Capitolo 1 - Count invocations purely functional

[arialdomartini]

Riusciamo a fare questo usando solo funzioni e strutture immutabili?

Func<int, int> double = n => n * 2;

double(10).Should().Be(20);
double(10).Should().Be(20);
double(10).Should().Be(20);

??? doubleCount = double.andAlsoCountCalls();

doubleCount(10, count => count.Should().Be(1));
doubleCount(10, count => count.Should().Be(1));
doubleCount(10, count => count.Should().Be(1));

doubleCount
    (10, _ => {})
    (10, _ => {})
    (10, count => count.Should().Be(3));