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C# only kind of gives you this. When I said "the problem with languages that have null", that's really what I meant. There definitely could be a static language

C# only kind of gives you this. When I said "the problem with languages that have null", that's really what I meant. There definitely could be a static language that let you choose if something is nullable or not. But really, at that point it's just sugar for an option type.

dragonwriter 12y ago
C# is absolutely a static language that lets choose if something is nullable or not, there is no "kind of" about it. > But really, at that point it's just sugar for an option type. No, having a the free choice not use nullable types doesn't make the languages nullable types into sugar for option types. Nullable types don't compose the way option types do -- the issue in the article this thread is about isn't about whether or not you have the choice for nullable types, its about the fact they don't compose so you can distinguish a function returning a null as a substantive value because the thing you tried to store was also a nullable type and had a null value (Just None, in a world with Options instead of nullable types) or where the null is a result of the lookup failing (None, in a world with Options instead of nullable types.) The deficiency of nullable types in C# compared to Options isn't the lack of choice of writing non-nullable types -- as you certainly have that choice for any data you need to represent -- its that nullabe types don't compose the way Options do.
- wtetzner 12y ago
  As far as I understand, the only way to get a type that's not nullable is to make a struct. How do you specify that a function can take a non-nullable string?
  - dragonwriter 12y ago
    > As far as I understand, the only way to get a type that's not nullable is to make a struct. Well, any value type -- but, yes, a custom type has to be a struct to not be nullable. > How do you specify that a function can take a non-nullable string? "string" in C# is the name of a particular reference (and hence, nullable) type. If you want a function that takes a non-nullable sequence of characters, that's quite possible, but the type of its argument won't be string. (The fact that there is no such type predefined and the entire .NET framework library is built around the assumption that if you want a sequence of characters you are going to use the built-in, reference -- and therefore nullable -- string type is an issue with the cost, in programmer-time, of doing this for any substantial use, but its not a "the language doesn't let you have a non-nullable type for any kind of data you want" issue.)

dragonwriter 12y ago

C# is absolutely a static language that lets choose if something is nullable or not, there is no "kind of" about it. > But really, at that point it's just sugar for an option type. No, having a the free choice not use nullable types doesn't make the languages nullable types into sugar for option types. Nullable types don't compose the way option types do -- the issue in the article this thread is about isn't about whether or not you have the choice for nullable types, its about the fact they don't compose so you can distinguish a function returning a null as a substantive value because the thing you tried to store was also a nullable type and had a null value (Just None, in a world with Options instead of nullable types) or where the null is a result of the lookup failing (None, in a world with Options instead of nullable types.) The deficiency of nullable types in C# compared to Options isn't the lack of choice of writing non-nullable types -- as you certainly have that choice for any data you need to represent -- its that nullabe types don't compose the way Options do.

wtetzner 12y ago
As far as I understand, the only way to get a type that's not nullable is to make a struct. How do you specify that a function can take a non-nullable string?
- dragonwriter 12y ago
  > As far as I understand, the only way to get a type that's not nullable is to make a struct. Well, any value type -- but, yes, a custom type has to be a struct to not be nullable. > How do you specify that a function can take a non-nullable string? "string" in C# is the name of a particular reference (and hence, nullable) type. If you want a function that takes a non-nullable sequence of characters, that's quite possible, but the type of its argument won't be string. (The fact that there is no such type predefined and the entire .NET framework library is built around the assumption that if you want a sequence of characters you are going to use the built-in, reference -- and therefore nullable -- string type is an issue with the cost, in programmer-time, of doing this for any substantial use, but its not a "the language doesn't let you have a non-nullable type for any kind of data you want" issue.)