if-your-fsharp-code-compiles-it-usually-works

CallingHasFever.fs

hasFever (Celsius 10.5)
hasFever (Fahrenheit 22.5)

CompilerError.fs

let hasFever temperature =
  match temperature with 
  | Celsius value -> (value > 37.5)

Declaration.fs

let tempInCelsius = Celsius 10.8
let tempInFahernheit = Fahrenheit 10.6

HasFever.fs

let hasFever temperature =
  match temperature with 
  | Celsius value -> (value > 37.5)
  | Fahrenheit value -> (value > 99.0)

Temperature.cs

public abstract class Temperature 
{
  public double Value { get; private set; }

  protected Temperature(double value) 
  {
    Value = value;
  }
}

public class Celsius : Temperature
{
  public Celsius (double value) : base(value)
  {

  }
}

public class Fahrenheit : Temperature
{
  public Fahrenheit (double value) : base(value)
  {
    
  }
} 

public class Program 
{
  public static void Main() 
  {
    Temperature tempInCelsius = new Celsius(10.8);
    Temperature tempInFahernheit = new Fahrenheit(10.6);
  }  
}

Temperature.fs

type Temperature = 
  | Celsius of double
  | Fahrenheit of double