From 43ad81d4ddfac61c9511de601964fa25053d29ab Mon Sep 17 00:00:00 2001
From: kalmarek <kalmar@amu.edu.pl>
Date: Wed, 25 Mar 2020 04:19:02 +0100
Subject: [PATCH] separate GWords

---
 src/Groups.jl | 50 +-------------------------------------------------
 src/types.jl  | 29 +++++++++++++++++++++++++++++
 src/words.jl  | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+), 49 deletions(-)
 create mode 100644 src/words.jl

diff --git a/src/Groups.jl b/src/Groups.jl
index 76d3752..45c7b54 100644
--- a/src/Groups.jl
+++ b/src/Groups.jl
@@ -17,53 +17,10 @@ using Markdown
 include("types.jl")
 include("gsymbols.jl")
 include("fallbacks.jl")
+include("words.jl")
 
 @doc doc"""
-
-
-abstract type GWord{T<:GSymbol} <: GroupElem end
-
-# fallback definitions
-Base.eltype(w::GW) where GW<:GWord = eltype(GW)
-@doc doc"""
-    W::GroupWord{T} <: GWord{T<:GSymbol} <:GroupElem
-> Basic representation of element of a finitely presented group. `W.symbols`
-> fieldname contains particular group symbols which multiplied constitute a
-> group element, i.e. a word in generators.
-> As reduction (inside group) of such word may be time consuming we provide
-> `savedhash` and `modified` fields as well:
-> hash (used e.g. in the `unique` function) is calculated by reducing the word,
-> setting `modified` flag to `false` and computing the hash which is stored in
-> `savedhash` field.
-> whenever word `W` is changed `W.modified` is set to `false`;
-> Future comparisons don't perform reduction (and use `savedhash`) as long as
-> `modified` flag remains `false`.
-
 """
-mutable struct GroupWord{T} <: GWord{T}
-    symbols::Vector{T}
-    modified::Bool
-    savedhash::UInt
-    parent::Group
-
-    function GroupWord{T}(symbols::Vector{T}) where {T}
-       return new{T}(symbols, true, zero(UInt))
-    end
-end
-
-syllablelength(w::GWord) = length(w.symbols)
-syllables(w::GWord) = w.symbols
-ismodified(w::GWord) = w.modified
-setmodified!(w::GWord) = (w.modified = true; w)
-unsetmodified!(w::GWord) = (w.modified = false; w)
-Base.one(w::GWord) = one(parent(w))
-
-
-###############################################################################
-#
-#   Includes
-#
-###############################################################################
 
 include("FreeGroup.jl")
 include("FPGroups.jl")
@@ -86,11 +43,6 @@ parent(w::GWord{T}) where {T<:GSymbol} = w.parent
 #
 ###############################################################################
 
-GroupWord(s::T) where {T<:GSymbol} = GroupWord{T}(T[s])
-GroupWord{T}(s::T) where {T<:GSymbol} = GroupWord{T}(T[s])
-GroupWord(w::GroupWord{T}) where {T<:GSymbol} = w
-convert(::Type{GroupWord{T}}, s::T) where {T<:GSymbol} = GroupWord{T}(T[s])
-
 ###############################################################################
 #
 #   Basic manipulation
diff --git a/src/types.jl b/src/types.jl
index 9d93fc8..320b04f 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -9,3 +9,32 @@ abstract type AbstractFPGroup <: Group end
 > * `pow` which is the (multiplicative) exponent of a symbol.
 """
 abstract type GSymbol end
+
+abstract type GWord{T<:GSymbol} <: GroupElem end
+
+@doc doc"""
+    W::GroupWord{T} <: GWord{T<:GSymbol} <:GroupElem
+> Basic representation of element of a finitely presented group. `W.symbols`
+> fieldname contains particular group symbols which multiplied constitute a
+> group element, i.e. a word in generators.
+> As reduction (inside group) of such word may be time consuming we provide
+> `savedhash` and `modified` fields as well:
+> hash (used e.g. in the `unique` function) is calculated by reducing the word,
+> setting `modified` flag to `false` and computing the hash which is stored in
+> `savedhash` field.
+> whenever word `W` is changed `W.modified` is set to `false`;
+> Future comparisons don't perform reduction (and use `savedhash`) as long as
+> `modified` flag remains `false`.
+
+"""
+
+mutable struct GroupWord{T} <: GWord{T}
+    symbols::Vector{T}
+    modified::Bool
+    savedhash::UInt
+    parent::Group
+
+    function GroupWord{T}(symbols::Vector{<:GSymbol}) where T
+       return new{T}(symbols, true, zero(UInt))
+    end
+end
diff --git a/src/words.jl b/src/words.jl
new file mode 100644
index 0000000..ab08337
--- /dev/null
+++ b/src/words.jl
@@ -0,0 +1,39 @@
+syllablelength(w::GWord) = length(w.symbols)
+syllables(w::GWord) = w.symbols
+ismodified(w::GWord) = w.modified
+setmodified!(w::GWord) = (w.modified = true; w)
+unsetmodified!(w::GWord) = (w.modified = false; w)
+savehash!(w::GWord, h::UInt) = (w.savedhash = h; w)
+savedhash(w::GWord) = w.savedhash
+parent(w::GWord) = w.parent
+hasparent(w::GWord) = isdefined(w, :parent)
+setparent!(w::GWord, G::AbstractFPGroup) = (w.parent = G; w)
+
+Base.isempty(w::GWord) = isempty(syllables(w))
+Base.isone(w::GWord) = (freereduce!(w); isempty(w))
+Base.one(w::GWord) = one(parent(w))
+
+function Base.iterate(w::GWord, state=(syllable=1, pow=1))
+    state.syllable > syllablelength(w) && return nothing
+    next = iterate(syllables(w)[state.syllable], state.pow)
+    next === nothing && return iterate(w, (syllable=state.syllable+1, pow=1))
+    return first(next), (syllable=state.syllable, pow=last(next))
+end
+
+Base.eltype(::Type{<:GWord{T}}) where T = T
+Base.length(w::GWord) = isempty(w) ? 0 : sum(length, syllables(w))
+Base.size(w::GWord) = (length(w),)
+Base.lastindex(w::GWord) = length(w)
+
+Base.@propagate_inbounds function Base.getindex(w::GWord, i::Integer)
+    csum = 0
+    idx = 0
+    @boundscheck 0 < i <= length(w) || throw(BoundsError(w, i))
+    while csum < i
+        idx += 1
+        csum += length(syllables(w)[idx])
+    end
+    return first(syllables(w)[idx])
+end
+
+# no setindex! for syllable based words