(Isomorphism)SimplifiedFpGroup: use UseIsomorphismRelation

gap-system · Mar 2, 2022 · f2e6d42 · f2e6d42
1 parent 6982273
commit f2e6d42
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/lib/ghomfp.gi b/lib/ghomfp.gi
@@ -951,6 +951,7 @@ local H, pres,map,mapi,opt;
 
   # reconvert the Tietze presentation to a group presentation.
   H := FpGroupPresentation( pres );
+  UseIsomorphismRelation( G, H );
 
   if Length(GeneratorsOfGroup(H))>0 then
     map:=List(TzImagesOldGens(pres),

diff --git a/tst/testinstall/grpfp.tst b/tst/testinstall/grpfp.tst
@@ -1,4 +1,4 @@
-#@local a,b,c2,e,f,g,iter,l,s,F,rels,sub
+#@local a,b,c2,e,f,g,iter,l,s,F,rels,sub,iso,G
 gap> START_TEST("grpfp.tst");
 gap> f:= FreeGroup( "a", "b" );;  a := f.1;;  b := f.2;;
 gap> c2:= f / [ a*b*a^-2*b*a/b, (b^-1*a^3*b^-1*a^-3)^2*a ];;
@@ -105,8 +105,13 @@ gap> SimplifiedFpGroup(F/[GeneratorsOfGroup(F)[1]]);
 gap> F:=FreeGroup("a","b","c");;
 gap> rels:=ParseRelators(F,"a2,b3,c4,abC");
 [ a^2, b^3, c^4, a*b*c^-1 ]
-gap> IsomorphismSimplifiedFpGroup(F/rels);
+gap> g:=F/rels;;
+gap> Size(g);
+24
+gap> iso:=IsomorphismSimplifiedFpGroup(g);
 [ a, b, c ] -> [ c*b^-1, b, c ]
+gap> HasSize(Image(iso));
+true
 
 # ClosureSubgroupNC will not force a triviality or membership test
 # if we do not know anything.