RingLists

A RingList is a list of distinct values that is unchanged by rotation. These can be created by giving a list of values or a one-dimensional array of values:

julia> using RingLists

julia> a = RingList(1,2,3,4);

julia> b = RingList([2,3,4,1]);

julia> a==b
true

julia> println(a)
[ 1 → 2 → 3 → 4 → 1 ]

Note the repeat of element 1 in the output showing that the list wraps around.

In this list, a stands for a RingList.

• length(a) gives the number of elements held in the RingList.
• keys(a) returns an iterator of the elements in a.
• haskey(a,x) checks if x is an element of the RingList.
• Vector(a) returns a one-dimensional array of the elements in a.
• Set(a) returns the elements of a (as an unordered collection).
• collect(a) returns the elements of a in an ordered list.
• copy(a) makes an independent copy of a.
• shuffle(a) returns a new RingList with the same elements as a but in randomized order.
• next(a,x) returns the next element after x in a; also a[x].
• previous(a,x) returns the element y with a[y]==x; also a(y).
• first(a) returns an element of a that is, if possible, the smallest element of a. Call first(a,false) to ignore trying to start at the smallest element. Fails if a is empty.
• delete!(a,x) removes x from the collection linking together its predecessor and successor.
• insert!(a,x) inserts the element a into the RingList. No guarantee where it will end up.
• insertbefore!(a,x,y) inserts x into a before y.
• insertafter!(a,x,y) inserts x into a after y. For example:

> a = RingList(1,2,3)
[ 1 → 2 → 3 → 1 ]

julia> insertafter!(a,99,2)

julia> a
[ 1 → 2 → 99 → 3 → 1 ]

• reverse(a) returns a new RingList with the elements reversed.

julia> a = RingList(1,2,3,4,5)
[ 1 → 2 → 3 → 4 → 5 → 1 ]

julia> b = reverse(a)
[ 1 → 5 → 4 → 3 → 2 → 1 ]

• firsts(a) returns a new RingList built by taking the first member of each element of a.

julia> a
[ (19, 20) → (20, 25) → (25, 31) → (31, 27) → (27, 19) → (19, 20) ]

julia> firsts(a)
[ 19 → 20 → 25 → 31 → 27 → 19 ]

RingList elements can be iterated:

julia> a = RingList(1,2,3,4,5)
[ 1 → 2 → 3 → 4 → 5 → 1 ]

julia> for x in a
       println(x)
       end
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