add isomorphism
#1243
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add isomorphism
#1243
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This is a follow-up to #1182. - deprecate `isomorphic_fp_group(G::GAPGroup)`, `isomorphic_pc_group(G::GAPGroup)`, `isomorphic_perm_group(G::GAPGroup)` in favour of `isomorphism(::Type{FPGroup}, G::GAPGroup)` `isomorphism(::Type{PcGroup}, G::GAPGroup)` `isomorphism(::Type{PermGroup}, G::GAPGroup)` - deprecate also (the undocumented) `isomorphic_group(::Type{T}, G::GAPGroup)` (does not occur in tests) in favour of `isomorphism` - added `isomorphism(::Type{FPGroup}, A::GrpAbFinGen)` `isomorphism(::Type{PcGroup}, A::GrpAbFinGen)` `isomorphism(::Type{PermGroup}, A::GrpAbFinGen)` - moved `_get_iso_function` and `isomorphic_group` from `sub.jl` to `homomorphisms.jl` - added tests for new conversions - adjusted tests to use `isomorphism` instead of the deprecated versions - added (::Type{T})(G::GAPGroup)
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the old versin is used - at least the Galois stuff has to be adjusted as well |
fingolfin
reviewed
Apr 6, 2022
| Return an isomorphism from `G` to a group of type `T`. | ||
| An exception is thrown if no such isomorphism exists. | ||
| """ | ||
| function isomorphism(::Type{T}, G::GAPGroup) where T <: Union{FPGroup, PcGroup, PermGroup} |
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Should we perhaps cache these isomorphisms, i.e.
Suggested change
| function isomorphism(::Type{T}, G::GAPGroup) where T <: Union{FPGroup, PcGroup, PermGroup} | |
| @attr function isomorphism(::Type{T}, G::GAPGroup) where T <: Union{FPGroup, PcGroup, PermGroup} |
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Caching is a good idea, but isomorphism takes two arguments, and @attr can deal only with unary functions.
(From this point of view, the old isomorphic_fp_group etc. were more suitable.)
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Yeah, we can't just use @attr, but we can still "manually" implement that caching. Anyway, not in this PR.
fingolfin
reviewed
Apr 6, 2022
| @@ -167,8 +167,7 @@ preimage(f::GAPGroupHomomorphism{S, T}, H::T) where S <: GAPGroup where T <: GAP | |||
| ## Groups created by isomorphisms | |||
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I really don't like this section title. Though I also don't have a great alternative suggestion... perhaps just
Suggested change
| ## Groups created by isomorphisms | |
| ## Group isomorphisms |
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This is a follow-up to #1182.
deprecate
isomorphic_fp_group(G::GAPGroup),isomorphic_pc_group(G::GAPGroup),isomorphic_perm_group(G::GAPGroup)in favour of
isomorphism(::Type{FPGroup}, G::GAPGroup)isomorphism(::Type{PcGroup}, G::GAPGroup)isomorphism(::Type{PermGroup}, G::GAPGroup)deprecate also (the undocumented)
isomorphic_group(::Type{T}, G::GAPGroup)(does not occur in tests) in favour of
isomorphismadded
isomorphism(::Type{FPGroup}, A::GrpAbFinGen)isomorphism(::Type{PcGroup}, A::GrpAbFinGen)isomorphism(::Type{PermGroup}, A::GrpAbFinGen)moved
_get_iso_functionandisomorphic_groupfrom
sub.jltohomomorphisms.jladded tests for new conversions
adjusted tests to use
isomorphisminstead of the deprecated versionsadded (::Type{T})(G::GAPGroup)