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> It simply does not communicate anything to me to hear someone say "logically-speaking, there is no such thing as null" I've seen tons of complex and unwieldy

> It simply does not communicate anything to me to hear someone say "logically-speaking, there is no such thing as null" I've seen tons of complex and unwieldy code in my day. Often the complexity comes from illogic and incorrect modeling of how things are. So when someone points out a logical unnecessity, for a programmer to dismiss it as meaningless is to miss out. (In some logics,) there is no such thing as null and therefore you don't need it's representation to write effective programs. That's actually a valuable thing to say. Because from there you can start asking questions like why does it exist here or there? And then you can proceed to write more reasonable, less complex programs. I've had to fight ill-devised null semantics too many times to count in my programming life. To get concrete, there are things we know and things we don't. Most often null is used as a placeholder to say "I don't know." This leads to complexity because I'll then have to write code to branch on this one other value case (or at minimum defend, like the article points out). But if it's not logical per se, then what else can we do. What other way can I program that more reflects logic and our reasoning processes? That's a path to writing better, more maintainable programs. One revelation I got when having to model data in NoSQL after years of SQL is that while SQL makes you decide and write down NULL values for entity properties, NoSQL did not. If you don't know it, you don't write it down. It's that simple. And that is much more in line with the way that I contend with the things I don't know in my life. I don't go around re-iterating my lack of knowledge by referring to some logically non-existent value. I generally simple don't say things I don't know. Following this reasoning to a degree, and then I am writing programs that are much more ergonomic to the way people actually think.

3pt14159 8y ago
And yet when I data science with my dirty SQL, knowing that I've summed a collection that has a null value is super helpful because it shows that the query that I've made is fundamentally unknowable. Of course there are alternative ways of doing it: https://i.imgur.com/ENtJs.png https://i.imgur.com/ENtJs.png
jpz 8y ago
When one writes code which is close to the processor, for instance, one has a reason to write in C, one can represent an unallocated memory structure with a null pointer, or one can use a boolean value. A null value means something in that context. I don't see how it means nothing. If I have a tail-recursive function, I probably do not need null. But if I have a loop which may run 0 or more times, and need to catch the absence of runs, I need to model a None result. In that instance, the null has semantic meaning. I can use an algebraic type of course, but for the task I am doing, that may not be practical. Saying that null logically doesn't exist is not true if my context is the Linux kernel. The unqualified statement of such seems to be overly categorical, to me. I do like your analogy with NoSQL, I think it's an excellent point. Nullability in a JSON document for instance is better modelled with absence - however, with a language which is compile-time type-checked, those absent values may need to be present in materialised classes as nullable values (options if you like) - unless you're dictionaries all the way down like Python.

3pt14159 8y ago

And yet when I data science with my dirty SQL, knowing that I've summed a collection that has a null value is super helpful because it shows that the query that I've made is fundamentally unknowable. Of course there are alternative ways of doing it: https://i.imgur.com/ENtJs.png https://i.imgur.com/ENtJs.png

jpz 8y ago

When one writes code which is close to the processor, for instance, one has a reason to write in C, one can represent an unallocated memory structure with a null pointer, or one can use a boolean value. A null value means something in that context. I don't see how it means nothing. If I have a tail-recursive function, I probably do not need null. But if I have a loop which may run 0 or more times, and need to catch the absence of runs, I need to model a None result. In that instance, the null has semantic meaning. I can use an algebraic type of course, but for the task I am doing, that may not be practical. Saying that null logically doesn't exist is not true if my context is the Linux kernel. The unqualified statement of such seems to be overly categorical, to me. I do like your analogy with NoSQL, I think it's an excellent point. Nullability in a JSON document for instance is better modelled with absence - however, with a language which is compile-time type-checked, those absent values may need to be present in materialised classes as nullable values (options if you like) - unless you're dictionaries all the way down like Python.