml ecosystems.It is powerful, safe type inference means you rarely have to annotate types, but everything gets checked for you.
If you've ever built a JavaScript application, the chances are you've encountered – or at least heard of – frameworks like React, Angular, Vue and Ractive. Like Svelte, these tools all share a goal of making it easy to build slick interactive user interfaces. Rather than interpreting your application code at run time, your app is converted into ideal JavaScript at build time. That means you don't pay the performance cost of the framework's abstractions, or incur a penalty when your app first loads.
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