feat: Add DiagonalOfMultiplication method (#40)

limakzi · Aug 26, 2024 · 13a1718 · 13a1718
1 parent 6fc4639
commit 13a1718
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Showing 2 changed files with 18 additions and 2 deletions.
diff --git a/lib/properties.gd b/lib/properties.gd
@@ -1,3 +1,15 @@
+#! @Arguments M
+#! @Description
+#! identifies associativity index of <A>M</A>.
+#!
+#! @BeginExampleSession
+#! gap> List(AllSmallAntimagmas(3), M -> DiagonalOfMultiplicationTable((M)));                
+#! [ [ 2, 1, 1 ], [ 2, 1, 1 ], [ 2, 3, 2 ], [ 2, 1, 1 ], [ 2, 1, 1 ], [ 2, 1, 2 ], [ 2, 3, 2 ], [ 2, 1, 2 ], 
+#! [ 2, 3, 1 ], [ 2, 3, 1 ] ]
+#! @EndExampleSession
+#!
+DeclareAttribute( "AssociativityIndex", IsMagma );
+
 #! @Arguments M
 #! @Description
 #! indentifies associativity index of <A>M</A>.
@@ -14,8 +26,7 @@
 #! gap> AssociativityIndex(OneSmallGroup(4)) = 4 ^ 3;
 #! true
 #! @EndExampleSession
-#!
-DeclareAttribute( "AssociativityIndex", IsMagma );
+DeclareAttribute( "DiagonalOfMultiplicationTable", IsMagma);
 
 #! @Arguments M
 #! @Description

diff --git a/lib/properties.gi b/lib/properties.gi
@@ -11,6 +11,11 @@ InstallGlobalFunction(AllSubmagmas,
         return result;
 end);
 
+InstallMethod(DiagonalOfMultiplicationTable, "for a magma", [IsMagma],
+    function(M)
+        return DiagonalOfMatrix(MultiplicationTable(M));
+end);
+
 InstallMethod(AssociativityIndex, "for a magma", [IsMagma],
     function(M)
         return Size(Filtered(Tuples(M, 3), t -> (t[1] * t[2]) * t[3] = t[1] * (t[2] * t[3])));