5140-trunc.ts

/*
  5140 - Trunc
  -------
  by jiangshan (@jiangshanmeta) #medium #template-literal

  ### Question

  Implement the type version of ```Math.trunc```, which takes string or number and returns the integer part of a number by removing any fractional digits.

  For example:

  ```typescript
  type A = Trunc<12.34> // 12
  ```

  > View on GitHub: https://tsch.js.org/5140
*/

/* _____________ Your Code Here _____________ */

type Pad<T extends number | string> = `${T}` extends `.${infer Rest}` ? `0.${Rest}` : `${T}`;
type Trunc<T extends number | string> = `${Pad<T>}` extends `${infer N}.${infer Rest}` ? N : `${T}`;

/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
    Expect<Equal<Trunc<0.1>, '0'>>,
    Expect<Equal<Trunc<0.2>, '0'>>,
    Expect<Equal<Trunc<1.234>, '1'>>,
    Expect<Equal<Trunc<12.345>, '12'>>,
    Expect<Equal<Trunc<-5.1>, '-5'>>,
    Expect<Equal<Trunc<'.3'>, '0'>>,
    Expect<Equal<Trunc<'1.234'>, '1'>>,
    Expect<Equal<Trunc<'-10.234'>, '-10'>>,
    Expect<Equal<Trunc<10>, '10'>>,
]

/* _____________ Further Steps _____________ */
/*
  > Share your solutions: https://tsch.js.org/5140/answer
  > View solutions: https://tsch.js.org/5140/solutions
  > More Challenges: https://tsch.js.org
*/