/*
* The only thing left is to define the implementation for
* `IArbitrary<Command>`. We register it in the static constructor. We can
* use the `Arbitrary<T>` wrapper class as a helper.
*/
static Command()
{
Arbitrary.Register(new Arbitrary <Command> (
/*
* The generator consist of two branches. We will use the `OneOf`
* combinator to first randomly chooses whether we push a digit
* button or an operator button.
*/
Gen.OneOf(
/*
* If the digit button is selected, then we choose a random
* number from the range of 0 to 9, and create a `Digit`
* command for the chosen number.
*/
from i in Gen.ChooseInt(0, 10)
select Digit(i),
/*
* If the winner was the other branch, then we choose a random
* command from the set of operators.
*/
Gen.ChooseFrom(Add, Subtract, Multiply, Divide, Equals)
),
/*
* How to implement shrinking is a bit harder to figure out.
* Shrinking of operators is not something we can easily define,
* so we will be content with shrinking just the digit command
* utilizing the shrinking defined for integers. We achieve the
* true power of shrinking by reducing the lists of commands to
* shorter examples when LinqCheck finds a failing sequence. This
* functionality we get out-of-the-box without any additional code.
*/
com => com is _Digit n ?
Arbitrary.Shrink(n.Value).Select(Digit) :
EnumerableExt.Enumerate(com)
));
}