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#
# walrus: Computational Methods for Finitely Generated Monoids and Groups
#
#### Utility functions
# Pregroup presentation for triangle group
InstallGlobalFunction(pg_word,
{pg, l} -> List(l, x->pg[x]) );
InstallGlobalFunction(Repeat,
{n, l} -> ShallowCopy(Flat(ListWithIdenticalEntries(n,l))));
# MaxPowerK: Input a word (relator) v over X, output w such that w^k = v, k
# maximal with this property InstallGlobalFunction(MaxPowerK,
InstallGlobalFunction(MaxPowerK,
function(rel)
local len, d, divs, isrep,
checkrep;
len := Length(rel);
divs := ShallowCopy(DivisorsInt(len));
Remove(divs, 1);
checkrep := function(d)
local j,k;
for j in [1..d] do
for k in [1..(len / d) - 1] do
if rel[j] <> rel[j + k*d] then
return false;
fi;
od;
od;
return true;
end;
for d in divs do
if checkrep(d) then
return [ rel{[1..d]}, len / d ];
fi;
od;
return [ rel, 1 ];
end);
InstallGlobalFunction(WalrusTestStandard,
function()
List(DirectoriesPackageLibrary("walrus", "tst/standard"), TestDirectory);
end);
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