F# Sorting Sequence of Records where Value isn't yet assigned to Type in Sequence

问题

I am trying to sort a Sequence of records by the second element in each record. The problem is that these are not a value and instead are just a Type. I have a function where it returns the value based on which Type it is.

This is what I have:

type Suit = Spades | Clubs | Hearts | Diamonds
type Rank = Ace | Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Jack | Queen | King
type Card = { suit: Suit; rank: Rank}

type Hand = Card seq

let cardValue(card:Card) = 
    if (card.rank = Ace) then 1
    elif (card.rank = Two) then 2
    elif (card.rank = Three) then 3
    elif (card.rank = Four) then 4
    elif (card.rank = Five) then 5
    elif (card.rank = Six) then 6
    elif (card.rank = Seven) then 7
    elif (card.rank = Eight) then 8
    elif (card.rank = Nine) then 9
    elif (card.rank = Ten) then 10
    elif (card.rank = Jack) then 10
    elif (card.rank = Queen) then 10
    elif (card.rank = King) then 10
    else 0

let sortHandByValue(hand:Hand) = 
......missing code here......

and what I am trying to do is sort Hand by the Rank as a value.

So for example Hand is currently : {{Hearts; Three}; {Spades; Jack}; {Diamonds; Two}}

It will sort Hand so the result is : {{Diamonds; Two}; {Hearts; Three}; {Spades; Jack}}

I tried doing hand |> Seq.sort |>Seq.groupBy id |> Seq.map snd but that doesn't sort it by value and only by alphabetical.

I cannot change any of the types, but I can change everything else. Any ideas would be appreciated, thanks!

回答1:

You need to clean up the code a bit as it shows records, I rewrote the Card type to be a tuple and the match function as well. Then all you needs is to pipe into Seq.sortBy or Seq.sortByDescending (as sortby sorts ascending):

type Suit = Spades | Clubs | Hearts | Diamonds
type Rank = Ace | Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Jack | Queen | King
type Card = Suit * Rank

type Hand = Card seq

let cardValue (card:Card) = 
    match card with 
    | _, Ace -> 1
    | _, Two -> 2
    | _, Three -> 3
    | _, Four -> 4
    | _, Five -> 5
    | _, Six -> 6
    | _, Seven -> 7
    | _, Eight -> 8
    | _, Nine -> 9
    | _, Ten | _, Jack | _, Queen | _, King -> 10


let hand = seq [(Hearts, Three); (Spades, Jack); (Diamonds, Two)]

hand |> Seq.sortBy cardValue 
//val it : seq<Suit * Rank> =
//seq [(Diamonds, Two); (Hearts, Three); (Spades, Jack)]

Version with records: I kept this close to your original.

/// Version with Records
type Suit = Spades | Clubs | Hearts | Diamonds
type Rank = Ace | Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Jack | Queen | King
type Card = { suit: Suit; rank: Rank}
type Hand = seq<Card>

let cardValue(card:Card) = 
    if (card.rank = Ace) then 1
    elif (card.rank = Two) then 2
    elif (card.rank = Three) then 3
    elif (card.rank = Four) then 4
    elif (card.rank = Five) then 5
    elif (card.rank = Six) then 6
    elif (card.rank = Seven) then 7
    elif (card.rank = Eight) then 8
    elif (card.rank = Nine) then 9
    elif (card.rank = Ten) then 10
    elif (card.rank = Jack) then 10
    elif (card.rank = Queen) then 10
    elif (card.rank = King) then 10
    else 0

let hand = seq [{suit=Hearts; rank=Three}; {suit=Spades;rank=Jack}; {suit=Diamonds;rank= Two}]

hand |> Seq.sortBy cardValue

val it : seq = seq [{suit = Diamonds; rank = Two;}; {suit = Hearts; rank = Three;}; {suit = Spades; rank = Jack;}]

来源：https://stackoverflow.com/questions/43448162/f-sorting-sequence-of-records-where-value-isnt-yet-assigned-to-type-in-sequenc

标签

sorting

Sequence

records