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Recently learned about Gleam and am very interested in it as someone who always wanted to like Elixir but dislikes the Ruby syntax and lack of static typing. Lo
by dcre 3y ago
Recently learned about Gleam and am very interested in it as someone who always wanted to like Elixir but dislikes the Ruby syntax and lack of static typing. Love this approach to demonstrating the language in context.
As a mostly frontend dev I feel it’s worth mentioning that while it’s a nice way to try Gleam, the Gleam aspect of this is inessential, TypeScript is quite good, and using create-tauri-app with the react-ts, vue-ts, or svelte-ts preset is also a great way to try making cross-platform GUIs with Tauri. It uses Vite under the hood, and the generated app is extremely minimal — nothing like the awful create-react-app behemoths that probably left a bad taste in everyone’s mouth.
- weatherlight 3y agoGleam's type system is just a Hindley-Milner type system. Which is tried, true and simpler, and extensively battle tested. Typescript's type system isn't sound. Gleam's is.
- wezm 3y ago> the Gleam aspect of this is inessential, TypeScript is quite good TypeScript can be quite productive but I find its type system lacking. Specifically the use of structural typing/lack of nominal typing and lack of sum types. I find these extremely useful when writing reliable software, which is why Gleam appeals to me.
- Tade0 3y agoThat's by all design. Does this prevent you from writing reliable software?
- dcre 3y agoIt has sum types! Type unions with a discriminator.
- wezm 3y agoIt kinda does if https://www.typescriptlang.org/play#example/discriminate-types https://www.typescriptlang.org/play#example/discriminate-typ... is what you're referring to but it appears to be missing one of the major benefits: an error/warning if you haven't handled all variants. Edit: lots of replies showing how TypeScript can be made to do exhaustiveness checking. It's neat and all but it's a lot of gymnastics compared to languages that just have this built in, which again is part of the appeal of Gleam for me.
- superice 3y agoOh that’s easy to fake with type narrowing: function expectType<A, B extends A>() {} expectType<never, typeof yourUnion>(); The function call will fail at compile time if yourUnion is anything more than never, which you can use in your else case of if statements that narrow the discriminated union.
- dcre 3y agoYeah, that can be annoying. Until pattern matching makes it into JS, the main way people deal with this is to use a library. For example, ts-pattern lets you stick `.exhaustive()` at the end of a match call and I believe you get the error at typechecking time, not runtime. https://github.com/gvergnaud/ts-pattern https://github.com/gvergnaud/ts-pattern
- smj-edison 3y agoI ran into this exact issue when I was working on a piece of typescript that interoperates with a rust server, here's how I was able to do exhaustiveness checking (the errors aren't the prettiest, but it works): https://github.com/wwtos/mjuo/blob/main/vpo-frontend/src/lib/util/discriminated-union.ts https://github.com/wwtos/mjuo/blob/main/vpo-frontend/src/lib... EDIT: and an example of usage: https://github.com/wwtos/mjuo/blob/ca8c514185c1b5bb22aec752a4c41da0a50dcd4d/vpo-frontend/src/routes/node_editor/Node.svelte#L58 https://github.com/wwtos/mjuo/blob/ca8c514185c1b5bb22aec752a...
- laurencerowe 3y agoYou can workaround the lack of exhaustive matching with the following pattern: type Variant = { kind: "value", value: string } | { kind: "error", error: string } | { kind: "unexpected" }; class Unreachable extends Error { constructor(unexpected: never) { super(`${unexpected}`); } } function useVariant(variant: Variant) { switch (variant.kind) { case "value": return variant.value; case "error": return variant.error; default: throw new Unreachable(variant); } } The `new Unreachable(variant)` will fail the type check only when you have not exhaustively matched all variants.