Re: [Haskell-cafe] Error in array index.

2009/06/24 Daniel Fischer :

Am Mittwoch 24 Juni 2009 18:50:49 schrieb Jason Dusek:

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2009/06/24 Ketil Malde :

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So in effect, you have a zero-length underlying array, but the array implementation still keeps track of the real indices and tries to print some contents.  (Correct?)

I don't quite understand your reasoning here.

The 'length' of the array, as in 'number of elements' is calculated by multiplying the lengths in each dimension

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I don't know if that's how it's implemented, but that's the reasoning leading to an array of size 0.

That seems reasonable, actually. My system is nominally 64bit (it's MacIntel) but the kernel claims `i386` so there we are. It's too bad that indexes are `Int` instead of `Word` under the hood. Why is `Int` used in so many places where it is semantically wrong? Not just here but also in list indexing... Indices/offsets can only be positive and I can't see any good reason to waste half the address space -- yet we encounter this problem over and over again. This problem probably runs pretty deep. Just having a flexible "backing index type" is only part of the issue, since pointer indexing operations work with `Int` as well. If you wanted to hide all this stuff, you'd need to segment particularly large unboxed arrays... -- Jason Dusek