Associativity math: (a + b) + c != a + (b + c)

Question

Recently I was going through an old blog post by Eric Lippert in which, while writing about associativity he mentions that in C#, (a + b) + c is not equivalent

Answer 1

A couple of similar examples:

static void A(string s, int i, int j)
{
  var test1 = (s + i) + j;
  var test2 = s + (i + j);
  var testX = s + i + j;
}

Here A("Hello", 3, 5) leads to test1 and testX being equal to "Hello35", while test2 will be "Hello8".

And:

static void B(int i, int j, long k)
{
  var test1 = (i + j) + k;
  var test2 = i + (j + k);
  var testX = i + j + k;
}

Here B(2000000000, 2000000000, 42L) leads to test1 and testX being equal to -294967254L in usual unchecked mode, while test2 becomes 4000000042L.