44 lines
1.6 KiB
Julia
44 lines
1.6 KiB
Julia
abstract type AbstractFPGroup <: Group end
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@doc doc"""
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::GSymbol
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> Represents a syllable.
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> Abstract type which all group symbols of AbstractFPGroups should subtype. Each
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> concrete subtype should implement fields:
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> * `id` which is the `Symbol` representation/identification of a symbol
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> * `pow` which is the (multiplicative) exponent of a symbol.
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"""
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abstract type GSymbol end
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abstract type GWord{T<:GSymbol} <: GroupElem end
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@doc doc"""
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W::GroupWord{T} <: GWord{T<:GSymbol} <:GroupElem
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> Basic representation of element of a finitely presented group. `W.symbols`
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> fieldname contains particular group symbols which multiplied constitute a
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> group element, i.e. a word in generators.
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> As reduction (inside group) of such word may be time consuming we provide
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> `savedhash` and `modified` fields as well:
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> hash (used e.g. in the `unique` function) is calculated by reducing the word,
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> setting `modified` flag to `false` and computing the hash which is stored in
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> `savedhash` field.
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> whenever word `W` is changed `W.modified` is set to `false`;
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> Future comparisons don't perform reduction (and use `savedhash`) as long as
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> `modified` flag remains `false`.
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"""
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mutable struct GroupWord{T} <: GWord{T}
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symbols::Vector{T}
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modified::Bool
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savedhash::UInt
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parent::Group
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function GroupWord{T}(symbols::AbstractVector{<:GSymbol}) where T
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return new{T}(symbols, true, zero(UInt))
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end
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GroupWord(v::AbstractVector{T}) where T<:GSymbol = GroupWord{T}(v)
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GroupWord{T}(s::GSymbol) where T<:GSymbol = GroupWord{T}(T[s])
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GroupWord(s::T) where T<:GSymbol = GroupWord{T}(s)
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end
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