From b5faae0637da8cffb9b0835e8daab0747ee789b6 Mon Sep 17 00:00:00 2001
From: Max Horn <max@quendi.de>
Date: Thu, 11 Jul 2019 21:04:06 +0200
Subject: [PATCH] Fix IsUpperTriangularMat for non-square matrices; add tests

---
 lib/matrix.gi              |  4 ++--
 tst/testinstall/matrix.tst | 47 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 tst/testinstall/matrix.tst

diff --git a/lib/matrix.gi b/lib/matrix.gi
index 5223cc1889..00534f0a42 100644
--- a/lib/matrix.gi
+++ b/lib/matrix.gi
@@ -189,8 +189,8 @@ InstallMethod( IsUpperTriangularMat,
     function( mat )
     local  i, j, z;
     z:=ZeroOfBaseDomain(mat);
-    for i  in [ 1 .. NrRows( mat ) ]  do
-        for j  in [ 1 .. i-1]  do
+    for j  in [ 1 .. NrCols( mat ) ]  do
+        for i  in [ j+1 .. NrRows( mat ) ]  do
             if mat[i,j] <> z  then
                 return false;
             fi;
diff --git a/tst/testinstall/matrix.tst b/tst/testinstall/matrix.tst
new file mode 100644
index 0000000000..195bcb49f8
--- /dev/null
+++ b/tst/testinstall/matrix.tst
@@ -0,0 +1,47 @@
+#
+gap> IsDiagonalMat(NullMat(3, 3));
+true
+gap> IsDiagonalMat(NullMat(1, 3));
+true
+gap> IsDiagonalMat(NullMat(3, 1));
+true
+gap> IsDiagonalMat(IdentityMat(3));
+true
+gap> IsDiagonalMat([[1,1],[1,1]]);
+false
+gap> IsDiagonalMat([[1,0],[1,1]]);
+false
+gap> IsDiagonalMat([[1,1],[0,1]]);
+false
+
+#
+gap> IsUpperTriangularMat(NullMat(3, 3));
+true
+gap> IsUpperTriangularMat(NullMat(1, 3));
+true
+gap> IsUpperTriangularMat(NullMat(3, 1));
+true
+gap> IsUpperTriangularMat(IdentityMat(3));
+true
+gap> IsUpperTriangularMat([[1,1],[1,1]]);
+false
+gap> IsUpperTriangularMat([[1,0],[1,1]]);
+false
+gap> IsUpperTriangularMat([[1,1],[0,1]]);
+true
+
+#
+gap> IsLowerTriangularMat(NullMat(3, 3));
+true
+gap> IsLowerTriangularMat(NullMat(1, 3));
+true
+gap> IsLowerTriangularMat(NullMat(3, 1));
+true
+gap> IsLowerTriangularMat(IdentityMat(3));
+true
+gap> IsLowerTriangularMat([[1,1],[1,1]]);
+false
+gap> IsLowerTriangularMat([[1,0],[1,1]]);
+true
+gap> IsLowerTriangularMat([[1,1],[0,1]]);
+false