Idea: Named variable declaration

[zsunberg]

This is an idea transferred from the previous IDEAS.md (#39 ):

Named Variables

It might also be more clear what is going on if we declared variables with names as shown in the example below.

This would be tougher to compile though, and it's not clear what the easiest way to express distributions or reward would be.

Ideas welcome!

mdp = @MDP begin
    xmax = 10
    ymax = 10

    @states begin
        x in 1:10
        y in 1:10
    end

    @actions begin
        dir in [:up, :down, :left, :right]
    end

    @reward rdict = Dict(
                    #XXX no idea how to define this in terms of x and y
                 )
    default_reward = 0.0

    @transition #XXX what is the most concise way to define the transition distribution??

    terminal = vals(reward)
    discount = 0.95

    initial
end