kalmar/Groups.jl
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create FreeGroup(::Alphabet) on the correct number of gens

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Marek Kaluba 2021-06-21 17:52:51 +02:00
parent 25934e70f4
commit 8cb64d947d
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2 changed files with 14 additions and 1 deletions
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11
src/new_types.jl
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@ -131,7 +131,16 @@ end
function FreeGroup(A::Alphabet)
@boundscheck @assert all(KnuthBendix.hasinverse(l, A) for l in KnuthBendix.letters(A))
return FreeGroup(KnuthBendix.letters(A), A)
ltrs = KnuthBendix.letters(A)
gens = Vector{eltype(ltrs)}()
invs = Vector{eltype(ltrs)}()
for l in ltrs
l ∈ invs && continue
push!(gens, l)
push!(invs, inv(A, l))
end
return FreeGroup(gens, A)
end
function FreeGroup(n::Integer)

4
test/fp_groups.jl
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@ -1,7 +1,11 @@
@testset "FPGroups" begin
A = Alphabet([:a, :A, :b, :B, :c, :C], [2,1,4,3,6,5])
@test New.FreeGroup(A) isa New.FreeGroup
@test sprint(show, New.FreeGroup(A)) == "free group on 3 generators"
F = New.FreeGroup([:a, :b, :c], A)
@test sprint(show, F) == "free group on 3 generators"
a,b,c = gens(F)
@test c*b*a isa New.FPGroupElement