Restore trace

Author: termoshtt

src/lib.rs

@@ -60,5 +60,6 @@ pub mod triangular;
 pub mod generate;
 pub mod assert;
 pub mod norm;
+pub mod trace;
 
 pub mod prelude;

src/prelude.rs

@@ -1,13 +1,14 @@
 
-pub use types::*;
-pub use generate::*;
 pub use assert::*;
+pub use generate::*;
+pub use types::*;
 
-pub use qr::*;
-pub use svd::*;
+pub use cholesky::*;
+pub use eigh::*;
+pub use norm::*;
 pub use opnorm::*;
+pub use qr::*;
 pub use solve::*;
-pub use eigh::*;
-pub use cholesky::*;
+pub use svd::*;
+pub use trace::*;
 pub use triangular::*;
-pub use norm::*;

src/trace.rs

@@ -0,0 +1,23 @@
+
+use ndarray::*;
+
+use super::types::*;
+use super::error::*;
+use super::layout::*;
+
+pub trait Trace {
+    type Output;
+    fn trace(&self) -> Result<Self::Output>;
+}
+
+impl<A, S> Trace for ArrayBase<S, Ix2>
+    where A: Field,
+          S: Data<Elem = A>
+{
+    type Output = A;
+
+    fn trace(&self) -> Result<Self::Output> {
+        let (n, _) = self.square_layout()?.size();
+        Ok((0..n as usize).map(|i| self[(i, i)]).sum())
+    }
+}