ycitm

2 months agodiscuss

The next sentence in the quote hasn't aged so well - "What weather they shall have is not ours to rule."

Most importantly, this means my type system N-queens solution now works for an 8x8 chessboard (actually up to 10x10) instead of complaining about recursion depth:

https://www.richard-towers.com/2023/03/11/typescripting-the-...

ycitm

last yeardiscuss

Doesn't seem to be any discernable improvement on the Zoom Cat Lawyer.

ycitm

3 years agodiscuss

You can also play around with the code in the TypeScript playground:

https://www.typescriptlang.org/play?#code/PTAEEkDsAsEMBsCmAa...

ycitm

3 years agodiscuss

Ah, thank you so much! Great spot.

I've corrected this, and credited you in the errata - https://www.richard-towers.com/2023/03/11/typescripting-the-...

ycitm

3 years agodiscuss

I don't think there's any way to do iteration in the type system (other than recursion), so there's no way around it.

I considered forking the compiler to set a deeper limit, but at some point Typescript itself is going to stack overflow. Also that probably goes a bit beyond what Criss is expecting in an interview...

ycitm

3 years agodiscuss

I wondered if anyone would spot this :)

There's a recursion depth limit of 500 on the TypeScript compiler, which prevents this solution working for N > 7

Even Aphyr's original Haskell solution only demonstrates N = 6, so in some sense this is an improvement on the state of the art for type-level N Queens solutions /s

ycitm

3 years agodiscuss

The series is actually by Aphyr: https://aphyr.com/tags/interviews

This post is a pastiche of https://aphyr.com/posts/342-typing-the-technical-interview

ycitm

3 years agodiscuss

The runes are mostly "just because", but there is a reason.

Ideally, I would have written:

  type Nil = unique symbol

Which would ensure the Nil type wouldn't match with anything but itself. Unfortunately, the compiler doesn't allow unique symbol other than on const variables initialised with Symbol(). So I needed some meaningless symbols.

I could also have done

  type Nil = "nil"

But then it would have looked like the string meant something.

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