Update ViewString for rank-zero free groups/monoids

gap-system · Jun 11, 2021 · e9cf171 · e9cf171
1 parent 6062d54
commit e9cf171
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Showing 3 changed files with 7 additions and 3 deletions.
diff --git a/lib/grpfp.gi b/lib/grpfp.gi
@@ -5729,4 +5729,4 @@ InstallMethod( IndependentGeneratorsOfAbelianGroup,
   [ IsFpGroup and IsAbelian ],
   IndependentGeneratorsOfMaximalAbelianQuotientOfFpGroup );
 
-BindGlobal("TRIVIAL_FP_GROUP",FreeGroup(0,"TrivGp")/[]);
+BindGlobal( "TRIVIAL_FP_GROUP", FreeGroup(0) / [] );
diff --git a/lib/grpfree.gi b/lib/grpfree.gi
@@ -591,7 +591,9 @@ InstallMethod( ViewObj,
     [ IsFreeGroup ],
 function(G)
   if IsGroupOfFamily(G) then
-    if Length(GeneratorsOfGroup(G)) > GAPInfo.ViewLength * 10 then
+    if IsEmpty(GeneratorsOfGroup(G)) then
+      Print("<free group of rank zero>");
+    elif Length(GeneratorsOfGroup(G)) > GAPInfo.ViewLength * 10 then
       Print("<free group with ",Length(GeneratorsOfGroup(G))," generators>");
     else
       Print("<free group on the generators ",GeneratorsOfGroup(G),">");

diff --git a/lib/monofree.gi b/lib/monofree.gi
@@ -284,7 +284,9 @@ InstallMethod( ViewObj,
     "for a free monoid containing the whole family",
     [ IsMonoid and IsAssocWordCollection and IsWholeFamily ],
     function( M )
-    if GAPInfo.ViewLength * 10 < Length( GeneratorsOfMagmaWithOne( M ) ) then
+    if IsEmpty( GeneratorsOfMagmaWithOne( M ) ) then
+      Print( "<free monoid of rank zero>" );
+    elif GAPInfo.ViewLength * 10 < Length( GeneratorsOfMagmaWithOne( M ) ) then
       Print( "<free monoid with ", Length( GeneratorsOfMagmaWithOne( M ) ),
              " generators>" );
     else