open System

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//Source 1: http://msdn.microsoft.com/en-us/library/dd233243.aspx

//Source 2: http://rosettacode.org/wiki/Temperature_conversion#F.23

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[<Measure>] type degC // temperature, Celsius/Centigrade

[<Measure>] type degF // temperature, Fahrenheit 

[<Measure>] type degK // temperature, Kelvin

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//------------------

//Conversion methods

let convertCtoF ( temp: float<degC> ) = (9.0 / 5.0 * (float temp) + 32.0) * 1.0<degF>

let convertCtoK ( temp: float<degC> ) = (float temp + 273.15) * 1.0<degK>

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let convertFtoC ( temp: float<degF> ) = 5.0 / 9.0 * (float temp - 32.0) * 1.0<degC>

let convertFtoK ( temp: float<degF> ) = convertCtoK (convertFtoC (temp))

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let convertKtoC ( temp : float<degK>) = (float temp - 273.15)  * 1.0<degC>

let convertKtoF ( temp : float<degK>) = convertCtoF (convertKtoC (temp)) 

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// Define conversion functions from dimensionless floating point values. 

let degreesFahrenheit temp = temp * 1.0<degF>

let degreesCelsius temp = temp * 1.0<degC>

let degreesKelvin temp = temp * 1.0<degK>

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//--------------------

//Displaying conversion results

let doConversion (suffix:char, inputDegrees:float) =

  //let inputDegreesMeasure= inputDegrees * (1.0<degC/degF>)

  match suffix with

  | 'C' -> 

      printfn "%8.2fF" ((convertCtoF (degreesCelsius inputDegrees))/(1.0<degF>))

      printfn "%8.2fK" ((convertCtoK (degreesCelsius inputDegrees))/(1.0<degK>))

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  | 'F' -> 

      printfn "%8.2fC" ((convertFtoC (degreesFahrenheit inputDegrees))/(1.0<degC>))

      printfn "%8.2fK" ((convertFtoK (degreesFahrenheit inputDegrees))/(1.0<degK>))

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  | 'K' -> 

      printfn "%8.2fC" ((convertKtoC (degreesKelvin inputDegrees))/(1.0<degC>))

      printfn "%8.2fF" ((convertKtoF (degreesKelvin inputDegrees))/(1.0<degF>))

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  | _ -> 

      printfn "Suffix is not valid"

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//---------------------

// Console input and handling invalid input

while true do

  printfn "Enter a temperature in degrees followed by (C, F, K):"

  let input = System.Console.ReadLine()

  let mutable inputDegrees = 0.

  if not (String.IsNullOrWhiteSpace(input)) then

    let suffix = input.[input.Length-1]

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    let tryParse = System.Double.TryParse(input.Remove(input.Length-1), &inputDegrees)

    if tryParse then

      doConversion(suffix, inputDegrees)

    else

      printfn "Degrees value is not valid"

  else

    printfn "Suffix is not valid"

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