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Optimal Cloud Coloring & famous 4 color map

Four colors will print a map so adjacent states have different color. F# has clear concise code. Map has a list of pairs sharing a border. Incremental improvements in the code can be less use of key word 'function'. Since syntax is not ambiguous can it be fixed in the compiler? so '=function |' changes to '=|' ? Welcome to improve. Harrop,Mathias,Jack,Art,HR,fwaris,Don Syme, sffs... Thanks! Musa.Jahanghir@Live.com AVCLive1.com

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let p = ["a","b"; "a","c"; "b","d"]
let rec p2e    =function []->[]    |(a,b)::ps ->a::b:: p2e ps

let rec rNb i l=function []->false |p::ps -> (l,i)=p ||(i,l)=p || rNb l i ps
let rec cXl i  =function []->true  |l::ls -> not( rNb i l p)   && cXl   i ls

let rec xCg i  =function []->[[i]] |cl::cls -> if (cXl i cl) then (i::cl)::cls else cl:: xCg i cls
List.fold(fun a i->xCg i a) [] (p2e p |> List.distinct)//[["d";"a"];["c";"b"]]Musa.Jahanghir@Live.com

val p : (string * string) list

Full name: Script.p

val p2e : _arg1:('a * 'a) list -> 'a list

Full name: Script.p2e

val a : 'a

val b : 'a

val ps : ('a * 'a) list

val rNb : i:'a -> l:'a -> _arg1:('a * 'a) list -> bool (requires equality)

Full name: Script.rNb

val i : 'a (requires equality)

val l : 'a (requires equality)

val p : 'a * 'a (requires equality)

val ps : ('a * 'a) list (requires equality)

val cXl : i:string -> _arg1:string list -> bool

Full name: Script.cXl

val i : string

val l : string

val ls : string list

val not : value:bool -> bool

Full name: Microsoft.FSharp.Core.Operators.not

val xCg : i:string -> _arg1:string list list -> string list list

Full name: Script.xCg

val cl : string list

val cls : string list list

Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
  | ( [] )
  | ( :: ) of Head: 'T * Tail: 'T list
  interface IEnumerable
  interface IEnumerable<'T>
  member GetSlice : startIndex:int option * endIndex:int option -> 'T list
  member Head : 'T
  member IsEmpty : bool
  member Item : index:int -> 'T with get
  member Length : int
  member Tail : 'T list
  static member Cons : head:'T * tail:'T list -> 'T list
  static member Empty : 'T list

Full name: Microsoft.FSharp.Collections.List<_>

val fold : folder:('State -> 'T -> 'State) -> state:'State -> list:'T list -> 'State

Full name: Microsoft.FSharp.Collections.List.fold

val a : string list list

val distinct : list:'T list -> 'T list (requires equality)

Full name: Microsoft.FSharp.Collections.List.distinct

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More information

Link:	http://fssnip.net/7TW
Posted:	6 years ago
Author:	Musa Jahanghir
Tags:	#computationalgeometry