Added documentation for NormalizerViaRadical.

doc/ref/groups.xml

@@ -587,7 +587,6 @@ see <Cite Key="BJR87"/>.
 
 </Section>
 
-
 <!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
 <Section Label="Tests for the Availability of Methods">
 <Heading>Tests for the Availability of Methods</Heading>
@@ -601,6 +600,14 @@ see <Cite Key="BJR87"/>.
 <#Include Label="CanComputeIsSubset">
 <#Include Label="KnowsHowToDecompose">
 
+</Section>
+
+<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
+<Section Label="Specific functions for Normalizer calculation">
+<Heading>Specific functions for Normalizer calculation</Heading>
+
+<#Include Label="NormalizerViaRadical">
+
 </Section>
 </Chapter>
 

lib/grp.gd

@@ -4528,6 +4528,35 @@ DeclareGlobalFunction("GroupEnumeratorByClosure");
 DeclareOperation( "LowIndexSubgroups",
     [ IsGroup, IsPosInt ] );
 
+#############################################################################
+##
+#F  NormalizerViaRadical(<G>,<S>)
+##
+##  <#GAPDoc Label="NormalizerViaRadical">
+##  <ManSection>
+##  <Func Name="NormalizerViaRadical" Arg='G,S'/>
+##
+##  <Description>
+##  This function implements a particular approach, following the
+##  SolvableRadical paradigm, for calculating the
+##  normalizer of a subgroup <A>S</A> in <A>G</A>. It is at the moment
+##  provided only as a separate function, and not as method for the operation
+##  <C>Normalizer</C>, as it can often be slower than other built-in routines.
+##  In certain hard cases (non-solvable groups with nontrivial radical), however
+##  its performance is substantially superior.  The function thus provided as a
+##  non-automated tool for advanced users.
+##  <Example><![CDATA[
+##  gap> g:=TransitiveGroup(30,2030);;
+##  gap> s:=SylowSubgroup(g,5);;
+##  gap> Size(NormalizerViaRadical(g,s));
+##  28800
+##  ]]></Example>
+##  </Description>
+##  </ManSection>
+##  <#/GAPDoc>
+##
+DeclareGlobalFunction("NormalizerViaRadical");
+
 #############################################################################
 ##
 #E

lib/norad.gi

@@ -378,7 +378,7 @@ local expandvec,bassrc,basimg,transl,getbasimg,gettransl,myact2;
 end);
 
 # main normalizer routine
-BindGlobal("NormalizerViaRadical",function(G,U)
+InstallGlobalFunction(NormalizerViaRadical,function(G,U)
 local sus,ser,len,factorhom,uf,n,d,up,mran,nran,mpcgs,pcgs,pcisom,nf,ng,np,sub,
   central,f,ngm,npm,no2pcgs,part,stb,mods,famo,part0,nopcgs,uff,ufg,prev,
   famo2,ufr,dims,vecs,ovecs,vecsz,l,prop,properties,clusters,clusterspaces,