When comparing Nim vs Reason ML, the Slant community recommends Nim for most people. In the question“What are the best languages that compile to JavaScript? ” Nim is ranked 3rd while Reason ML is ranked 10th. The most important reason people chose Nim is:
There are generics, templates, macros in Nim. They can allow you to write new DSL for your application, or avoid all boilerplate stuff.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Great metaprogramming features
There are generics, templates, macros in Nim. They can allow you to write new DSL for your application, or avoid all boilerplate stuff.
Pro Strict typing
Checks your code at compile time.
Pro Has built-in unittest module
With built-in "unittest" module you can create test with a very readable code.
Pro Has built-in async support
Nim has "asyncdispatch" module, which allows you to write async applications.
Pro Compile-time execution
Nim has a built-in VM, which executes macros and some other code at compile time. For example, you can check if you're on Windows, and Nim will generate code only for it.
Pro Really cross-platform
The same code can be used for web, server, desktop and mobile.
Pro Easy to read
Nim has a lot of common with Python in terms of syntax. Indentation-based syntax, for/while loops.
Pro Multi paradigm
Imperative, OOP, functional programming in one language.
Pro Easy to integrate with another languages
You can use Nim with any language that can be interfaced with C. There's a tool which helps you to create new C and C++ bindings for Nim - c2nim.
Also, you can use Nim with Objective C or even JavaScript (if you're compiling for these backends).
Pro Garbage-collected
You don't need to deal with all those manual memory allocations, Nim can take care of it. But also you can use another GC, or tweak it for your real-time application or a game.
Pro Type interferencing
You only need to specify types in your procedures and objects - you don't need to specify type when you're creating a new variable (unless you're creating it without initialization).
Pro Built-in Unicode support
You can use unicode names for variables, there is "unicode" module for operations with unicode.
Pro Supports UFCS (Unified Function Call Syntax)
writeLine(stdout, "hello") can be written as stdout.writeLine("hello")
proc add(a: int): int = a + 5 can be used like 6.add.echo or 6.add().echo()
Pro Uses the excellent Bucklescript Ocaml to Javascript transpiler
Pro Superior type inference
Ocaml type inference is so smart that you never have to repeat yourself and keep code very clean, type errors also are very pleasant.
Pro Aims to make the transition from Javascript easier
Despite being a completely different language Javascript programmer will find that the syntax of ReasonML has many familiarities with Javascript.
Pro Uses established compiler technology from Ocaml with a tweaked syntax that leans more towards Javascript
Pro Removes JavaScript "bad parts" but sticks to it's design philosophy
unlike other js-targetting languages that are thought as a way to have a language that pleases community X run in a browser, reason is really designed with JavaScript community in mind. it removes the bad parts but keeps its syntax and its best design principles (from Scheme): simplicity, minimalism, and functions as building block.
Pro Immutability with escape hatches
reason includes true immutability, but it has escape hatches to let you use mutations in exceptional cases.
Pro Compiles to JavaScript or assembly (ocaml)
The same reasonml code can compile to js (eg. run on browsers or node.js, use any lib in npm), or compile to assembly thru ocaml (unless of course you load js externals), running on any device, with C-comparable (or better) performance.
Pro JSX syntax natively supported
Reason was created by the creator of react, for developers already using JSX to template web or native UIs this results very familiar.
Cons
Con A standard async syntax is pending
Async syntax is not standard across native/js projects and in both cases a bit awkward for non-ocaml devs. Currently this is reasonml most voted issue in their GitHub repo so hopefully, there's news soon.
Con Ecosystem is a mess
A wonderful language, but a user is required to use multiple different package managers for many things (esy, bsb, npm). Some standard templates from bsb (e.g. react-starter) are not installable out of the box.
