real: implement std::iter::Sum

crates/cross/src/real.rs

@@ -18,6 +18,12 @@ pub trait ToFloat {
     fn to_f64(&self) -> f64 {
         self.to_f32() as _
     }
+    fn to_r32(&self) -> R32 {
+        R32::new(self.to_f32())
+    }
+    fn to_r64(&self) -> R64 {
+        R64::new(self.to_f64())
+    }
 }
 
 
@@ -383,6 +389,16 @@ impl<T: Real> Div for Finite<T> {
     }
 }
 
+#[cfg(feature = "iter")]
+impl<T: Real> std::iter::Sum for Finite<T> {
+    fn sum<I>(iter: I) -> Self
+    where
+        I: Iterator<Item = Self>
+    {
+        iter.fold(Self::zero(), |a, b| a + b)
+    }
+}
+
 
 impl<T: ToFloat> ToFloat for Finite<T> {
     fn to_f32(&self) -> f32 {