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0 pointspatrec4y ago0 comments

> The argument for 1-based indexing with inclusive upper bounds is that binary heaps are easier to write this way.

Nope. The argument for 1-based indexing with inclusive upper bounds is that, to express ranges, exclusive indexes require you to have a bogus just-one-beyond-the-largest-valid-index element and a way to get the successor for every index. This is a giant PITA for anything but integers (MAX_INT, and x+1), which is why every single programming language I can think of also has end-inclusive ranges in some contexts. If you don't believe me try writing regexps with end-exclusive ranges.

On the other hand, there is no natural way to express empty ranges with 1-based indexing.

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anonymoushn4y ago· 2 in thread

I'd love to learn more about writing regexps with various kinds of ranges. I don't see the issue, but it's very likely that I'm missing something.

patrecOP4y ago

Here's what a regexp for a C-style identifier looks like (ranges are inclusive):

    [a-zA-Z_][a-zA-Z0-9_]*

Here's what the same regexp would look like if regexp ranges were end-exclusive:

    [a-{A-[][a-{A-[0-:_]*

Do you see the issue now? Of course if regexps really worked that way, you'd be better off doing this instead:

    [a-zzA-ZZ][a-zzA-ZZ0-99_]

But that specific trick only works because regexp ranges occur in a set union context.

anonymoushn4y ago

I see, the `a-z` range has an inclusive upper bound. That makes sense and it really should be like that.

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