Very cool that the language allows specification of a type in this way.
I added a similar type — “non-empty-string” to a typechecker for PHP, and it’s been adopted widely in the PHP ecosystem. It turns out to be pretty handy, especially when there’s a full type system to support it.
I've had a Bellroy bag, they're not the most fashionable but super high quality and well thought-out. Just like Haskell code—maybe that's why they like it.
In the backpack community bellroy is often seen as “meh”. Eg. they frequently don’t live up to the guarantees they give and to the quality they promise. Also overpriced.
This example is not only wrong for what you intend to demonstrate but even if it wasn't, it's not problematic. In typescript the proper way to do this is using branded types and exporting only the safe constructor, making anyone who wants to violate the invariant go out of their way, which is no different from the situation in any number of programming languages or scenarios.
declare const brand: unique symbol;
type NonEmptyString = string & { readonly [brand]: 'NonEmptyString' };
// the ONLY non-cast way to produce one
export function nonEmptyString(s: string): NonEmptyString | undefined {
return s.length > 0 ? (s as NonEmptyString) : undefined;
}
export type { NonEmptyString };
Very cool that the language allows specification of a type in this way.
I added a similar type — “non-empty-string” to a typechecker for PHP, and it’s been adopted widely in the PHP ecosystem. It turns out to be pretty handy, especially when there’s a full type system to support it.
"Huh never heard of Bellroy... I wonder what they're using Haskell for..."
Turns out it's some kind of bags and accessories brand!
I've had a Bellroy bag, they're not the most fashionable but super high quality and well thought-out. Just like Haskell code—maybe that's why they like it.
In the backpack community bellroy is often seen as “meh”. Eg. they frequently don’t live up to the guarantees they give and to the quality they promise. Also overpriced.
I pondered for a while, it IS the company I used to know
I once saw a job ad for a company selling a horoscope app that required Haskell. An unusual conjunction for sure.
Astrology and Haskell are quite similar in that both are much much easier to do if you have a math degree.
Using Haskell for a horoscope app is like hiring a mathematician to read tea leaves
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Language is not mentioned in a title, so my first thought was about TypeScript type wizardry. Turns out it's as simple as `Exclude<string, "">`.
https://www.typescriptlang.org/docs/handbook/utility-types.h...
Edit: nevermind, LLM fooled me.
It's simple, and it doesn't work as `Exclude` only applies to union types. For type `string` it just returns the same type `string`.
yup, it's not possible to do it safely with a simple unparameterised type: https://www.typescriptlang.org/play/?#code/C4TwDgpgBAcg9gOwK...
It is very much mentioned in the article title and the first sentence. It's just HN that's truncated the title.
Speaking of TS, there's stuff in there for typing strings / string formats: https://www.typescriptlang.org/docs/handbook/2/template-lite...
Daily reminder that TypeScript's type checker is not sound.
https://www.typescriptlang.org/play/?#code/C4TwDgpgBAcg9gOwK...
This example is not only wrong for what you intend to demonstrate but even if it wasn't, it's not problematic. In typescript the proper way to do this is using branded types and exporting only the safe constructor, making anyone who wants to violate the invariant go out of their way, which is no different from the situation in any number of programming languages or scenarios.
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