Use foreach instead of while with l_nth

[filipeom]

The while with l_nth pattern is often used in the interpreter.

However, in my experimental evaluation:

function main() {
  // List with 10000 integer elements
  lst := [0, 1, ..., 9999]
  n := l_len(lst);
  i := 0;
  while (i < n) {
    v := l_nth(lst, i);
    print v;
    i := i + 1;
  }
  return 0;
}

function main() {
  // List with 10000 integer elements
  lst := [0, 1, ..., 9999]
  res := 0;
  foreach (v : lst) {
    res := res + v;
  }
  return 0;
}

is:

hyperfine "ecma-sl interpret while.esl" "ecma-sl interpret foreach.esl"
Benchmark 1: ecma-sl interpret while.esl
  Time (mean ± σ):     126.3 ms ±   3.4 ms    [User: 113.0 ms, System: 13.3 ms]
  Range (min … max):   121.3 ms … 134.6 ms    23 runs

Benchmark 2: ecma-sl interpret foreach.esl
  Time (mean ± σ):      47.9 ms ±   2.2 ms    [User: 34.9 ms, System: 12.9 ms]
  Range (min … max):    45.6 ms …  57.3 ms    64 runs

Summary
  ecma-sl interpret foreach.esl ran
    2.64 ± 0.14 times faster than ecma-sl interpret while.esl

• 2.64 faster