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#include <stdio.h>
// la somme des n premiers entiers
int triangular(int n)
//@ requires n >= 0;
//@ ensures result == n * (n + 1) / 2;
{
int s = 0;
for (int k = 0; k <= n; k++) {
//@ invariant k <= n + 1;
//@ invariant s == (k - 1) * k / 2;
//@ variant n - k;
s += k;
}
return s;
}
int triangular2(int n)
/*@ requires n >= 0;
@ ensures result == n * (n + 1) / 2;
@ variant n; */
{
if (n == 0) return 0;
return n + triangular2(n - 1);
}
int main() {
printf("somme 1 + .. + 100 = %d\n", triangular(100));
printf("somme 1 + .. + 100 = %d\n", triangular2(100));
return 0;
}
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