Fix FixedPointNumber: zero is not positive.

primitives/arithmetic/src/fixed_point.rs

@@ -214,12 +214,12 @@ pub trait FixedPointNumber:
 		self.into_inner() == Self::Inner::one()
 	}
 
-	/// Checks if the number is positive.
+	/// Returns `true` if `self` is positive and `false` if the number is zero or negative.
 	fn is_positive(self) -> bool {
-		self.into_inner() >= Self::Inner::zero()
+		self.into_inner() > Self::Inner::zero()
 	}
 
-	/// Checks if the number is negative.
+	/// Returns `true` if `self` is negative and `false` if the number is zero or positive.
 	fn is_negative(self) -> bool {
 		self.into_inner() < Self::Inner::zero()
 	}
@@ -1393,6 +1393,23 @@ macro_rules! implement_fixed {
 				assert_eq!(d.checked_div(&$name::zero()), None);
 			}
 
+			#[test]
+			fn is_positive_negative_works() {
+				let one = $name::one();
+				assert!(one.is_positive());
+				assert!(!one.is_negative());
+
+				let zero = $name::zero();
+				assert!(!zero.is_positive());
+				assert!(!zero.is_negative());
+
+				if $signed {
+					let minus_one = $name::saturating_from_integer(-1);
+					assert!(minus_one.is_negative());
+					assert!(!minus_one.is_positive());
+				}
+			}
+
 			#[test]
 			fn trunc_works() {
 				let n = $name::saturating_from_rational(5, 2).trunc();