Function setInstruction

setInstruction(
    program: Program,
    index: number,
    instruction: Instruction,
): Program
Replaces a single instruction.
Parameters
- program: Program
  Program to edit.
- index: number
  Position to overwrite. Out-of-range indices are ignored.
- instruction: Instruction
  Replacement instruction.
Returns Program
A new program; the input is left untouched.