Function repeat_pattern

repeat_pattern(
    n: number,
    pattern: (a: string) => string,
    initial: string,
): string
Applies a given function n times to an initial value
Parameters
- n: number
  A non-negative integer
- pattern: (a: string) => string
  Unary function from Rune to Rune
- initial: string
  The initial Rune
Returns string
- Result of n times application of pattern to initial: pattern(pattern(...pattern(pattern(initial))...))