Functional wrappers for TryParse APIs

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// see also 
// http://stackoverflow.com/questions/4949941/convert-string-to-system-datetime-in-f

module TryParser =
    // convenient, functional TryParse wrappers returning option<'a>
    let tryParseWith (tryParseFunc: string -> bool * _) = tryParseFunc >> function
        | true, v    -> Some v
        | false, _   -> None

    let parseDate   = tryParseWith System.DateTime.TryParse
    let parseInt    = tryParseWith System.Int32.TryParse
    let parseSingle = tryParseWith System.Single.TryParse >> Option.filter System.Single.IsFinite
    let parseDouble = tryParseWith System.Double.TryParse
    // etc.

    // active patterns for try-parsing strings
    let (|Date|_|)   = parseDate
    let (|Int|_|)    = parseInt
    let (|Single|_|) = parseSingle
    let (|Double|_|) = parseDouble

open TryParser

// tests
let parseMe = function
    | Date d   -> printfn "DateTime %A" d
    | Int 42   -> printfn "Bingo!"
    | Int i    -> printfn "Int32 %i" i
    | Single f -> printfn "Single %g" f
    | Double d -> printfn "Double %g" d
    | s        -> printfn "Don't know how to parse %A" s

parseMe "213"
parseMe "2010-02-22"
parseMe "3,0"
parseMe "jslkdfjlkj"
parseMe "42"
parseMe "3.40282e+39"

val tryParseWith : tryParseFunc:(string -> bool * 'a) -> (string -> 'a option)

val tryParseFunc : (string -> bool * 'a)

Multiple items
val string : value:'T -> string

--------------------
type string = System.String

[<Struct>]
type bool = System.Boolean

val v : 'a

union case Option.Some: Value: 'T -> Option<'T>

union case Option.None: Option<'T>

val parseDate : (string -> System.DateTime option)

namespace System

Multiple items
[<Struct>]
type DateTime =
  new : ticks: int64 -> unit + 13 overloads
  member Add : value: TimeSpan -> DateTime + 1 overload
  member AddDays : value: float -> DateTime
  member AddHours : value: float -> DateTime
  member AddMilliseconds : value: float -> DateTime
  member AddMinutes : value: float -> DateTime
  member AddMonths : months: int -> DateTime
  member AddSeconds : value: float -> DateTime
  member AddTicks : value: int64 -> DateTime
  member AddYears : value: int -> DateTime
  ...

--------------------
System.DateTime ()
   (+0 other overloads)
System.DateTime(ticks: int64) : System.DateTime
   (+0 other overloads)
System.DateTime(ticks: int64, kind: System.DateTimeKind) : System.DateTime
   (+0 other overloads)
System.DateTime(year: int, month: int, day: int) : System.DateTime
   (+0 other overloads)
System.DateTime(year: int, month: int, day: int, calendar: System.Globalization.Calendar) : System.DateTime
   (+0 other overloads)
System.DateTime(year: int, month: int, day: int, hour: int, minute: int, second: int) : System.DateTime
   (+0 other overloads)
System.DateTime(year: int, month: int, day: int, hour: int, minute: int, second: int, kind: System.DateTimeKind) : System.DateTime
   (+0 other overloads)
System.DateTime(year: int, month: int, day: int, hour: int, minute: int, second: int, calendar: System.Globalization.Calendar) : System.DateTime
   (+0 other overloads)
System.DateTime(year: int, month: int, day: int, hour: int, minute: int, second: int, millisecond: int) : System.DateTime
   (+0 other overloads)
System.DateTime(year: int, month: int, day: int, hour: int, minute: int, second: int, millisecond: int, kind: System.DateTimeKind) : System.DateTime
   (+0 other overloads)

System.DateTime.TryParse(s: System.ReadOnlySpan<char>, result: byref<System.DateTime>) : bool
System.DateTime.TryParse(s: string, result: byref<System.DateTime>) : bool
System.DateTime.TryParse(s: System.ReadOnlySpan<char>, provider: System.IFormatProvider, styles: System.Globalization.DateTimeStyles, result: byref<System.DateTime>) : bool
System.DateTime.TryParse(s: string, provider: System.IFormatProvider, styles: System.Globalization.DateTimeStyles, result: byref<System.DateTime>) : bool

val parseInt : (string -> int option)

[<Struct>]
type Int32 =
  member CompareTo : value: obj -> int + 1 overload
  member Equals : obj: obj -> bool + 1 overload
  member GetHashCode : unit -> int
  member GetTypeCode : unit -> TypeCode
  member System.IConvertible.ToBoolean : provider: IFormatProvider -> bool
  member System.IConvertible.ToByte : provider: IFormatProvider -> byte
  member System.IConvertible.ToChar : provider: IFormatProvider -> char
  member System.IConvertible.ToDateTime : provider: IFormatProvider -> DateTime
  member System.IConvertible.ToDecimal : provider: IFormatProvider -> decimal
  member System.IConvertible.ToDouble : provider: IFormatProvider -> float
  ...

System.Int32.TryParse(s: System.ReadOnlySpan<char>, result: byref<int>) : bool
System.Int32.TryParse(s: string, result: byref<int>) : bool
System.Int32.TryParse(s: System.ReadOnlySpan<char>, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<int>) : bool
System.Int32.TryParse(s: string, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<int>) : bool

val parseSingle : (string -> float32 option)

[<Struct>]
type Single =
  member CompareTo : value: obj -> int + 1 overload
  member Equals : obj: obj -> bool + 1 overload
  member GetHashCode : unit -> int
  member GetTypeCode : unit -> TypeCode
  member System.IConvertible.ToBoolean : provider: IFormatProvider -> bool
  member System.IConvertible.ToByte : provider: IFormatProvider -> byte
  member System.IConvertible.ToChar : provider: IFormatProvider -> char
  member System.IConvertible.ToDateTime : provider: IFormatProvider -> DateTime
  member System.IConvertible.ToDecimal : provider: IFormatProvider -> decimal
  member System.IConvertible.ToDouble : provider: IFormatProvider -> float
  ...

System.Single.TryParse(s: System.ReadOnlySpan<char>, result: byref<float32>) : bool
System.Single.TryParse(s: string, result: byref<float32>) : bool
System.Single.TryParse(s: System.ReadOnlySpan<char>, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<float32>) : bool
System.Single.TryParse(s: string, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<float32>) : bool

module Option

from Microsoft.FSharp.Core

val filter : predicate:('T -> bool) -> option:'T option -> 'T option

System.Single.IsFinite(f: float32) : bool

val parseDouble : (string -> float option)

[<Struct>]
type Double =
  member CompareTo : value: obj -> int + 1 overload
  member Equals : obj: obj -> bool + 1 overload
  member GetHashCode : unit -> int
  member GetTypeCode : unit -> TypeCode
  member System.IConvertible.ToBoolean : provider: IFormatProvider -> bool
  member System.IConvertible.ToByte : provider: IFormatProvider -> byte
  member System.IConvertible.ToChar : provider: IFormatProvider -> char
  member System.IConvertible.ToDateTime : provider: IFormatProvider -> DateTime
  member System.IConvertible.ToDecimal : provider: IFormatProvider -> decimal
  member System.IConvertible.ToDouble : provider: IFormatProvider -> float
  ...

System.Double.TryParse(s: System.ReadOnlySpan<char>, result: byref<float>) : bool
System.Double.TryParse(s: string, result: byref<float>) : bool
System.Double.TryParse(s: System.ReadOnlySpan<char>, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<float>) : bool
System.Double.TryParse(s: string, style: System.Globalization.NumberStyles, provider: System.IFormatProvider, result: byref<float>) : bool

module TryParser

from Script

val parseMe : _arg1:string -> unit

active recognizer Date: string -> System.DateTime option

val d : System.DateTime

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

active recognizer Int: string -> int option

val i : int

active recognizer Single: string -> float32 option

val f : float32

active recognizer Double: string -> float option

val d : float

val s : string