When comparing Earl Grey vs Idris, the Slant community recommends Idris for most people. In the question“What are the best languages that compile to JavaScript? ” Idris is ranked 23rd while Earl Grey is ranked 29th. The most important reason people chose Idris is:
Idris not only has support for type classes, but is a fully dependently typed language, giving you the full power to statically verify your code.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Powerful hygienic macros
Earl Grey's macro system allows for creating powerful control structures that look just like builtin ones. EG also supports macro libraries which allows developers to provide their macros/DSLs for others to use.
Pro Pattern matching
Pattern matching is an incredibly powerful tool that, once you've tried, you cannot live without. This is not your average hacked-together pattern matching but a complete and integral feature to the language.
Pro ECMAScript 6 Asynchrony
Earl Grey provides Promises based on ECMAScript version 6 and as many NPM libraries already implement. Earl Grey also provides a promisify
function that converts old-fashioned callback-style asynchrony to promises.
Pro Fully compatible with Node.js ecosystem
Anything available on NPM can be used just as easily with Earl Grey. In fact, everything else can be used too! Earl Grey has interfaces to Browserify, Webpack, and even experimental support for SystemJS. Earl Grey can even be used to generate npm packages that any node-compatible language can use!
Pro Full dependent types
Idris not only has support for type classes, but is a fully dependently typed language, giving you the full power to statically verify your code.
Pro Domain driven design and type driven development
Because of full dependent types in Idris, the programmer can focus more on modelling the domain with types and waste less time fixing common bugs that the type checker will catch. Dependent types help apply type driven development and a lot of code auto generation, making the compiler and type checker an ally in developing working software instead of just getting in the way.
Cons
Con Not true static typing
EG gives you the tools to implement your own type-checking inside of argument lists and elsewhere but there's no analysis done at compile-time like other compile-to-js languages.
Con Unfamiliar syntax
While the language shares a lot of DNA with Python, there are still many new (and interesting) features/sugar that may take some time to get used to.
Con Not widely used
Con Not widely used
Con Weaker type inference
As type inference is undecidable for dependently-typed languages, Idris cannot offer the full type inference that Haskell supports, and so more type annotations will be needed.
Con Different semantics from Haskell
Idris, while similar to Haskell, has strict semantics, which may cause some confusion if your backend is done in Haskell. If using Idris, it would make sense to do the backend in Idris as well, if not for the fact that Idris currently has fewer libraries available for web development than Haskell.