Add a floating point type perhaps? (Ducks and runs away)

[binarykitchen]

Hi everyone,

(Awesome library and plenty of pretty unicorns)

There is one TypeScript ... no, more a famous JavaScript/Computer Science related problem haunting me. This classic Binary Representation of Decimals Oracle raised in 1991: https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

We have the type number which can be any number from floats, doubles to integers whatever. I wonder if it's possible to differentiate them within TypeScript? I've run searches and this question hasn't been raised before so I'll give it a try here ...

Because I'm implementing an app doing microtransactions. Picked the mathjs library, which helps. Although I'm still worried about misleading types when it comes to numbers. I don't want to add additional checks in every function whether that number has floating points or not

Thoughts?

[sindresorhus]

We already have that:

type-fest/source/numeric.d.ts

Lines 103 to 124 in cb977aa

	/**
	A `number` that is not an integer.
	Use-case: Validating and documenting parameters.
	It does not accept `Infinity`.
	@example
	```
	import type {Float} from 'type-fest';
	declare function setPercentage<T extends number>(length: Float<T>): void;
	```
	@see Integer
	@category Numeric
	*/
	export type Float<T> =
	T extends unknown // To distributive type
	? IsFloat<T> extends true ? T : never
	: never; // Never happens

[binarykitchen]

Oh man, thanks.

I did run searches before but no results. Perhaps my search query wasn't good enough, or some keywords are missing.

Anyway, I'll give it a try. Keep this ticket open for a couple of days. If there are problems, I will add them here or else, when serious, in separate issues.

🦄

[binarykitchen]

One extra question: are there any other maths libraries out there using your <Float> type?

For example, when I use mathjs floor function, it still returns a number 🤷‍♂️

(Because they all return numbers and I don't want to force type them as this is an anti-pattern)

[benzaria]

@binarykitchen Float<T> is a generic validation type, on its own it doesn't refer to a type and u can't use it like const float: Float = 1.2 it will return never and throw an error