> So, for example, a place where null comes up. When you create a file. Programs that didn't check just threw up on an exception now. It is just as likely that

> So, for example, a place where null comes up. When you create a file. Programs that didn't check just threw up on an exception now. It is just as likely that without that option, the code would have just checked for a value, or thrown an error. So... what changed? What changed is that you are unable to propagate a null-that-shouldn't-be-null value to the rest of the program. If you have a value V that might be null, and you are supposed to return that value itself (not wrapped in an Option or anything like that, ie a 'nullable type'), all you can really do is: actually return a value of type V, or throw an exception. That's it! (To throw an exception is also something that can be done at any time in most statically typed languages, for any reason whatsoever. Throwing exceptions is usually not a question of the type correctness of a program (maybe it is in the case of checked exceptions?).) You can not give null as an output: you are supposed to give V as the output, not a nullable V. So you know exactly where in your program you are doing something 'unsafely', i.e. where you are not rigorously handling every case of the value of some type. Though 'unsafe' is a bit misleading, since you may very well intend to just throw an exception in the (perhaps deliberately possible) case that a value is null.