Prefer using BaseDomain over BaseField

However, leave the documentation untouched (at least for now), as
cvec users certainly are used to using BaseField

gap/cmat.gi

@@ -905,7 +905,7 @@ InstallMethod( ExtractSubMatrix, "for a compressed 8bit matrix",
   function(m, rows, cols)
     local mm,s;
     mm := m{rows}{cols};
-    s := Size(BaseField(m));
+    s := Size(BaseDomain(m));
     ConvertToMatrixRep(mm,s);
     return mm;
   end );
@@ -1219,13 +1219,16 @@ InstallMethod( BaseDomain, "for a cmat", [IsCMatRep],
     return c![CVEC_IDX_GF];
   end);
 
+# compatibility with GAP <= 4.11
+if IsBound(BaseField) and not IsIdenticalObj(BaseDomain, BaseField) then
 InstallMethod( BaseField, "for a cmat", [IsCMatRep],
   function(m)
     local c;
     c := m!.vecclass;
     return c![CVEC_IDX_GF];
   end);
-
+fi;
+
 InstallMethod(FieldOfMatrixList,
   [IsListOrCollection and IsFFECollCollColl],1,
   function(l)
@@ -2725,7 +2728,7 @@ InstallGlobalFunction( CVEC_ValueLaurentPoly,
     if not(IsOne(s)) then
         for j in [1..n] do MultVector(val[j],s); od;
     fi;
-    o := One(BaseField(x));
+    o := One(BaseDomain(x));
     while true do
         i := i - 1;
         # Add a multiple of the identity:

gap/cvec.gi

@@ -1073,14 +1073,17 @@ InstallMethod( BaseDomain, "for cvecs", [IsCVecRep],
     c := DataObj(v);
     return c![CVEC_IDX_GF];
   end);
-
+
+# compatibility with GAP <= 4.11
+if IsBound(BaseField) and not IsIdenticalObj(BaseDomain, BaseField) then
 InstallMethod( BaseField, "for cvecs", [IsCVecRep],
   function(v)
     local c;
     c := DataObj(v);
     return c![CVEC_IDX_GF];
   end);
-
+fi;
+
 #############################################################################
 # Slicing:
 #############################################################################

gap/linalg.gi

@@ -662,7 +662,7 @@ InstallGlobalFunction( CVEC_MinimalPolynomial, function(m)
   d := NumberRows(m);
   b := EmptySemiEchelonBasis(m);
   pivs := [1..d];
-  f := BaseField(m);
+  f := BaseDomain(m);
   poly := One(PolynomialRing(f,[1]));
   o := One(f);
   fam := FamilyObj(o);

gap/quarry.g

@@ -7,7 +7,7 @@ InstallMethod( LazyGreaser, "for a vector and a positive grease level",
   function( vecs, lev )
     local lg;
     lg := rec( vecs := vecs, tab := vecs{[]}, ind := [], lev := lev, 
-               fs := Size(BaseField(vecs)) );
+               fs := Size(BaseDomain(vecs)) );
     if lg.fs > 65536 then
         Error("Lazy grease only supported for fields with <= 65536 elements");
         return;
@@ -96,7 +96,7 @@ CVEC_TESTLAZY := function(m,lev)
   local erg,f,i,j,l,offset,newpos,poss,v,w;
   v := ShallowCopy(m[1]);
   l := LazyGreaser(m,lev);
-  f := BaseField(m);
+  f := BaseDomain(m);
   offset := Random(1,Length(m)-lev+1);
   offset := QuoInt(offset-1,lev)*lev + 1;  # make it congruent 1 mod lev
   for i in [1..10000] do
@@ -205,7 +205,7 @@ InstallGlobalFunction( CVEC_RelativeOrderPoly, function( m, v, subb, indetnr )
   # is bound.
   # The original v is untouched!
   local A,B,b,closed,d,dec,f,fam,i,l,lambda,o,ordpol,vcopy,vl,vv;
-  f := BaseField(m);
+  f := BaseDomain(m);
   o := One(f);
   fam := FamilyObj(o);
   b := EmptySemiEchelonBasis(v);
@@ -333,7 +333,7 @@ function( m, eps, verify, indetnr )
   A := [];   # base changes within each subquotient
   l := [];   # a list of semi echelon bases for the subquotients
   # order polynomial infrastructure (grows over time):
-  opi := rec( f := BaseField(m),
+  opi := rec( f := BaseDomain(m),
               d := [],
               ranges := [],
               rordpols := [],   # list of relative order polynomials
@@ -495,7 +495,7 @@ InstallGlobalFunction( CVEC_NewMinimalPolynomial, function( m, indetnr )
   A := [];   # base changes within each subquotient
   l := [];   # a list of semi echelon bases for the subquotients
   # order polynomial infrastructure (grows over time):
-  opi := rec( f := BaseField(m),
+  opi := rec( f := BaseDomain(m),
               d := [],
               ranges := [],
               rordpols := [],   # list of relative order polynomials