[Lib] int.rs, uint.rs: added max_value, min_value

Author: David Rajchenbach-Teller

src/lib/int.rs

@@ -1,3 +1,10 @@
+fn max_value() -> int {
+  ret min_value() - 1;
+}
+
+fn min_value() -> int {
+  ret (-1 << (sys::size_of::<int>()  * 8u as int - 1)) as int;
+}
 
 
 pure fn add(x: int, y: int) -> int { ret x + y; }

src/lib/uint.rs

@@ -1,5 +1,19 @@
+/**
+ * Return the minimal value for an uint.
+ *
+ * This is always 0
+ */
 pure fn min_value() -> uint { ret 0u; }
 
+/**
+ * Return the maximal value for an uint.
+ *
+ * This is 2^wordsize - 1
+ */
+pure fn max_value() -> uint {
+     ret 0u - 1u;
+}
+
 fn add(x: uint, y: uint) -> uint { ret x + y; }
 
 fn sub(x: uint, y: uint) -> uint { ret x - y; }

src/test/stdtest/int.rs

@@ -23,3 +23,10 @@ fn test_pow() {
     assert (int::pow(-3, 3u) == -27);
     assert (int::pow(4, 9u) == 262144);
 }
+
+#[test]
+fn test_overflows() {
+   assert (int::max_value() > 0);
+   assert (int::min_value() <= 0);
+   assert (int::min_value() + int::max_value() + 1 == 0);
+}

src/test/stdtest/uint.rs

@@ -47,3 +47,10 @@ fn test_next_power_of_two() {
     assert (uint::next_power_of_two(38u) == 64u);
     assert (uint::next_power_of_two(39u) == 64u);
 }
+
+#[test]
+fn test_overflows() {
+   assert (uint::max_value() > 0u);
+   assert (uint::min_value() <= 0u);
+   assert (uint::min_value() + uint::max_value() + 1u == 0u);
+}