Parsing string expressions, the lazy way

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let eval = 
    let dt = new System.Data.DataTable()
    fun expr -> System.Convert.ToDouble(dt.Compute(expr,""))

// usage (FSI)          
// > eval "(1+5)*7/((3+(2-1))/(7-3))";;
// val it : float = 42.0

val eval : (string -> float)

Full name: Script.eval

val dt : System.Data.DataTable

namespace System

namespace System.Data

Multiple items
type DataTable =
  inherit MarshalByValueComponent
  new : unit -> DataTable + 2 overloads
  member AcceptChanges : unit -> unit
  member BeginInit : unit -> unit
  member BeginLoadData : unit -> unit
  member CaseSensitive : bool with get, set
  member ChildRelations : DataRelationCollection
  member Clear : unit -> unit
  member Clone : unit -> DataTable
  member Columns : DataColumnCollection
  member Compute : expression:string * filter:string -> obj
  ...

Full name: System.Data.DataTable

--------------------
System.Data.DataTable() : unit
System.Data.DataTable(tableName: string) : unit
System.Data.DataTable(tableName: string, tableNamespace: string) : unit

val expr : string

type Convert =
  static val DBNull : obj
  static member ChangeType : value:obj * typeCode:TypeCode -> obj + 3 overloads
  static member FromBase64CharArray : inArray:char[] * offset:int * length:int -> byte[]
  static member FromBase64String : s:string -> byte[]
  static member GetTypeCode : value:obj -> TypeCode
  static member IsDBNull : value:obj -> bool
  static member ToBase64CharArray : inArray:byte[] * offsetIn:int * length:int * outArray:char[] * offsetOut:int -> int + 1 overload
  static member ToBase64String : inArray:byte[] -> string + 3 overloads
  static member ToBoolean : value:obj -> bool + 17 overloads
  static member ToByte : value:obj -> byte + 18 overloads
  ...

Full name: System.Convert

System.Convert.ToDouble(value: System.DateTime) : float
   (+0 other overloads)
System.Convert.ToDouble(value: bool) : float
   (+0 other overloads)
System.Convert.ToDouble(value: string) : float
   (+0 other overloads)
System.Convert.ToDouble(value: decimal) : float
   (+0 other overloads)
System.Convert.ToDouble(value: float) : float
   (+0 other overloads)
System.Convert.ToDouble(value: float32) : float
   (+0 other overloads)
System.Convert.ToDouble(value: uint64) : float
   (+0 other overloads)
System.Convert.ToDouble(value: int64) : float
   (+0 other overloads)
System.Convert.ToDouble(value: uint32) : float
   (+0 other overloads)
System.Convert.ToDouble(value: int) : float
   (+0 other overloads)

System.Data.DataTable.Compute(expression: string, filter: string) : obj