fix side-effects of rebasing and of changes in GAP

Author: ThomasBreuer

lib/classic.gi

@@ -784,17 +784,17 @@ InstallMethod( SpecialUnitaryGroupCons,
     g:= SpecialUnitaryGroupCons( filt, d, q );
     stored:= InvariantSesquilinearForm( g ).matrix;
 
-    # If the prescribed form fits then just return.
-    if stored = form!.matrix then
-      return g;
-    fi;
-
     # Check that 'form' lives over the intended field.
     F:= GF(q^2);
     if not IsSubset( F, form!.basefield ) then
       Error( "the defining field of <form> does not fit to <q>" );
     fi;
 
+    # If the prescribed form fits then just return.
+    if stored = form!.matrix then
+      return g;
+    fi;
+
     # Compute a base change matrix.
     # (Check that the canonical forms are equal.)
     wanted:= HermitianFormByMatrix( stored, F );
@@ -928,6 +928,11 @@ InstallMethod( SymplecticGroupCons,
     g:= SymplecticGroupCons( filt, d, F );
     stored:= InvariantBilinearForm( g ).matrix;
 
+    # Check that 'form' lives over the intended field.
+    if not IsSubset( F, form!.basefield ) then
+      Error( "the defining field of <form> does not fit to <q>" );
+    fi;
+
     # If the prescribed form fits then just return.
     form_matrix:= Matrix( form!.matrix, stored );
 #T This 'Matrix' call should become unnecessary.
@@ -936,12 +941,6 @@ InstallMethod( SymplecticGroupCons,
       return g;
     fi;
 
-    # Check that 'form' lives over the intended field.
-    F:= GF(q);
-    if not IsSubset( F, form!.basefield ) then
-      Error( "the defining field of <form> does not fit to <q>" );
-    fi;
-
     # Compute a base change matrix.
     # (Check that the canonical forms are equal.)
     wanted:= BilinearFormByMatrix( stored, F );
@@ -964,7 +963,7 @@ InstallMethod( SymplecticGroupCons,
       SetName( gg, Name( g ) );
     fi;
 
-    SetInvariantBilinearForm( gg, rec( matrix:= form!.matrix,
+    SetInvariantBilinearForm( gg, rec( matrix:= form_matrix,
                                        baseDomain:= F ) );
     if HasIsFullSubgroupGLorSLRespectingBilinearForm( g ) then
       SetIsFullSubgroupGLorSLRespectingBilinearForm( gg,

lib/conformal.gi

@@ -14,7 +14,7 @@ InstallMethod( ConformalSymplecticGroupCons,
   { filt, G } -> ConformalSymplecticGroupCons( filt,
                    BilinearFormByMatrix(
                      InvariantBilinearForm( G ).matrix,
-                     Forms_FieldOfDefinition( G, InvariantBilinearForm( G ) ) ) ) );
+                     Forms_FieldOfDefinition( InvariantBilinearForm( G ), G ) ) ) );
 
 InstallMethod( ConformalSymplecticGroupCons,
   "matrix group for group with form",
@@ -23,7 +23,7 @@ InstallMethod( ConformalSymplecticGroupCons,
   { filt, G } -> ConformalSymplecticGroupCons( filt,
                    BilinearFormByMatrix(
                      InvariantBilinearFormUpToScalars( G ).matrix,
-                     Forms_FieldOfDefinition( G, InvariantBilinearFormUpToScalars( G ) ) ) ) );
+                     Forms_FieldOfDefinition( InvariantBilinearFormUpToScalars( G ), G ) ) ) );
 
 InstallMethod( ConformalSymplecticGroupCons,
   "matrix group for form",

tst/adv/conformal.tst

@@ -46,7 +46,8 @@ gap> for q in [ 2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 23, 25 ] do
 >            Error( "problem with CSp(", d, ",", q, ")" );
 >          fi;
 > 
->          if Size( g ) < 10^7 then
+>          if Size( g ) < 10^7 and filt = IsPlistRep then
+> # Change this as soon as also `IsPlistMatrixRep` works!
 >            pg:= ConformalSymplecticGroup( IsPermGroup, d, q );
 >            if Size( g ) <> Size( pg ) then
 >              Error( "problem with CSp(IsPermGroup, ", d, ",", q, ")" );