Progressive tax calculator

Calculates progressive tax on an annual income.

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/// Calculates progressive tax on an annual income
let calcProgressiveTax taxBrackets income =
  taxBrackets @ [ (System.Double.MaxValue, 0.0) ]
  |> Seq.windowed 2
  |> Seq.fold
       (fun (incomeLeft, tax) x ->
         let bracketLow, rate = x.[0]
         let bracketHight = fst x.[1]
         let bracketW = bracketHight - bracketLow
         match incomeLeft, incomeLeft <= bracketW with
         | 0.0, _            -> (0.0, tax)
         | incomeLeft, true  -> (0.0, incomeLeft * rate + tax)
         | incomeLeft, false -> (incomeLeft - bracketW, bracketW * rate + tax)
       )
       (income, 0.0)
  |> snd


// Example
let incomeTaxBelgium2016 =  //   Taxable Income    Tax Rate on 
  [                         //   Bracket, EUR      Income in Bracket
  (    0.00, 0.25);         //      0 .. 10,860      25%
  (10860.00, 0.30);         // 10,860 .. 12,470      30%
  (12470.00, 0.40);         // 12,470 .. 20,780      40%
  (20780.00, 0.45);         // 20,780 .. 38,080      45%
  (38080.00, 0.50);         // 38,080 ..  over       50%
  ]
  
calcProgressiveTax incomeTaxBelgium2016 100000.00
// Returns: 45,267.00

val calcProgressiveTax : taxBrackets:(float * float) list -> income:float -> float

Full name: Script.calcProgressiveTax

Calculates progressive tax on an annual income

val taxBrackets : (float * float) list

val income : float

namespace System

type Double =
  struct
    member CompareTo : value:obj -> int + 1 overload
    member Equals : obj:obj -> bool + 1 overload
    member GetHashCode : unit -> int
    member GetTypeCode : unit -> TypeCode
    member ToString : unit -> string + 3 overloads
    static val MinValue : float
    static val MaxValue : float
    static val Epsilon : float
    static val NegativeInfinity : float
    static val PositiveInfinity : float
    ...
  end

Full name: System.Double

field float.MaxValue = 1.79769313486e+308

module Seq

from Microsoft.FSharp.Collections

val windowed : windowSize:int -> source:seq<'T> -> seq<'T []>

Full name: Microsoft.FSharp.Collections.Seq.windowed

val fold : folder:('State -> 'T -> 'State) -> state:'State -> source:seq<'T> -> 'State

Full name: Microsoft.FSharp.Collections.Seq.fold

val incomeLeft : float

val tax : float

val x : (float * float) []

val bracketLow : float

val rate : float

val bracketHight : float

val fst : tuple:('T1 * 'T2) -> 'T1

Full name: Microsoft.FSharp.Core.Operators.fst

val bracketW : float

val snd : tuple:('T1 * 'T2) -> 'T2

Full name: Microsoft.FSharp.Core.Operators.snd

val incomeTaxBelgium2016 : (float * float) list

Full name: Script.incomeTaxBelgium2016

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More information

Link:	http://fssnip.net/7PY
Posted:	3 years ago
Author:	Ujjawal Sinha
Tags:	finance , tax