Compare two equivalent of skip loop function with different paradigm: imperative and functional

micro_bench.n

using System;
using System.Console;
using System.Collections.Generic;
using System.Diagnostics;

def skip_loop(counter, skip, max, idx, lst) {
  if (idx > max) lst 
  else 
    if ( counter >= skip ) 
      skip_loop(1, skip, max, idx + 1, idx :: lst)
    else
      skip_loop(counter + 1, skip, max, idx + 1, lst)    
};


def skippedWhile (skip, max)  {
  mutable res = [];
  mutable i = skip;
  while (i <= max) {
      res ::= i;
      i = i + skip;
  }
  res.Rev()
};


def  maxValue = 1000_000;
def  skipValue = 3;
def  totalRun = 1000;

def benchmark (f) {
  def sw = Stopwatch.StartNew();
  for(mutable i=0; i < totalRun; i++)
      f();
  sw.Stop();
  sw.ElapsedMilliseconds / totalRun    
}

def benchImp = benchmark( () =>  _ = skippedWhile(skipValue, maxValue));
def benchRecu = benchmark( () =>  _ = skip_loop(1, skipValue, maxValue, 1, []).Rev());

WriteLine($"imp = $benchImp\t rec = $benchRecu");
//=> imp = 56         rec = 57

result on next time: imp = 64 rec = 59