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  1. open System
  2. open LanguagePrimitives
  3.  
  4. module RoundedCalculation =
  5.   [<Measure>]
  6.   type rounded
  7.   type NotRounded = float
  8.   type Rounded = float<rounded>
  9.  
  10.   let mutable _sigDigs = 0
  11.  
  12.   let inline round x = Math.Round(float x, _sigDigs) |> FloatWithMeasure<rounded>
  13.  
  14.   let (+.) (x:Rounded) (y:Rounded) =
  15.     x + y |> round
  16.   let (-. ) (x:Rounded) (y:Rounded) =
  17.     x - y |> round
  18.   let (/.) (x:Rounded) (y:Rounded) =
  19.     x / y |> round
  20.   let ( *. ) (x:Rounded) (y:Rounded) =
  21.     x * y |> round
  22.  
  23.  
  24.   type RoundingWorkflow() =
  25.     /// NotRounded -> (Rounded->NotRounded) -> NotRounded
  26.     member this.Bind(result : NotRounded, rest : Rounded -> NotRounded) : NotRounded =
  27.       round result
  28.       |> rest 
  29.     /// Rounded -> NotRounded               
  30.     member this.Return (x:Rounded) : NotRounded = float x
  31.  
  32.   let withPrecision sigDigs =
  33.     _sigDigs <- sigDigs 
  34.     new RoundingWorkflow()
  35.  
  36. open RoundedCalculation
  37.  
  38. let rest : float = 
  39.   withPrecision 3 {
  40.     let! x = 1.005
  41.     let! y = 2.004
  42.     let xPlusY = x +. y
  43.     let! a = 1.994
  44.     let! b = 0.995
  45.     let aMinusB = a -. b
  46.     let z = xPlusY *. aMinusB
  47.     return z
  48.   }
  49.  
  50. printfn "%f" rest
  51. // 3.006000
Success #stdin #stdout 0.11s 12000KB
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3.006000
https://ideone.com/GfdYT
language:
F# (mono 4.1)
created:
14 years ago
visibility:
public

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