Seq.map error when sending a record in f#

Question

I'm trying to read a File, employees.txt and output a payroll.txt File. The employee file has the following text: H|1111|Jane Doe|8.50|40.0 S|2222|John Doe|0.10|1500.00 . I'm trying to read this file and output the same employees but with salary evaluate already. The thing is that I don't understand very well the logic behind File.ReadLines "employees.txt" |> Seq.map inputline_to_employee |> Seq.map employee_to_outputline Here's the code

open System 
open System.IO 

type Employee =
    | HourlyEmployee of 
        id: string * name: string * pay_rate: float * hours_worked: float
    | SalesEmployee of 
        id: string * name: string * comm_rate: float * sales_amount: float

// inputline_to_student : string -> Student
// Returns a student record for the given input line.
let inputline_to_employee (line : string) =
   let fields = line.Split '|'

   [
       if (fields.[0] = "H") then HourlyEmployee(fields.[1], (fields.[2] + " " + fields.[3]), float fields.[4], float fields.[5])
       else SalesEmployee(fields.[1], (fields.[2] + " " + fields.[3]), float fields.[4], float fields.[5])
   ]

let payroll = function
    | HourlyEmployee (_, _, pay, hrs) -> if (hrs <= 40.) then pay * hrs
                                            else pay * 40. + (hrs * 1.5 * pay)
    | SalesEmployee (_, _, comm, amt) -> comm * amt

// employee_to_outputline : Employee -> string
// Returns the output line for the given employee.
let employee_to_outputline emp =
   let pay = payroll emp 
   match emp with
   | HourlyEmployee (id, name, _, _) ->
        sprintf "%s|%s|%.1f" id name pay
   | SalesEmployee (id, name, _, _) ->
       sprintf "%s|%s|%.1f" id name pay

// main: string [] -> int
// Entry point of the program.
[<EntryPoint>]
let main _ =
   let mutable exit_code = 0
   try
       let wages = 
           File.ReadLines "employees.txt"
               |> Seq.map inputline_to_employee 
               |> Seq.map employee_to_outputline

       File.WriteAllLines ("payroll.txt", wages)

       Console.WriteLine "All employees were read and evaluations were written."
   with
       :? FileNotFoundException as e ->
           Console.Error.WriteLine ("Error: {0}", e.Message)
           exit_code <- 1
   exit_code 

The issue that I'm having is this

The business logic works because I ran it using an array of Employees, but for some reason I can't get this reading the file instead. I know is something about the Seq.map that I'm passing to the functions. BUt I'm relatively new to this language.

Answer 1

inputline_to_employee is returning a list via []. It should instead return the single employee rather than a list with only one entry.

    let inputline_to_employee (line : string) =
    let fields = line.Split '|'
       if (fields.[0] = "H") then HourlyEmployee(fields.[1], (fields.[2] + " " + fields.[3]), float fields.[4], float fields.[5])
       else SalesEmployee(fields.[1], (fields.[2] + " " + fields.[3]), float fields.[4], float fields.[5])