What is wrong with NULL • Hacker News Board

Re: What is wrong with NULL

#41

Post by vbezhenar » Mon, Aug 31, 2015, 9:19 PM UTC

protonfish wrote: post #29

bronson wrote: post #10

Uglier than a Windows backslash, odder than ===, more common than PHP, more unfortunate than CORS, more disappointing than Java generics, more inconsistent than XMLHttpRequest, more confusing than a C preprocessor, flakier than MongoDB, and more regrettable than UTF-16, the worst mistake in computer science was introduced in 1965. That could be the greatest intro sentence ever seen on Hacker News.

Pretty good, but I've never had a problem with an XMLHttpRequest being inconsistent. Everything else seems spot-on though.

XML is uppercase but Http is not. That seems to be inconsistent, though in some coding standards that's a correct naming scheme: acronyms with length less that 4 are named in uppercase (XML, URL) and acronyms with length >= 4 are named as Http. Another example is HttpURLConnection class from the standard Java library.

Re: What is wrong with NULL

#42

Post by paulddraper » Mon, Aug 31, 2015, 9:19 PM UTC

SamReidHughes wrote: post #11

NULL is okay as long as you pretend it doesn't exist. I mean, in these languages, uninitialized variables exist at some point (fields start uninitialized in constructor bodies, etc), and that's why there's null, instead of defining them with some garbage value that has undefined behavior. But the right solution for users is to just pretend that it can't exist, and that uninitialized variables have a garbage value. Of…

(1) It's true that a sentinel value like NULL can cut cycles. That's low-level code though, and not high-level code. I'd suggest that most code is (should be high level).

(2) It is true that you may have uninitialized values. There are several ways to address it. Java will not allow you to use uninitialized local variables. C/C++ leaves the values of some uninitialized variables undefined. There are several possible approaches. Treating null as a normal thing is not a good approach, though.

Re: What is wrong with NULL

#43

Post by benihana » Mon, Aug 31, 2015, 9:19 PM UTC

bronson wrote: post #10

Uglier than a Windows backslash, odder than ===, more common than PHP, more unfortunate than CORS, more disappointing than Java generics, more inconsistent than XMLHttpRequest, more confusing than a C preprocessor, flakier than MongoDB, and more regrettable than UTF-16, the worst mistake in computer science was introduced in 1965. That could be the greatest intro sentence ever seen on Hacker News.

Disagree. I really dislike that sentence stylistically. By the time the author got to the point, there was no way it could live up to that many words (that I mostly scanned, since they don't really add anything to the main point of the article).

The article is great, don't get me wrong, and I wouldn't have mentioned anything if you hadn't brought up this point, but I thought I would just provide a counter-point.

Re: What is wrong with NULL

#44

Post by choult » Mon, Aug 31, 2015, 9:19 PM UTC

protonfish wrote: post #29

bronson wrote: post #10

Uglier than a Windows backslash, odder than ===, more common than PHP, more unfortunate than CORS, more disappointing than Java generics, more inconsistent than XMLHttpRequest, more confusing than a C preprocessor, flakier than MongoDB, and more regrettable than UTF-16, the worst mistake in computer science was introduced in 1965. That could be the greatest intro sentence ever seen on Hacker News.

Pretty good, but I've never had a problem with an XMLHttpRequest being inconsistent. Everything else seems spot-on though.

Clearly you've only started using it in the past few years... It was horrific and totally inconsistent across browsers and between versions about 8 years ago and earlier.

Re: What is wrong with NULL

#45

Post by seertaak » Mon, Aug 31, 2015, 9:19 PM UTC

ant6n wrote: post #4

For statically typed languages this is definitely an issue, but for dynamic languages less so. In Python, I wouldn't use an optional value, x is None seems to be just fine. I'm still waiting for std::optional for C++.

Assuming x is not a boolean, I think

    not x

would be sufficient in the case of Python.

Re: What is wrong with NULL

#46

Post by sampo » Mon, Aug 31, 2015, 9:20 PM UTC

> If x is known to be a String, the type check succeeds; if x is known to be a Socket, the type check fails.

So the author is trying to explain what the null pointer exception is, but uses the concept of sockets in his example. I wonder, how many people know what a socket is but don't know what null pointer exception is?

Re: What is wrong with NULL

#47

Post by njharman » Mon, Aug 31, 2015, 9:20 PM UTC

> if (str == null || str == "")

Why not have null (and emptystring) eval to false? And

    if not str:
       str = 'wordup'

Re: What is wrong with NULL

#48

Post by mcguire » Mon, Aug 31, 2015, 9:21 PM UTC

Animats wrote: post #35

C++ introduced non-null references. But they didn't enforce them. There are still "I'm so l33t I can use null references" people. The new move semantics use null references for things moved from. C++ is trying to do Rust-like borrow checking without a borrow checker. Errors result in de-referencing null and crashing. Rust doesn't have null, but it has Option , which is often syntactic sugar for null. It's not that nu…

"Rust doesn't have null, but it has Option, which is often syntactic sugar for null."

In a sense, yes. But you have to do something positive before you can pretend that nothing is something. And the call to unwrap can be annotated with an argument as for why it can never fail, or why it's unimportant if it panics, or even be outlawed by a style guide.

"It's not that null is bad in itself. It's that having variables which might be null need to be distinguished from ones which can't be null."

Amen, brother.

Re: What is wrong with NULL

#49

Post by bcoates » Mon, Aug 31, 2015, 9:22 PM UTC

PaulAJ wrote: post #3

This mistake is fixed in Haskell.

Not completely. non-nullable by default is nice, ignoring possible nulls is nice, but Haskell's Maybe still suffers from premature generality by conflating all forms of absence. A 'Maybe T' is fundamentally, context-sensitively, not equivalent to any other 'Maybe T' in the same way all 'T's are. This is bad.

edit: carsongross beat me to what I'm talking about with a better explanation: https://news.ycombinator.com/item?id=10149129

Re: What is wrong with NULL

#50

Post by mcguire » Mon, Aug 31, 2015, 9:23 PM UTC

geofft wrote: post #34

It's worth noting that having a NULL, somewhere, is not so much a problem as forcing types to have a NULL. In this respect, e.g. Python and Rust both get it right: while Python has a None, and Rust has std::ptr::null(), an object that is a string cannot be any of those, because those are different types (NoneType and raw pointer, respectively). C's problem is that a string could be null, and there's no syntax for a n…

"In Python, you can also pass 42, [], or the sqlalchemy module. None isn't special here..."

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