Как конвертировать из записи в кортеж? - PullRequest
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Как конвертировать из записи в кортеж?

0 голосов
/ 31 мая 2018

Я довольно часто использую провайдер типа CSV, который использует кортежи для всех базовых данных.Моя проблема в том, что я сталкиваюсь с CSV-файлами с большим количеством столбцов и считаю, что построение инфраструктуры на основе манипулирования данными такого размера довольно громоздко.Как мне создать функцию, которая будет обновлять только определенное подмножество столбцов, не создавая огромных операторов сопоставления с образцом?См. Пример кода ниже. 

// I want to generate lots of sample data for the first three columns
// And I would like to avoid creating giant record types in order to
// do this task as the csv's are always changing and the records would
// have to change as well
type CumbersomeCSVRow = // 17 fields now, but imagine 212
    string * string * string * Option<int> * string * 
    Option<int> * string * string * string * string * 
    string * string * Option<float> * string * 
    Option<float> * Option<float> * string

// Here is a sample row of data
let sampleCumbersomeRow : CumbersomeCSVRow = 
    ("First","Second","Third",Some(52),"MSCI",None,"B74A123","",
     "Airlines","Transportation","","",Some(1.04293),"Updated",
     Some(0.95),Some(56.7423),"Measured")

// Record type of the sample data that I want to 'insert' into the cumbersome data type
type FirstThreeStrings = 
    { First : string; Second : string; Third : string}

// and some instances of the new data
let generatedFrontMatters = 
    // imagine lots of sample data and workflows to create it, hence the records
    seq { for letter in ["A";"B";"C"] -> 
            { First  = letter;
              Second = letter + letter
              Third  = letter + letter + letter } }

1 Ответ

0 голосов
/ 31 мая 2018

Взгляните на FSharp.Reflection модуль 

// Your Code --------------------------------------------------

// I want to generate lots of sample data for the first three columns
// And I would like to avoid creating giant record types in order to
// do this task as the csv's are always changing and the records would
// have to change as well
type CumbersomeCSVRow = // 17 fields now, but imagine 212
    string * string * string * Option<int> * string * 
    Option<int> * string * string * string * string * 
    string * string * Option<float> * string * 
    Option<float> * Option<float> * string

// Here is a sample row of data
let sampleCumbersomeRow : CumbersomeCSVRow = 
    ("First","Second","Third",Some(52),"MSCI",None,"B74A123","",
     "Airlines","Transportation","","",Some(1.04293),"Updated",
     Some(0.95),Some(56.7423),"Measured")

// Record type of the sample data that I want to 'insert' into the cumbersome data type
type FirstThreeStrings = 
    { First : string; Second : string; Third : string}

// and some instances of the new data
let generatedFrontMatters = 
    // imagine lots of sample data and workflows to create it, hence the records
    seq { for letter in ["A";"B";"C"] -> 
            { First  = letter;
              Second = letter + letter
              Third  = letter + letter + letter } }

// Response ---------------------------------------------------

open FSharp.Reflection

// create a static back matter to append to
// the slicing here is the part that will need to change as the data changes
//      ++ maybe there's a better way to handle this part??
let staticBackMatter = 
    sampleCumbersomeRow
    |> FSharpValue.GetTupleFields
    |> (fun x -> x.[3 .. 16])

// cast the front matter using FSharp.Reflection
let castedFrontMatters = Seq.map FSharpValue.GetRecordFields generatedFrontMatters

// append the data arrays together, create a tuple using reflection, and downcast the result
// to your type
let generatedRows = 
    castedFrontMatters
    |> Seq.map (fun frontArray -> Array.append frontArray staticBackMatter)
    |> Seq.map (fun data -> FSharpValue.MakeTuple(data,typeof<CumbersomeCSVRow>) :?> CumbersomeCSVRow)
    |> Seq.toList

Является ли это правильным F #, я не знаю.

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