From 17a33f2c20a6b29fa8e2ca1188b5d7e4db1dfa13 Mon Sep 17 00:00:00 2001
From: Dan Kortschak <dan@kortschak.io>
Date: Wed, 21 Nov 2018 14:32:31 +1030
Subject: [PATCH] mat: add Banded methods to Diagonal

---
 mat/diagonal.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mat/diagonal.go b/mat/diagonal.go
index 199d0c8e..26f707aa 100644
--- a/mat/diagonal.go
+++ b/mat/diagonal.go
@@ -16,6 +16,7 @@ var (
 	_         MutableDiagonal = diagDense
 	_         Triangular      = diagDense
 	_         Symmetric       = diagDense
+	_         SymBanded       = diagDense
 	_         Banded          = diagDense
 	_         RawBander       = diagDense
 	_         RawSymBander    = diagDense
@@ -30,6 +31,12 @@ type Diagonal interface {
 	// matrices to be used in functions taking symmetric inputs.
 	Diag() int
 	Symmetric() int
+
+	// Bandwidth and TBand are included in the Diagonal interface
+	// to allow the use of Diagonal types in banded functions.
+	// Bandwidth will always return (0, 0).
+	Bandwidth() (kl, ku int)
+	TBand() Banded
 }
 
 // MutableDiagonal is a Diagonal matrix whose elements can be set.