range.ts

range.ts

export function range(length: number): IterableIterator<number>
export function range(start: number, stop: number): IterableIterator<number>
export function range(start: number, stop: number, step: number): IterableIterator<number>
export function* range(start: number, stop?: number, step = 1): IterableIterator<number> {
  if (stop === undefined) {
    return yield* range(0, start)
  }

  if (step === 0) {
    throw new RangeError('Step cannot be zero.')
  }

  if ((start < stop && step < 0) || (start > stop && step > 0)) {
    throw new RangeError('Sign of step value causes infinite range.')
  }

  if (step > 0) {
    for (let i = start; i < stop; i += step) {
      yield i  
    }
  }
  else {
    for (let i = start; i > stop; i += step) {
      yield i
    }
  }
}