DouKaku? 2114 iwk: nskj77さんのコードを参考に修正して...(与えた条件を満たす候補)

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This comment is reply for 2109 iwk: イマイチ。(与えた条件を満たす候補). Go to thread root.

nskj77さんのコードを参考に修正してみました。

see:

#light
type ListBuilder () =
    member l.Bind (v,f) = List.concat (List.map f v)
    member l.Return x = [x]
    member l.Let(v,f) = f v

let guard c = if c then [()] else []

let doList = new ListBuilder()

let rec satisfy prev bs cmds =
    match bs, cmds with
    | b::[], _     -> prev b
    | b::bs, cmd::cmds ->
            match cmd with
            | "not" -> satisfy prev ((not b)::bs) cmds
            | "and" -> satisfy ((&&) (prev b)) bs cmds
            | "or"  -> satisfy ((||) (prev b)) bs cmds

let rec all_comb = function
    | 0 -> [[]]
    | n -> doList { let! rest = all_comb (n-1)
                    let! result = [(true::rest);(false::rest)]
                    return result }

let get_combs cmds =
    let len = 1 + (List.length (List.filter ((<>) "not") cmds))
    doList { let! bs = all_comb len
             do! guard (satisfy (fun x -> x) bs cmds)
             return bs }

do get_combs ["and";"or";"not";"and"]
   |> (print_any >> print_newline)

さらにモナドを使わずに書き直してみました。

#light
let rec satisfy prev bs cmds =
    match bs, cmds with
    | b::[], _     -> prev b
    | b::bs, cmd::cmds ->
            match cmd with
            | "not" -> satisfy prev ((not b)::bs) cmds
            | "and" -> satisfy ((&&) (prev b)) bs cmds
            | "or"  -> satisfy ((||) (prev b)) bs cmds

let rec all_comb = function
    | 0 -> [[]]
    | n -> [ for res in all_comb (n-1) ->> [true::res;false::res] ]

let get_combs cmds =
    let len = 1 + (List.length (List.filter ((<>) "not") cmds))
    [for bs in all_comb len when satisfy (fun x -> x) bs cmds -> bs]

do get_combs ["and";"or";"not";"and"]
   |> (print_any >> print_newline)

DouKaku?

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