ocaml VS melange

Compare ocaml vs melange and see what are their differences.


The core OCaml system: compilers, runtime system, base libraries (by ocaml)


A mixture of tooling combined to produce JavaScript from OCaml & Reason (by melange-re)
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ocaml melange
116 14
5,088 730
1.0% 2.7%
9.8 9.6
about 6 hours ago 4 days ago
OCaml OCaml
GNU General Public License v3.0 or later GNU General Public License v3.0 or later
The number of mentions indicates the total number of mentions that we've tracked plus the number of user suggested alternatives.
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.


Posts with mentions or reviews of ocaml. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2023-11-12.
  • OCaml: a Rust developer's first impressions
    4 projects | news.ycombinator.com | 12 Nov 2023
    > But .mli files do not help with the "no types in the source code" problém

    It partially helps since it forces you to have types where they matters most: interfaces.

    > And I did not experience any advantage of separate signature files so far,

    100kLoc is already quite big! I'm starting to think I'm an outlier since a lot of people don't see the benefits :)

    For me, it helps because I really don't want to see the implementation when I use an API. If I need to look at the implementation, it means the interface isn't well specified. All I need should be in the interface: types, docs, (abstract) types. And no more.

    Typically, an .ml file will have more than what is exported, types won't be abstract but will have a concrete implementation, and type signatures may be missing. How would it feels like to use list if only https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.ml was available, instead of https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.mli?

    Haskell tells you what is exported from a module, but it only shows you the names. To see the signatures, you need to rely on generated doc.

    Arguably, since OCaml has includes, it suffers from the same problem, your ".mli" may have tons of include and it becomes harder to see what's exported without an external tool

    4 projects | news.ycombinator.com | 12 Nov 2023
    > It partially helps since it forces you to have types where they matters most: exported functions

    But the problém the OP has is not knowing the types when reading the source (in the .ml file).

    > How would it feels like to use list if only https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.ml was available,

    If the signature where in the source file (which you can do in OCaml too), there would be no problem - which is what all the other (for some definition of "other") languages except C and C++ (even Fortran) do.

    No, really, I can't see a single advantage of separate .mli files at all. The real problém is that the documentation is often worse too, as the .mli is autogenerated and documented afterwards - and now changes made later in the sources need to be documented in the mli too, so anything that doesn't change the type often gets lost. The same happens in C and C++ with header files.

  • Bringing more sweetness to ruby with sorbet types 🍦
    5 projects | dev.to | 18 Sep 2023
    If you have been in the Ruby community for the past couple of years, it's possible that you're not a super fan of types or that this concept never passed through your mind, and that's totally cool. I myself love the dynamic and meta-programming nature of Ruby, and honestly, by the time of this article's writing, we aren't on the level of OCaml for type checking and inference, but still, there are a couple of nice things that types with sorbet bring to the table:
  • What is gained and lost with 63-bit integers? (2014)
    2 projects | news.ycombinator.com | 12 Aug 2023
    Looks like there have been proposals to eliminate use of 3 operand lea in OCaml code (not accepted sadly):


  • What can Category Theory do?
    2 projects | /r/askmath | 22 Jun 2023
    Haskell and Agda are probably the most obvious examples. Ocaml too, but it is much older, so its type system is not as categorical. There is also Idris, which is not as well-known but is very cool.
  • Playing Atari Games in OCaml
    2 projects | news.ycombinator.com | 15 Jun 2023
  • Bloat
    4 projects | /r/ProgrammingLanguages | 22 May 2023
    That does sound problematic, but without the code it is hard to tell what is the issue. Typically, compiling a 6kLoc file like https://github.com/ocaml/ocaml/blob/trunk/typing/typecore.ml takes 0.8 s on my machine.
    4 projects | /r/ProgrammingLanguages | 22 May 2023
  • Key takeways from OpenAI CEO's 3-hour Senate testimony, where he called for AI models to be licensed by US govt. Full breakdown inside.
    2 projects | /r/ChatGPT | 17 May 2023
    NEAT is a fascinating algorithm. I've been interested in it ever since SethBling made a video about it playing Mario and this series of experiments about a variant of NEAT that evolves in real-time rather than by-generation. I'm finally getting to be just good enough of a programmer that I am actually considering writing my own (probably in OCaml because there's an unfortunate lack of NEAT implementations in functional programming languages).
  • So Hows the Hackathon Going?
    4 projects | /r/ProgrammerHumor | 10 May 2023
    easier than haskell and easier for writing compilers: https://ocaml.org/


Posts with mentions or reviews of melange. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2024-02-27.
  • Melange for React devs book, alpha release
    2 projects | news.ycombinator.com | 27 Feb 2024
    Hey HN, at Ahrefs we have been working on an online book that hopefully helps React developers get up and running with Melange, an OCaml to JavaScript compiler. You can read more about Melange here: https://melange.re/.

    There are still a few chapters that we'd like to add before considering it "complete", but it might be already helpful for some folks out there, that's why we decided to publish it early.

    The book uses Reason syntax to implement React components using ReasonReact components. You can read more about both in:


  • Reason and React Meta-Frameworks
    5 projects | dev.to | 17 Oct 2023
    In my previous post on trying to use the NextJS App Router and Reason I described some of the problems and limitations of their compatibility with one another. With the release of Melange 2 I decided to see if the new features of Melange 2 could help to increase the compatibility of Reason and the NextJS App Router. I have also documented some of the things learnt after trying Melange (v1) with Astro and Remix.
  • OCaml 5.0 Alpha Release
    5 projects | news.ycombinator.com | 15 Jun 2022
    So it's Reason, not ReasonML which the umbrella project's name, and Rescript is a imcompatible syntax split from the Bucklescript team (that previously transpiled Reason to JS). Bucklescript's new name is... Rescript.

    But not everyone agrees with the split and work is being done on Melange to replace Bucklescript : https://github.com/melange-re/melange

    Ultimately JsOfOcaml can directly transpile Ocaml to JS.

  • Question about the Reason project in general
    3 projects | /r/rescript | 4 Feb 2022
    In reality, most folks that developed BuckleScript frontends with ReasonML switched to ReScript syntax and are happy with it. Some felt more friction because of their reliance on PPXes or FP-heavy libraries (like Relude) and those people tend to use the Melange fork of BuckleScript or they switched to js_of_ocaml.
  • From TypeScript to ReScript
    12 projects | news.ycombinator.com | 12 Jan 2022
    There is a fork of ReScript that supports ReasonML syntax and with the goal of maintaining Ocaml compatibility: https://github.com/melange-re/melange.
  • Are Dynamic Languages Going to Replace Static Languages? (2003)
    7 projects | news.ycombinator.com | 4 Aug 2021
  • Writing custom VSCode extensions in ReasonML
    2 projects | /r/reasonml | 21 Jul 2021
    For OCaml and ReasonML your options are js_of_ocaml (mentioned here in ReasonML docs) or a fairly new fork of BuckleScript called melange. They differ in implementation and output, with JSOO taking intermediate bytecode generated by ocamlc and turning it into unreadable JS, vs Melange being a patched compiler that builds more human-readable JS.
  • Using `let.opt` in Rescript with latest Reason/OCaml
    3 projects | dev.to | 11 Jul 2021
  • Is there a statically typed functional programming language that doesn't take purity so seriously?
    7 projects | /r/functionalprogramming | 1 Jun 2021
    TL;DR: Reason is, and always has been, independent of ReScript (formerly BuckleScript) and is still actively maintained. If you want to use Reason or OCaml to make native code you can. If you want to compile JS from OCaml or Reason you also still can, but you'll want to use either js_of_ocaml or a BuckleScript fork named Melange that was made in response to the BuckleScript/ReScript people's shenanigans. And if you only care about JS-like syntax and JS output, you can use ReScript.
  • JavaScript file watching with Reason & Rescript in Dune
    5 projects | dev.to | 12 May 2021
    While banging my head against the wall trying to understand the Dune build system used with OCaml and the Melange project I came across these great simple videos by @TheEduardoRFS.

What are some alternatives?

When comparing ocaml and melange you can also consider the following projects:

js_of_ocaml - Compiler from OCaml to Javascript.

Alpaca-API - The Alpaca API is a developer interface for trading operations and market data reception through the Alpaca platform.

rescript-compiler - The compiler for ReScript.

VisualFSharp - The F# compiler, F# core library, F# language service, and F# tooling integration for Visual Studio

dune - A composable build system for OCaml.

reason - Simple, fast & type safe code that leverages the JavaScript & OCaml ecosystems

TradeAlgo - Stock trading algorithm written in Python for TD Ameritrade.

rust - Rust for the xtensa architecture. Built in targets for the ESP32 and ESP8266

rust - Empowering everyone to build reliable and efficient software.

koka - Koka language compiler and interpreter

Nim - Nim is a statically typed compiled systems programming language. It combines successful concepts from mature languages like Python, Ada and Modula. Its design focuses on efficiency, expressiveness, and elegance (in that order of priority).