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# Frequency Sort

Sort a list by a frequency distribution. Frequency is calculated as per a a provided function. In the test case a list of lists is sorted by the frequency of the length of the lists.

 ``` 1: 2: 3: 4: 5: 6: 7: 8: 9: 10: 11: 12: 13: 14: ``` ``````let frequencySort l f = let fSort (d:System.Collections.Generic.Dictionary<_,_>) = let lens = l |> List.map List.length lens |> List.iter (fun i -> if d.ContainsKey(i) then d.[i] <- d.[i] + 1 else d.[i] <- 1) l |> List.sortBy (fun a -> d.[a.Length]) fSort (System.Collections.Generic.Dictionary()) let test = frequencySort [ ["a";"b";"c"]; ["d";"e"]; ["f";"g";"h"]; ["d";"e"]; ["i";"j";"k";"l"]; ["m";"n"]; ["o"] ] List.length // prints // [["i"; "j"; "k"; "l"]; ["o"]; ["a"; "b"; "c"]; ["f"; "g"; "h"]; ["d"; "e"]; // ["d"; "e"]; ["m"; "n"]] ``````
val frequencySort : l:'a list list -> f:'b -> 'a list list

Full name: Script.frequencySort
val l : 'a list list
val f : 'b
val fSort : (System.Collections.Generic.Dictionary<int,int> -> 'a list list)
val d : System.Collections.Generic.Dictionary<int,int>
namespace System
namespace System.Collections
namespace System.Collections.Generic
Multiple items
type Dictionary<'TKey,'TValue> =
new : unit -> Dictionary<'TKey, 'TValue> + 5 overloads
member Add : key:'TKey * value:'TValue -> unit
member Clear : unit -> unit
member Comparer : IEqualityComparer<'TKey>
member ContainsKey : key:'TKey -> bool
member ContainsValue : value:'TValue -> bool
member Count : int
member GetEnumerator : unit -> Enumerator<'TKey, 'TValue>
member GetObjectData : info:SerializationInfo * context:StreamingContext -> unit
member Item : 'TKey -> 'TValue with get, set
...
nested type Enumerator
nested type KeyCollection
nested type ValueCollection

Full name: System.Collections.Generic.Dictionary<_,_>

--------------------
System.Collections.Generic.Dictionary() : unit
System.Collections.Generic.Dictionary(capacity: int) : unit
System.Collections.Generic.Dictionary(comparer: System.Collections.Generic.IEqualityComparer<'TKey>) : unit
System.Collections.Generic.Dictionary(dictionary: System.Collections.Generic.IDictionary<'TKey,'TValue>) : unit
System.Collections.Generic.Dictionary(capacity: int, comparer: System.Collections.Generic.IEqualityComparer<'TKey>) : unit
System.Collections.Generic.Dictionary(dictionary: System.Collections.Generic.IDictionary<'TKey,'TValue>, comparer: System.Collections.Generic.IEqualityComparer<'TKey>) : unit
val lens : int list
Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
| ( [] )
| ( :: ) of Head: 'T * Tail: 'T list
interface IEnumerable
interface IEnumerable<'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 map : mapping:('T -> 'U) -> list:'T list -> 'U list

Full name: Microsoft.FSharp.Collections.List.map
val length : list:'T list -> int

Full name: Microsoft.FSharp.Collections.List.length
val iter : action:('T -> unit) -> list:'T list -> unit

Full name: Microsoft.FSharp.Collections.List.iter
val i : int
System.Collections.Generic.Dictionary.ContainsKey(key: int) : bool
val sortBy : projection:('T -> 'Key) -> list:'T list -> 'T list (requires comparison)

Full name: Microsoft.FSharp.Collections.List.sortBy
val a : 'a list
property List.Length: int
val test : string list list

Full name: Script.test