From 32a7a19cd84fe825652488a75c09e40915e85e19 Mon Sep 17 00:00:00 2001
From: Max Horn <max@quendi.de>
Date: Mon, 24 Mar 2025 01:10:05 +0100
Subject: [PATCH 1/2] WIP: Add AddMatrixRight/Left, MultMatrixRight/Left

---
 lib/matobj.gi  | 41 +++++++++++++++++++++++++++++++++++++++++
 lib/matobj2.gd | 21 +++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/lib/matobj.gi b/lib/matobj.gi
index d397728233..418196dd78 100644
--- a/lib/matobj.gi
+++ b/lib/matobj.gi
@@ -1878,6 +1878,47 @@ InstallMethod( SwapMatrixColumns, "for a mutable matrix object, and two column n
   end );
 
 
+############################################################################
+
+InstallMethod( AddMatrixRight, "for a mutable matrix object, a matrix object and a scalar",
+  [ IsMatrixOrMatrixObj and IsMutable, IsMatrixOrMatrixObj, IsObject ],
+  function( dstmat, srcmat, scalar )
+    local i, j;
+#     Assert(0, NrRows(dstmat) = NrRows(srcmat));
+#     Assert(0, NrCols(dstmat) = NrCols(srcmat));
+    for i in [1..NrRows(dstmat)] do
+      for j in [1..NrCols(dstmat)] do
+        dstmat[i,j] := dstmat[i,j] + srcmat[i,j] * scalar;
+      od;
+    od;
+  end );
+
+InstallEarlyMethod( AddMatrixRight,
+  function( dstmat, srcmat, scalar )
+    local i;
+    if IsPlistRep(dstmat) and IsPlistRep(srcmat) then
+  #     Assert(0, NrRows(dstmat) = NrRows(srcmat));
+#     Assert(0, NrCols(dstmat) = NrCols(srcmat));
+      for i in [1..NrRows(dstmat)] do
+        AddRowVector(dstmat[i], srcmat[i], scalar);
+      od;
+    else
+      TryNextMethod();
+    fi;
+  end );
+
+InstallMethod( AddMatrixRight, "for a mutable 8bit matrix, an 8bit matrix and a scalar",
+  [ Is8BitMatrixRep and IsMutable, Is8BitMatrixRep, IsFFE ],
+  function( dstmat, srcmat, scalar )
+    local i, j;
+#     Assert(0, NrRows(dstmat) = NrRows(srcmat));
+#     Assert(0, NrCols(dstmat) = NrCols(srcmat));
+    for i in [1..NrRows(dstmat)] do
+      ADD_COEFFS_VEC8BIT_3(dstmat[i], srcmat[i], scalar);
+    od;
+  end );
+
+
 ############################################################################
 ##  Fallback method for DeterminantMatrix
 InstallMethod(DeterminantMatrix, ["IsMatrixObj"],
diff --git a/lib/matobj2.gd b/lib/matobj2.gd
index fc73f88118..dafe15fbd3 100644
--- a/lib/matobj2.gd
+++ b/lib/matobj2.gd
@@ -2052,3 +2052,24 @@ DeclareOperationKernel( "SwapMatrixRows", [ IsMatrixOrMatrixObj and IsMutable, I
 ##  <#/GAPDoc>
 ##
 DeclareOperationKernel( "SwapMatrixColumns", [ IsMatrixOrMatrixObj and IsMutable, IsInt, IsInt ], SWAP_MAT_COLS );
+
+
+############################################################################
+##
+##
+##
+DeclareOperation( "AddMatrixRight", [ IsMatrixOrMatrixObj and IsMutable, IsMatrixOrMatrixObj, IsObject ] );
+#DeclareOperation( "AddMatrixLeft", [ IsMatrixOrMatrixObj and IsMutable, IsMatrixOrMatrixObj, IsObject ] );
+
+# TODO: which default, left or right?
+#DeclareSynonym( "AddMatrix", AddMatrixRowsLeft);
+
+############################################################################
+##
+##
+##
+#DeclareOperation( "MultMatrixRight", [ IsMatrixOrMatrixObj and IsMutable, IsMatrixOrMatrixObj, IsObject ] );
+#DeclareOperation( "MultMatrixLeft", [ IsMatrixOrMatrixObj and IsMutable, IsMatrixOrMatrixObj, IsObject ] );
+
+# TODO: which default, left or right?
+#DeclareSynonym( "MultMatrix", MultMatrixLeft);

From d1f06230794500221f93c4a799632231878a62c1 Mon Sep 17 00:00:00 2001
From: Max Horn <max@quendi.de>
Date: Wed, 9 Apr 2025 17:34:58 +0200
Subject: [PATCH 2/2] Update lib/matobj2.gd

---
 lib/matobj2.gd | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/matobj2.gd b/lib/matobj2.gd
index dafe15fbd3..5ac2e4d0fd 100644
--- a/lib/matobj2.gd
+++ b/lib/matobj2.gd
@@ -2068,8 +2068,8 @@ DeclareOperation( "AddMatrixRight", [ IsMatrixOrMatrixObj and IsMutable, IsMatri
 ##
 ##
 ##
-#DeclareOperation( "MultMatrixRight", [ IsMatrixOrMatrixObj and IsMutable, IsMatrixOrMatrixObj, IsObject ] );
-#DeclareOperation( "MultMatrixLeft", [ IsMatrixOrMatrixObj and IsMutable, IsMatrixOrMatrixObj, IsObject ] );
+#DeclareOperation( "MultMatrixRight", [ IsMatrixOrMatrixObj and IsMutable, IsObject ] );
+#DeclareOperation( "MultMatrixLeft", [ IsMatrixOrMatrixObj and IsMutable, IsObject ] );
 
 # TODO: which default, left or right?
 #DeclareSynonym( "MultMatrix", MultMatrixLeft);