Merge rust-num#210

210: Add LowerBounded/UpperBounded traits r=cuviper a=clarfonthey

Potential solution for rust-num#208. With a breaking change, these could simply become supertraits of `Bounded`, but until then, we have to deal with blanket implementations.

I added both simply because it was easy to do so, although we could opt to not require both. I don't see it being that negative to include both, however.

Co-authored-by: ltdk <[email protected]>

src/bounds.rs

@@ -8,12 +8,38 @@ use core::{u16, u32, u64, u8, usize};
 /// Numbers which have upper and lower bounds
 pub trait Bounded {
     // FIXME (#5527): These should be associated constants
-    /// returns the smallest finite number this type can represent
+    /// Returns the smallest finite number this type can represent
     fn min_value() -> Self;
-    /// returns the largest finite number this type can represent
+    /// Returns the largest finite number this type can represent
     fn max_value() -> Self;
 }
 
+/// Numbers which have lower bounds
+pub trait LowerBounded {
+    /// Returns the smallest finite number this type can represent
+    fn min_value() -> Self;
+}
+
+// FIXME: With a major version bump, this should be a supertrait instead
+impl<T: Bounded> LowerBounded for T {
+    fn min_value() -> T {
+        Bounded::min_value()
+    }
+}
+
+/// Numbers which have upper bounds
+pub trait UpperBounded {
+    /// Returns the largest finite number this type can represent
+    fn max_value() -> Self;
+}
+
+// FIXME: With a major version bump, this should be a supertrait instead
+impl<T: Bounded> UpperBounded for T {
+    fn max_value() -> T {
+        Bounded::max_value()
+    }
+}
+
 macro_rules! bounded_impl {
     ($t:ty, $min:expr, $max:expr) => {
         impl Bounded for $t {