Colouring problem :
Hello, I'm trying to implement a bool function that returns true when a color can be extended to a country and false otherwise but I'm having trouble working with sets as we cannot pattern match them...
My code :
type Country = string;;
type Chart = Set<Country*Country>;;
type Colour = Set<Country>;;
type Colouring = Set<Colour>;;
(* This is how you tell that two countries are neghbours. It requires a chart.*)
let areNeighbours ct1 ct2 chart =
Set.contains (ct1,ct2) chart || Set.contains (ct2,ct1) chart;;
(* val areNeighbours :
ct1:'a -> ct2:'a -> chart:Set<'a * 'a> -> bool when 'a : comparison
(* The colour col can be extended by the country ct when they are no neighbours
according to chart.*)
let canBeExtBy (col:Colouring) (ct:Country) (chart:Chart) = col |> Set.fold (fun x -> (if (areNeighbours x ct chart) then true else false))
What is expected : we need to check if ct is a neighbour of any country in the col (assuming there are countries in the col), according to the neighbourhood defined in the chart.
chart = set
[("Andorra", "Benin"); ("Andorra", "Canada"); ("Andorra", "Denmark");
("Benin", "Canada"); ("Benin", "Denmark"); ("Canada", "Denmark");
("Estonia", "Canada"); ("Estonia", "Denmark"); ("Estonia", "Finland");
col = set
canBeExt should return false when when
ct = "Benin" or "Canada" or "Denmark" etc... As Andorra share a border with those countries and thus they cannot be coloured in the same colour as Andora.
Obviously I have a type error in canBeExtBy as I'm trying to return a bool and it's expecting 'a:Colouring.
I don't know how to implement it..
Thanks for your help !