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How would functional programming help you in this department?

• piaste 10y ago
  In C#, null is just one possible value of the regular type Foo. The compiler cannot tell whether you have started returning null where you previously only returned non-null values, nor can it tell whether you've handled those null values correctly at the consumption site. In F#, None is a subtype of the Option<Foo> union type, which is different from the plain Foo type and from the other subtype Some Foo. If you change a function that used to return a plain Foo into one returning Option<Foo>, every place in your code where that function is consumed will throw a compile error until you edit it to unwrap and handle the distinct Some Foo and None subtypes.
• actsasbuffoon 10y ago
  Many functional programming languages have stronger type systems than C#. They typically don't accept null as a valid substitute for any type. To represent a nullable type, you wrap the value in a generic container. Think of it as being like an array that contains at most 1 item. The interface of this generic container only allows you to interact with the (potentially) wrapped value in a way that is type safe. That doesn't completely eliminate having to think about how the business logic should differ for missing values, but it ensures that you'll never get a null pointer exception.