The priority queue in Base is different from priority queues in other
languages.
I think you can use a plain priority queue (or heap) defined the
DataStructures.jl package.
To pair priority and state, `priority => state` would be helpful. This
paired values are ordered by the first element (priority) and then the
second element (state). So you can push and pop according to the priority.
Here is an example:
julia> Base.isless(s1::State, s2::State) = isless(s1.a, s1.a) || (s1.a == s2
.b && isless(s
1.a, s2.b))
isless (generic function with 32 methods)
julia> h = binary_minheap(Pair{Int,State})
DataStructures.BinaryHeap{Pair{Int64,State},DataStructures.LessThan}(
DataStructures.LessTh
an(),Pair{Int64,State}[])
julia> push!(h, 4 => State(5, 3))
julia> push!(h, 2 => State(5, 3))
julia> top(h)
2=>State(5,3)
julia> pop!(h)
2=>State(5,3)
julia> top(h)
4=>State(5,3)
On Friday, January 8, 2016 at 6:32:11 PM UTC+9, Tomas Lycken wrote:
>
> I tried this today:
>
> immutable State
> a::Int
> b::Int
> end
>
> import Base.Collections: PriorityQueue, enqueue!, dequeue!, peek
>
> pq = PriorityQueue(Int,Int)
>
> enqueue!(pq, State(5,3), 4)
> enqueue!(pq, State(5,3), 2)
>
> but it fails with the error
>
> LoadError: ArgumentError: PriorityQueue keys must be unique
>
> I assume this is because the states are immutable, and thus compare equal
> if all their values compare equal. Is there a way to make a priority queue
> insert the same state on several priorities, i.e. to support my example
> above?
>
> // T
>
>
