I can't give you any examples in F# from the top of my head, haven't touched it for a few months but I did ship software with it. I can give an example in Swift

I can't give you any examples in F# from the top of my head, haven't touched it for a few months but I did ship software with it. I can give an example in Swift: C#: ResultObject MyFunction(SomeObject some, AnotherObject another) You have no idea if every value you pass in is required, or if you would always get a ResultObject or also need to expect null. Could possibly throw an Exception as well. Swift: func myFunction(some: SomeObject, another: AnotherObject?) throws -> ResultObject Forces you to give SomeObject, but you can pass nil to AnotherObject if you would like to, and the code inside this function will be forced to deal with it. Also it will always return ResultObject unless it throws an Error. You will have no surprises using Swift while C# forces you to guess unless you know the inside of the function. F# works the same as Swift in that regard. You need to be explicit about nullability and mutability, and if it is nullable you are forced to deal with it it before you use it. Immutable and non-nullable is just easier to use. The leap between C# and F# is much bigger because C# is really good and F# is a real functional language where Objective-C was older and Swift is less functional. Same goes for Java vs. Kotlin. Android Java is terrible compared to C# while Kotlin is much more similar in syntax.