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add rewriting function to AbstractFPGroups

This commit is contained in:
Marek Kaluba 2021-05-05 02:32:27 +02:00
parent 9d7596acf1
commit 288f06c070
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2 changed files with 9 additions and 4 deletions

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@ -13,11 +13,14 @@ using Random
An Abstract type representing finitely presented groups. Every instance `` must implement An Abstract type representing finitely presented groups. Every instance `` must implement
* `KnuthBendix.alphabet(G::MyFPGroup)` * `KnuthBendix.alphabet(G::MyFPGroup)`
* `rewriting(G::MyFPGroup)` : return the rewriting object which must implement
> `KnuthBendix.rewrite_from_left!(u, v, rewriting(G))`.
By default `alphabet(G)` is returned, which amounts to free rewriting in `G`.
By default `word_type(::Type{MyFPGroup}) = Word{UInt16}` returns the default AbstractFPGroup may also override `word_type(::Type{MyFPGroup}) = Word{UInt16}`,
word type used for group elements. You may wish to override this if e.g. to which controls the word type used for group elements. If if your group has less
than `255` generators you may define
> `word_type(::Type{MyFPGroup}) = Word{UInt8}` > `word_type(::Type{MyFPGroup}) = Word{UInt8}`
if your group has less than `255` generators.
""" """
abstract type AbstractFPGroup <: GroupsCore.Group end abstract type AbstractFPGroup <: GroupsCore.Group end
@ -25,6 +28,8 @@ word_type(G::AbstractFPGroup) = word_type(typeof(G))
# the default: # the default:
word_type(::Type{<:AbstractFPGroup}) = Word{UInt16} word_type(::Type{<:AbstractFPGroup}) = Word{UInt16}
rewriting(G::AbstractFPGroup) = alphabet(G)
function (G::AbstractFPGroup)(word::AbstractVector{<:Integer}) function (G::AbstractFPGroup)(word::AbstractVector{<:Integer})
@boundscheck @assert all(l -> 1<= l <=length(KnuthBendix.alphabet(G)), word) @boundscheck @assert all(l -> 1<= l <=length(KnuthBendix.alphabet(G)), word)
return FPGroupElement(word_type(G)(word), G) return FPGroupElement(word_type(G)(word), G)

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@ -44,7 +44,7 @@ Defaults to the rewriting in the free group.
if isnormalform(g) && inv(alphabet(g), last(out)) != first(word(g)) if isnormalform(g) && inv(alphabet(g), last(out)) != first(word(g))
return append!(res, word(g)) return append!(res, word(g))
end end
return free_rewrite!(res, word(g), alphabet(g)) return KnuthBendix.rewrite_from_left!(res, word(g), rewriting(parent(g)))
end end
""" """