5
F＃で興味深い関数を書いています（HaskellのスクラップYour Boilerplateで利用可能なあらゆる関数と同じように）。残念ながら、かなり小さなデータ構造でさえ、スタックオーバーフローを素早く引き起こします。私はどのように私は尾の再帰的なバージョン、継続的なスタイルのバージョンを渡すか、または同等のアルゴリズムに変換することができますかと思っていた。私はF＃がモナドをサポートしていると信じているので、継続モナドはオプションです。このF＃関数がスタックのオーバーフローを引き起こさないようにするにはどうすればいいですか？
// These are used for a 50% speedup
let mutable tupleReaders : List<System.Type * (obj -> obj[])> = []
let mutable unionTagReaders : List<System.Type * (obj -> int)> = []
let mutable unionReaders : List<(System.Type * int) * (obj -> obj[])> = []
let mutable unionCaseInfos : List<System.Type * Microsoft.FSharp.Reflection.UnionCaseInfo[]> = []
let mutable recordReaders : List<System.Type * (obj -> obj[])> = []
(*
Traverses any data structure in a preorder traversal
Calls f, g, h, i, j which determine the mapping of the current node being considered
WARNING: Not able to handle option types
At runtime, option None values are represented as null and so you cannot determine their runtime type.
See http://stackoverflow.com/questions/21855356/dynamically-determine-type-of-option-when-it-has-value-none
http://stackoverflow.com/questions/13366647/how-to-generalize-f-option
*)
open Microsoft.FSharp.Reflection
let map5<'a,'b,'c,'d,'e,'z> (f:'a->'a) (g:'b->'b) (h:'c->'c) (i:'d->'d) (j:'e->'e) (src:'z) =
let ft = typeof<'a>
let gt = typeof<'b>
let ht = typeof<'c>
let it = typeof<'d>
let jt = typeof<'e>
let rec drill (o:obj) : obj =
if o = null then
o
else
let ot = o.GetType()
if FSharpType.IsUnion(ot) then
let tag = match List.tryFind (fst >> ot.Equals) unionTagReaders with
| Some (_, reader) ->
reader o
| None ->
let newReader = FSharpValue.PreComputeUnionTagReader(ot)
unionTagReaders <- (ot, newReader)::unionTagReaders
newReader o
let info = match List.tryFind (fst >> ot.Equals) unionCaseInfos with
| Some (_, caseInfos) ->
Array.get caseInfos tag
| None ->
let newCaseInfos = FSharpType.GetUnionCases(ot)
unionCaseInfos <- (ot, newCaseInfos)::unionCaseInfos
Array.get newCaseInfos tag
let vals = match List.tryFind (fun ((tau, tag'), _) -> ot.Equals tau && tag = tag') unionReaders with
| Some (_, reader) ->
reader o
| None ->
let newReader = FSharpValue.PreComputeUnionReader info
unionReaders <- ((ot, tag), newReader)::unionReaders
newReader o
FSharpValue.MakeUnion(info, Array.map traverse vals)
elif FSharpType.IsTuple(ot) then
let fields = match List.tryFind (fst >> ot.Equals) tupleReaders with
| Some (_, reader) ->
reader o
| None ->
let newReader = FSharpValue.PreComputeTupleReader(ot)
tupleReaders <- (ot, newReader)::tupleReaders
newReader o
FSharpValue.MakeTuple(Array.map traverse fields, ot)
elif FSharpType.IsRecord(ot) then
let fields = match List.tryFind (fst >> ot.Equals) recordReaders with
| Some (_, reader) ->
reader o
| None ->
let newReader = FSharpValue.PreComputeRecordReader(ot)
recordReaders <- (ot, newReader)::recordReaders
newReader o
FSharpValue.MakeRecord(ot, Array.map traverse fields)
else
o
and traverse (o:obj) =
let parent =
if o = null then
o
else
let ot = o.GetType()
if ft = ot || ot.IsSubclassOf(ft) then
f (o :?> 'a) |> box
elif gt = ot || ot.IsSubclassOf(gt) then
g (o :?> 'b) |> box
elif ht = ot || ot.IsSubclassOf(ht) then
h (o :?> 'c) |> box
elif it = ot || ot.IsSubclassOf(it) then
i (o :?> 'd) |> box
elif jt = ot || ot.IsSubclassOf(jt) then
j (o :?> 'e) |> box
else
o
drill parent
traverse src |> unbox : 'z
をあなたは、スタックオーバーフローを行くしている例を与えることはできますか？ –