private static FSharpChoice <int, Errors> Positive(int a)
{
if (a <= 0)
{
return(FSharpChoice.Error <int>("Field must be positive"));
}
return(FSharpChoice.Ok(a));
}
/// <summary>
/// Same as FSharpChoice.Validator, for demo purposes only
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="pred"></param>
/// <param name="err"></param>
/// <returns></returns>
static Func <T, FSharpChoice <T, Errors> > Validator <T>(Predicate <T> pred, string err)
{
return(x => {
if (pred(x))
{
return FSharpChoice.Ok(x);
}
return FSharpChoice.Error <T>(err);
});
}
static FSharpChoice <T, Errors> GreaterThan <T>(T value, T other, string err) where T : IComparable <T>
{
var valueNull = Equals(null, value);
var otherNull = Equals(null, other);
if (valueNull && otherNull || valueNull != otherNull || value.CompareTo(other) > 0)
{
return(FSharpChoice.Ok(value));
}
return(FSharpChoice.Error <T>(err));
}
public void Part1()
{
var costDave = ClubbedToDeath.CostToEnter(Dave);
Assert.AreEqual(FSharpChoice.Error <decimal>("Too old!"), costDave);
var costKen = ClubbedToDeath.CostToEnter(Ken);
Assert.AreEqual(FSharpChoice.Ok(5m), costKen);
var costRuby = ClubbedToDeath.CostToEnter(Ruby);
Assert.AreEqual(FSharpChoice.Ok(0m), costRuby);
var Ruby17 = new Person(
age: 17,
clothes: Ruby.Clothes,
sobriety: Ruby.Sobriety,
gender: Ruby.Gender);
var costRuby17 = ClubbedToDeath.CostToEnter(Ruby17);
Assert.AreEqual(FSharpChoice.Error <decimal>("Too young!"), costRuby17);
var KenUnconscious = new Person(
age: Ken.Age,
clothes: Ken.Clothes,
gender: Ken.Gender,
sobriety: Sobriety.Unconscious);
var costKenUnconscious = ClubbedToDeath.CostToEnter(KenUnconscious);
Assert.AreEqual(FSharpChoice.Error <decimal>("Sober up!"), costKenUnconscious);
/**
* The thing to note here is how the Validations can be composed together in a computation expression.
* The type system is making sure that failures flow through your computation in a safe manner.
*/
}