source: CIVL/mods/dev.civl.com/examples/loop_invariants/dev/max.cvl@ cb4d4f4

#include <assert.h>

#pragma CIVL ACSL

$input int N;
$assume(N > 0);     
$input double a[N];

int main() {
  int i = 0;
  double max = a[0];
  
  /*@ loop invariant 1 <= i && i <= N;
    @ loop invariant \forall int t; 0 <= t && t < i ==> a[t] <= max;
    @ loop invariant \exists int t; 0 <= t && t < i ==> a[t] == max;
    @ loop assigns i, max;
    @*/
  for (i = 1; i < N; i++)
    if (a[i] > max)
      max = a[i];

  assert($forall (int i : 0 .. N-1) a[i] <= max);
  assert($exists (int i : 0 .. N-1) a[i] == max);
}