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less-than.d.ts
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60 lines (44 loc) · 1.15 KB
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import type {GreaterThanOrEqual} from './greater-than-or-equal.d.ts';
/**
Returns a boolean for whether a given number is less than another number.
@example
```
import type {LessThan} from 'type-fest';
type A = LessThan<1, -5>;
//=> false
type B = LessThan<1, 1>;
//=> false
type C = LessThan<1, 5>;
//=> true
```
Note: If either argument is the non-literal `number` type, the result is `boolean`.
@example
```
import type {LessThan} from 'type-fest';
type A = LessThan<number, 1>;
//=> boolean
type B = LessThan<1, number>;
//=> boolean
type C = LessThan<number, number>;
//=> boolean
```
@example
```
import type {LessThan} from 'type-fest';
// Use `LessThan` to constrain a function parameter to negative numbers.
declare function setNegative<N extends number>(value: LessThan<N, 0> extends true ? N : never): void;
setNegative(-1); // ✅ Allowed
setNegative(-2); // ✅ Allowed
// @ts-expect-error
setNegative(0);
// @ts-expect-error
setNegative(1);
```
*/
export type LessThan<A extends number, B extends number> =
GreaterThanOrEqual<A, B> extends infer Result
? Result extends true
? false
: true
: never; // Should never happen
export {};