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#############################################################################
##
#W tree.gi automgrp package Yevgen Muntyan
#W Dmytro Savchuk
##
#Y Copyright (C) 2003 - 2018 Yevgen Muntyan, Dmytro Savchuk
##
#############################################################################
##
#M TopDegreeOfTree (<obj>)
##
InstallMethod(TopDegreeOfTree, "for [IsActingOnTree]", [IsActingOnTree],
function(obj)
local si;
si := SphericalIndex(obj);
if not IsEmpty(si.start) then
return si.start[1];
else
return si.period[1];
fi;
end);
#############################################################################
##
#M DegreeOfLevel (<obj>)
##
InstallMethod(DegreeOfLevel, "for [IsActingOnTree, IsPosInt]",
[IsActingOnTree, IsPosInt],
function(obj, k)
return AG_DegreeOfLevelInSphericalIndex(SphericalIndex(obj), k);
end);
#############################################################################
##
#M IsActingOnRegularTree(<obj>)
##
InstallMethod(IsActingOnRegularTree, "for [IsActingOnTree]",
[IsActingOnTree],
function(obj)
local si;
si := SphericalIndex(obj);
return IsEmpty(si.start) and Length(si.period) = 1;
end);
#############################################################################
##
#M DegreeOfTree(<obj>)
##
InstallMethod(DegreeOfTree, "for [IsActingOnTree]",
[IsActingOnTree],
function(obj)
if not IsActingOnRegularTree(obj) then Error("The object ",obj," is not acting on a regular tree"); fi;
return SphericalIndex(obj).period[1];
end);
#############################################################################
##
#M IsActingOnBinaryTree(<obj>)
##
InstallMethod(IsActingOnBinaryTree, "for [IsActingOnTree]",
[IsActingOnTree],
function(obj)
return IsActingOnRegularTree(obj) and DegreeOfTree(obj) = 2;
end);
#############################################################################
##
#M FixesLevel (<obj>, <k>)
##
## The most stupid method - just for case.
##
InstallMethod(FixesLevel, "for [IsActingOnTree, IsPosInt]",
[IsActingOnTree, IsPosInt],
function(obj, k)
local lev, v;
if HasIsSphericallyTransitive(obj) then
if IsSphericallyTransitive(obj) then
return false;
fi;
fi;
lev := Tuples([1..DegreeOfTree(obj)], k);
for v in lev do
if not FixesVertex(obj, v) then
return false;
else
Info(InfoAutomGrp, 3, "IsSphericallyTransitive(obj): false");
Info(InfoAutomGrp, 3, " obj fixes vertex", v);
Info(InfoAutomGrp, 3, " obj = ", obj);
SetIsSphericallyTransitive(obj, false);
fi;
od;
return true;
end);
#E
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