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Re: why the array index has to start at 0??

by rovf (Priest)
on Jun 23, 2009 at 11:11 UTC ( #773966=note: print w/ replies, xml ) Need Help??


in reply to why the array index has to start at 0??

the $[ variable helps us to set the first element in an array

Changing $[ is nearly always evil. The only other language I know which has such a bizarre mechanism is APL.

I remember back then when programming in languages such as PL/1, Algol etc., that I found it very cool to be able to declare arbitrary index ranges for arrays, so I could for example say that array indexing started at 4711, if I wanted to. I was able to choose for each array individually the way indexing worked. In practice, it turned out that nearly all arrays started at 0. A few (in particular in mathematical problems involving matrices and vectors), my arrays started at 1, simply because for some obscure reasons, mathematicians seem to prefer starting at 1 instead of 0 (or -100). Occasionally, I found it handy to have an array starting at -1. The pleasure of this flexibility comes however at the price of additional headache for the poor fellows who had to understand my code, because they now had to take into account with each array the lower bound as well.

So, if you feel so comfortable to count from one, just take a zero-based array and use element zero for storing your teabags. Fortunately, our computers nowadays have enough storage space that we don't have to worry about wasting an array element...

-- 
Ronald Fischer <ynnor@mm.st>


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Re^2: why the array index has to start at 0??
by dsheroh (Parson) on Jun 23, 2009 at 12:12 UTC
    The only other language I know which has such a bizarre mechanism is APL.

    I don't know about current versions, but, back in the Visual Basic 3 era, VB had the option base statement which could be used to change the starting index of arrays. As I recall, even VB programmers quickly figured out that using it was generally a bad idea.

      Now as you say it, I darkly remember that option base already existed at the time where VB did have the vancy "visual" sticker attached and was just called "BASIC". It is interesting that the same plunder had been incorparted at least three times in history - BASIC being first, followed by APL, then Perl.

      -- 
      Ronald Fischer <ynnor@mm.st>

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