Re: Lua is about to become history

[Reuben Thomas <rrt@...>]

On Wed, 3 May 2006, John D. Ramsdell wrote:

> I think you have to be very careful about making this case.  How
> tolerant of backwards-incompatibility do you thing the Lua user base
> would be if the Lua authors modernized the language to support
> zero-based array and string indexing?  The greater difficulty of
> writing correct code using one-based array indexing was obvious to all
> when Fortran and C were two of the few major languages available, and
> the lesson was not lost by the designers of the current popular
> languages, such as Python.  But at this stage, do you really think
> that wart can be fixed?

Icon and Lua both demonstrate the benefit of 1-based indexing over 
0-based: the ability to count forward from the start of a string and 
backwards from the end symmetrically: 1 points to (just before) the 
first character and -1 to (just before) the last. Hence, 0 points to 
the end of the string, which seems a little odd, but if you use 
zero-based addressing, you can no longer point to the end of the string.

There's another argument about whether you point at characters or the 
gaps between them: if you insist on pointing at characters, you lose the 
property

  string.len(string.sub(s, a, b)) == b - a

for a, b of the same sign (and you STILL can't point at the end of a 
string!).

It's not at all clear to me that 1-based indexing is inherently worse. 
It gets you into trouble when you mix arrays and pointers, but who does 
that nowadays? APL, a language whose numerical properties are most 
carefully thought out, defaults to 1-based.

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