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fix the fix from #2656 #2684

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Aug 15, 2023
Merged

fix the fix from #2656 #2684

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23 changes: 15 additions & 8 deletions experimental/GModule/Cohomology.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -429,21 +429,28 @@ end
"""
The relations defining 'F' as an array of pairs.
"""
function _relations_by_generators(G::Oscar.GAPGroup)
f = GAPWrap.IsomorphismFpGroupByGenerators(G.X, GAPWrap.GeneratorsOfGroup(G.X))
@req f != GAP.Globals.fail "Could not convert group into a group of type FPGroup"
H = FPGroup(GAPWrap.Image(f))
return relations(H)
end

Oscar.relations(G::Oscar.GAPGroup) = _relations_by_generators(G)

function Oscar.relations(F::FPGroup)
is_full_fp_group(F) || return _relations_by_generators(F)
R = relators(F)
z = one(free_group(F))
return [(x, z) for x = R]
end

function Oscar.relations(G::Oscar.GAPGroup)
f = GAP.Globals.IsomorphismFpGroupByGenerators(G.X, GAPWrap.GeneratorsOfGroup(G.X))
@req f != GAP.Globals.fail "Could not convert group into a group of type FPGroup"
H = FPGroup(GAPWrap.Image(f))
return relations(H)
end

function Oscar.relations(G::PcGroup)
f = GAP.Globals.IsomorphismFpGroupByPcgs(GAP.Globals.Pcgs(G.X), GAP.Obj("g"))
# Call `GAPWrap.IsomorphismFpGroupByPcgs` only if `gens(G)` is a pcgs.
Ggens = GAPWrap.GeneratorsOfGroup(G.X)
Gpcgs = GAPWrap.Pcgs(G.X)
Ggens == Gpcgs || return _relations_by_generators(G)
f = GAPWrap.IsomorphismFpGroupByPcgs(Gpcgs, GAP.Obj("g"))
@req f != GAP.Globals.fail "Could not convert group into a group of type FPGroup"
H = FPGroup(GAPWrap.Image(f))
return relations(H)
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3 changes: 3 additions & 0 deletions src/GAP/wrappers.jl
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Expand Up @@ -202,6 +202,8 @@ GAP.@wrap IsWholeFamily(x::Any)::Bool
GAP.@wrap IsZero(x::Any)::Bool
GAP.@wrap IsZmodnZObj(x::Any)::Bool
GAP.@wrap IsZmodnZObjNonprimeCollection(x::Any)::Bool
GAP.@wrap IsomorphismFpGroupByGenerators(x::GapObj, y::GapObj)::GapObj
GAP.@wrap IsomorphismFpGroupByPcgs(x::GapObj, y::GapObj)::GapObj
GAP.@wrap Iterator(x::Any)::GapObj
GAP.@wrap KernelOfCharacter(x::GapObj, y::GapObj)::GapObj
GAP.@wrap LargestMovedPoint(x::Any)::Int
Expand Down Expand Up @@ -231,6 +233,7 @@ GAP.@wrap OnTuples(x::GapObj, y::GapObj)::GapObj
GAP.@wrap Order(x::Any)::GapInt
GAP.@wrap OrthogonalComponents(x::GapObj, y::GapObj, z::GapInt)::GapObj
GAP.@wrap OrthogonalDiscriminants(x::GapObj)::GapObj
GAP.@wrap Pcgs(x::GapObj)::GapObj
GAP.@wrap PermList(x::GapObj)::GapObj
GAP.@wrap Permuted(x::GapObj, y::GapObj)::GapObj
GAP.@wrap PolynomialByExtRep(x::GapObj, y::GapObj)::GapObj
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17 changes: 17 additions & 0 deletions test/Experimental/gmodule.jl
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Original file line number Diff line number Diff line change
@@ -1,3 +1,20 @@
@testset "Experimental.gmodule" begin
function testrels(G::Oscar.GAPGroup)
ggens = gens(G)
rels = relations(G)
return all(p -> map_word(p[1], ggens) == map_word(p[2], ggens), rels)
end

G = dihedral_group(8)
@test testrels(G) # full pc group
@test testrels(center(G)[1]) # subgroup of full pc group
F = FPGroup(G)
@test testrels(F) # full f.p. group
@test testrels(center(F)[1]) # subgroup of full f.p. group
@test testrels(PermGroup(G)) # nothing of the above
end


@testset "Experimental.gmodule" begin

G = small_group(7*3, 1)
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