F#文档是否有办法按类型搜索函数？

Question

假设我想知道F#是否具有类型的库函数

('T -> bool) -> 'T list -> int

即,计算函数返回的列表中有多少项的内容.(或返回返回true的第一个项的索引)

在MSDN上的文档准备就绪之前,我曾经在MSR站点上使用F#的大列表.我可以在页面上搜索上面的文本,因为列出了类型.但是现在MSDN文档只列出了各个页面上的类型 - 模块页面是一个描述性文本.谷歌有点排序,但它无济于事

// compatible interfaces
('T -> bool) -> Seq<'T> -> int
// argument-swaps
Seq<'T> -> ('T -> bool) -> int
// type-variable names
('a -> bool) -> Seq<'a> -> int
// wrappers
('a -> bool) -> 'a list -> option<int>
// uncurried versions
('T -> bool) * 'T list -> int
// .NET generic syntax
('T -> bool) -> List<'T> -> int
// methods
List<'T> member : ('T -> bool) -> int

Haskell有一个名为Hoogle的独立程序.F#是否具有等价物,如Fing或其他东西？

Answer 1

我不知道任何这样的工具.但是,使用System.Reflection(甚至更好的,PowerPack中的元数据库)编写一个可能是一个有趣的练习,因此您可以考虑等价模数型变量名等.

编辑 - 我是对的 - 这是一个有趣的练习.接下来会有很多瑕疵,但对于〜150行代码来说并不算太糟糕.希望这足以让有人开始想要使用真正的工具.它没有像检查具有重新排序参数的函数那样做任何高级操作,并且元数据库对于使用完全限定名称有点挑剔,因此您需要小心一点.为了回答原帖中的问题,我执行了

find "('a -> Microsoft.FSharp.Core.bool) -> Microsoft.FSharp.Collections.list`1<'a> -> Microsoft.FSharp.Core.int" 

并得到以下候选人名单:

Microsoft.FSharp.Core.Operators.( + )
Microsoft.FSharp.Core.Operators.( - )
Microsoft.FSharp.Core.Operators.( * )
Microsoft.FSharp.Core.Operators.( / )
Microsoft.FSharp.Core.Operators.( % )
Microsoft.FSharp.Core.Operators.sqrt
Microsoft.FSharp.Core.LanguagePrimitives.EnumOfValue
Microsoft.FSharp.Core.LanguagePrimitives.EnumToValue
Microsoft.FSharp.Core.LanguagePrimitives.AdditionDynamic
Microsoft.FSharp.Core.LanguagePrimitives.CheckedAdditionDynamic
Microsoft.FSharp.Core.LanguagePrimitives.MultiplyDynamic
Microsoft.FSharp.Core.LanguagePrimitives.CheckedMultiplyDynamic
Microsoft.FSharp.Core.LanguagePrimitives.GenericZero
Microsoft.FSharp.Core.LanguagePrimitives.GenericOne
Microsoft.FSharp.Collections.List.find
Microsoft.FSharp.Collections.List.findIndex
Microsoft.FSharp.Collections.List.maxBy
Microsoft.FSharp.Collections.List.minBy

其中,只有List.findIndex拥有正是你要找的泛型类型,但类型参数的正确组合,这样做对别人(例如,如果'a = int再List.find有需要的类型).不幸的是,在搜索中没有考虑约束,因此非List函数实际上不能匹配.

不用多说,这里是我使用的代码 - 您需要添加对FSharp.PowerPack.Metadata程序集的引用以使其工作.

open Microsoft.FSharp.Metadata
open System.Text.RegularExpressions

(* type parameters let us switch out representation if need be *)
type Tag<'ty> = | Tuple | Arr | Ground of 'ty
type Ty<'ty,'a> = Param of 'a | Complex of Tag<'ty> * Ty<'ty,'a> list

(* Gets something stable from an FSharpEntity so that we can see if two are identical *)
let rec getType (e:FSharpEntity) =
  if (e.IsAbbreviation) then
    getType e.AbbreviatedType.NamedEntity
  else
    e.ReflectionType

(* FSharpType -> Ty<System.Type,string> *)
let rec cvt (e:FSharpType) =
  if e.IsTuple then
    Complex(Tuple, e.GenericArguments |> Seq.map cvt |> List.ofSeq)
  elif e.IsFunction then
    Complex(Arr, e.GenericArguments |> Seq.map cvt |> List.ofSeq)
  elif e.IsGenericParameter then
    Param e.GenericParameter.Name
  else
    Complex(Ground(e.NamedEntity |> getType), e.GenericArguments |> Seq.map cvt |> List.ofSeq)

(* substitute type for variable within another type *)
let rec subst v t = function
| Complex(tag,l) -> Complex(tag, l |> List.map (subst v t))
| Param i when i = v -> t
| Param j -> Param j

(* get type variables used in a type *)
let rec usedVars = function
| Param i -> Set.singleton i
| Complex(tag, l) -> Set.unionMany (List.map usedVars l)

(* Find most general unifier (if any) for two types *)
let mgu t1 t2 =
  let rec mgu subs = function
  | [] -> Some subs
  | (Complex(tag1,l1),Complex(tag2,l2))::rest ->
       if tag1 <> tag2 then
         None
       else
         let rec loop r = function
         | [],[] -> mgu subs r
         | [],_ | _,[] -> None
         | x::xs, y::ys -> loop ((x,y)::r) (xs,ys)
         loop rest (l1,l2)
  | (Param i, Param j)::rest when i = j -> mgu subs rest
  | ((Param i, x) | (x, Param i))::rest ->
       if (Set.contains i (usedVars x)) then
         None (* type would be infinite when unifying *)
       else
         mgu ((i,x)::subs) (rest |> List.map (fun (t1,t2) -> (subst i x t1, subst i x t2)))
  mgu [] [t1,t2]

(* Active patterns for parsing - this is ugly... *)
let (|StartsWith|_|) r s =
  let m = Regex.Match(s, r)
  if m.Success && m.Index = 0 then
    Some(m.Value, s.Substring(m.Length))
  else None

let rec (|Any|) (|P|_|) = function
| P(x,Any (|P|_|) (l,r)) -> x::l, r
| s -> [],s

let rec (|Any1|_|) (|P|_|) = function
| P(x,Any (|P|_|) (l,r)) -> Some(x::l, r)
| _ -> None

let (|Seq|_|) (|P|_|) (|Q|_|) = function
| P(x,Q(y,r)) -> Some((x,y),r)
| _ -> None

let (|Choice|_|) (|P|_|) (|Q|_|) = function
| P(p) -> Some p
| Q(p) -> Some p
| _ -> None

let (|Delimit|_|) s (|P|_|) = function
| P(x,Any ((|Seq|_|) ((|StartsWith|_|) s) (|P|_|)) (l,r)) -> Some(x::(List.map snd l), r)
| _ -> None

let (|Delimit1|_|) s (|P|_|) = function
| P(x,StartsWith s (_,Delimit s (|P|_|) (l,r))) -> Some(x::l, r)
| _ -> None

(* Basically a BNF grammar for types *)
let rec (|TyE|_|) = function
| ArrE(p) | TupleE(p) | AtomE(p) -> Some(p)
| _ -> None
and (|ArrE|_|) = function
| Choice (|TupleE|_|) (|AtomE|_|) (dom,StartsWith "->" (_,TyE(rng,r))) -> Some(Complex(Arr,[dom;rng]), r)
| _ -> None
and (|TupleE|_|) = function
| Delimit1 @"\*" (|AtomE|_|) (l,r) -> Some(Complex(Tuple,l), r)
| _ -> None
and (|AtomE|_|) = function
| ParamE(x,r) | GroundE(x,r) | StartsWith @"\(" (_,TyE(x,StartsWith @"\)" (_,r))) -> Some(x,r)
| _ -> None
and (|ParamE|_|) = function
| StartsWith "'[a-zA-Z0-9]+" (s,r) -> Some(Param s, r)
| _ -> None
and (|GroundE|_|) = function
| StartsWith "[`.a-zA-Z0-9]+" (gnd, StartsWith "<" (_, Delimit "," (|TyE|_|) (l, StartsWith ">" (_,r)))) -> 
      let ty = FSharpAssembly.FSharpLibrary.GetEntity gnd |> getType
      Some(Complex(Ground(ty), l), r)
| StartsWith "[`.a-zA-Z0-9]+" (gnd, r) ->
      let ty = FSharpAssembly.FSharpLibrary.GetEntity gnd |> getType
      Some(Complex(Ground(ty), []), r)
| _ -> None

(* parse a string into a type *)
let parse (s:string) =
  (* remove whitespace before matching *)
  match s.Replace(" ","") with
  | TyE(ty,"") -> ty
  | _ -> failwith "Not a well-formed type"

(* an infinite stream of possible variable names - for performing renaming *)
let rec names = 
  let letters = ['a' .. 'z'] |> List.map string
  seq {
    yield! letters
    for n in names do
      for l in letters do
        yield n + l
  }

(* finds entities in the F# library with the requested signature, modulo type parameter unification *)
let find s =
  let ty = parse s
  let vars = usedVars ty
  seq {
    for e in FSharpAssembly.FSharpLibrary.Entities do
    for m in e.MembersOrValues do
      (* need try/catch to avoid error on weird types like "[]`1" *)
      match (try Some(cvt m.Type) with _ -> None) with
      | Some ty2 ->
        (* rename all type variables from the query to avoid incorrectly unifying with type variables in signatures *)
        let used = usedVars ty2
        let newVars = Seq.choose (fun v -> if Set.contains v used then None else Some(Param v)) names
        let varMap = Map.ofSeq (Seq.zip vars newVars)
        let ty = Map.fold (fun t v p -> subst v p t) ty varMap
        match mgu ty ty2 with
        | None -> ()
        | Some _ -> yield sprintf "%s.%s.%s" e.Namespace e.DisplayName m.DisplayName 
      | _ -> () }

Answer 2

基于kvb的答案,我创建了一个完整的应用程序.它在github上托管,网址为http://github.com/sandersn/fing.

代码仍然非常难看,但它适用于简单的情况.我现在拿出了kvb最通用的unifier(mgu),因为它增加了许多非显而易见的结果.像结构约束和大多数通用超类型这样的花哨的东西也不起作用.

如果您不想从源代码构建,也可以使用命令行版本的二进制文件.(但它仍然需要安装现代版本的.NET运行时.)最后,我会找到一些ASP.NET托管,学习ASP,并将整个内容包装在Web应用程序中,这样就根本不需要安装.(我想如果有需求我可以创建一个客户端GUI,但我对这种事情的经验更少.)

Answer 3

这是最新最好的:http://fsdn.azurewebsites.net/

来自文档:https://github.com/fsdn-projects/FSDN

支持的API签名

API signature                     Query example
Functions and values in modules   int -> string
Fields of records and structs     Ref<'a> => 'a
Methods and properties            'a list -> int or 'a list => int
Constructors                      string -> Uri
Names (function and method names) head : 'a list -> 'a
Active patterns                   (||) : ... -> Expr -> ?