Edge case in is_square

Author: SuprDewd

code/tricks/is_square.cpp

@@ -2,6 +2,7 @@ long long M;
 void init_is_square() {
   rep(i,0,64) M |= 1ULL << (63-(i*i)%64); }
 inline bool is_square(ll x) {
+  if (x == 0) return true; // XXX
   if ((M << x) >= 0) return false;
   int c = __builtin_ctz(x);
   if (c & 1) return false;

code/tricks/is_square.test.cpp

@@ -1,12 +1,18 @@
 void test() {
   init_is_square();
 
+  assert_true(is_square(0));
+  assert_true(is_square(1));
+  assert_false(is_square(2));
+  assert_false(is_square(3));
+  assert_true(is_square(4));
+
   rep(i,0,100000) {
     int n = rand() % 100000000;
     int st = sqrt(n);
     while (st*st > n) st--;
     while (st*st < n) st++;
-    assert_equal(st*st == n, is_square(n));
+    assert_equal(st*st == n, is_square(n), true);
   }
 }
 // vim: cc=60 ts=2 sts=2 sw=2: