subgroup and sub

[FriedrichRober]

It's a bit confusing that there are two commands sub and subgroup.

[fieker]

On Wed, Sep 08, 2021 at 01:18:05AM -0700, FriedrichRober wrote: It's a bit confusing that there are two commands `sub` and `subgroup`.

sub works for "all" structures, ie. modules, number fields, ... subgroup, by choice of name, only for groups.

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[thofma]

subgroup is only used in Hecke for one specific type of group. We should just rename it.

[FriedrichRober]

The problem I had was that subgroup does not work for all groups. For example:

julia> G = symmetric_group(5)
Sym( [ 1 .. 5 ] )

julia> x = perm(G, [2,3,1,5,4])
(1,2,3)(4,5)

julia> H, iota = subgroup(G, [x])
ERROR: MethodError: no method matching subgroup(::PermGroup, ::Vector{PermGroupElem})
Stacktrace:
 [1] top-level scope
   @ REPL[8]:1

julia> H, iota = sub(G, [x])
(Group([ (1,2,3)(4,5) ]), Group homomorphism from 
Group([ (1,2,3)(4,5) ])
to
Sym( [ 1 .. 5 ] ))

[thofma]

Will be fixed by thofma/Hecke.jl#396.

[thofma]

Let's keep it open until the changes made it to Oscar.

[fingolfin]

There was an Oscar release in the meantime and I think this is really resolved now