# Reasons that people were forced to move from Elm to something else?

**URL:** <https://discourse.elm-lang.org/t/reasons-that-people-were-forced-to-move-from-elm-to-something-else/6390>\
**Category:** Learn\
**Created:** [October 11, 2020, 2:02pm UTC](https://discourse.elm-lang.org/t/reasons-that-people-were-forced-to-move-from-elm-to-something-else/6390 "2020-10-11T14:02:51Z")\
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**Author:** ![solificati](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@solificati](https://discourse.elm-lang.org/u/solificati)\
**Post date:** [October 15, 2020, 3:05pm UTC](https://discourse.elm-lang.org/t/reasons-that-people-were-forced-to-move-from-elm-to-something-else/6390/17 "2020-10-15T15:05:06Z")

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> [@rupert](#):
>
> Its been a while since I used OCaml (20 years), what does Reason have modelling wise over Elm? Is the extensible union types? Or the module system perhaps?

GADTs and polymorphic variants open a lot of possibilities for us. Also module system is more powerful (really, modules are different thing in OCaml and name is rather poor).

We use GADTs to express flows as data structures and interpreters for them.

Module system helps with parsers and writing isomorphisms for schemas (functions that convert between complex data structures) - we can extend more basic types with implementations so bigger isos/parsers compose better.

Polymorphic variants are mote like a nice tool here and there - they change nothing in big way, but are quite useful for pseudo row types. This is more like stylistic choice and to be honest, we find Elm extensible records good fit for the same use cases.

Also, please note that our recommendations are taking into consideration multiple factors. We chose Reason not only because of “more powerful” type system but also due to genType, interoperability, community and tooling. It is just a result of specific needs.

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