Implement FeeRate SubAssign

units/src/fee_rate.rs

@@ -3,7 +3,7 @@
 //! Implements `FeeRate` and assoctiated features.
 
 use core::fmt;
-use core::ops::{Add, Sub, Div, Mul, AddAssign};
+use core::ops::{Add, Sub, Div, Mul, AddAssign, SubAssign};
 
 #[cfg(feature = "arbitrary")]
 use arbitrary::{Arbitrary, Unstructured};
@@ -224,6 +224,14 @@ impl AddAssign<&FeeRate> for FeeRate {
     fn add_assign(&mut self, rhs: &FeeRate) { self.0 += rhs.0 }
 }
 
+impl SubAssign for FeeRate {
+    fn sub_assign(&mut self, rhs: Self) { self.0 -= rhs.0 }
+}
+
+impl SubAssign<&FeeRate> for FeeRate {
+    fn sub_assign(&mut self, rhs: &FeeRate) { self.0 -= rhs.0 }
+}
+
 crate::impl_parse_str_from_int_infallible!(FeeRate, u64, from_sat_per_kwu);
 
 #[cfg(test)]
@@ -267,6 +275,17 @@ mod tests {
         assert_eq!(f, FeeRate(3));
     }
 
+    #[test]
+    fn sub_assign() {
+        let mut f = FeeRate(3);
+        f -= FeeRate(2);
+        assert_eq!(f, FeeRate(1));
+
+        let mut f = FeeRate(3);
+        f -= &FeeRate(2);
+        assert_eq!(f, FeeRate(1));
+    }
+
     #[test]
     fn fee_rate_const_test() {
         assert_eq!(0, FeeRate::ZERO.to_sat_per_kwu());