> No nulls, no nullability bombs. I hate this meme. Null indicates something. If you disallow n...

fc417fc802 • yesterday at 2:42 AM • 1 reply • view on HN

> No nulls, no nullability bombs.

I hate this meme. Null indicates something. If you disallow null that same state gets encoded in some other way. And if you don't properly check for that state you get the exact same class of bug. The desirable type system feature here is the ability to statically verify that such a check has occurred every time a variable is accessed.

Another example is bounds checking. Languages that stash the array length somewhere and verify against it on access eliminate yet another class of bug without introducing any programmer overhead (although there generally is some runtime overhead).

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yencabulator • yesterday at 6:30 PM

The whole point of "no nullability bombs" is to make it obvious in the type system when the value might be not present, and force that to be handled.

Javascript:

  let x = foo();
  if (x.bar) { ... } // might blow up

Typescript:

  let x = foo(); // type of x is Foo | undefined
  if (x === undefined) { ...; return; } // I am forced to handle this
  if (x.bar) { ... } // this is now safe, as Typescript knows x can only be a Foo now

(Of course, languages like Rust do that cleaner, since they don't have to be backwards-compatible with old Javascript. But I'm using Typescript in hopes of a larger audience.)

alt Hacker News

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