Re: Killa: a scripting language based in Lua 5.2 with a JavaScript like syntax

[Dirk Laurie <dirk.laurie@...>]

Miles replying to Laurens:

>> I can't hope to convince you to use index base zero if you already
>> like index base 1, you are in your right.
>
> Actually I like base-0 better -- but not more than I like being able
> to use existing code.... :]
>

Lua is only very mildly base-1.  It affects table constructors,
the `table` library, and (I'm told) efficiency.

But nothing stops you from using index 0, or even index -1, -2, etc.
This is crucial.

I recently had to translate a program from Lua to a real base-1
language. The central bit of Lua code is

     p = {[-1]=0, [0]=1};
     for k=0,n-1 do
        p[k+1] = (x-a[k])*p[k] - b[k]*p[k-1]
     end

which is exactly the way the math is written in the textbook, except
on the page it appears with subscripts.  Writing the Lua code was
a no-brainer.

You can imagine what a PITA it is to do that in a language that does
not allow you to write or refer to p[-1] and p[0].  Are we going to
increase all indices by 2, and remember to do that on all the formulas
lower down also?  Sorry mate, the bugs won't just crawl in, they will
call their friends and their friends' friends too.  Are we going to
have extra variables pm1 and p0?  At least the bugs will show up as
references to non-existent indices so you have a chance of catching
them.  Are we going to write a nice object-oriented class?  That's
the canonic solution.  Hours and hours of "productive" programming;
I hope you get paid for doing it.

The problem is much the same in an base-0 language, although the
p0 solution is now less inconvenient than in base-1.  But it does
not go away: the textbook author uses negative indices in many other
places too, and the value is not always 0.

You don't properly appreciate how wonderfully versatile a Lua table
is until you need to go back for a while to a language that hasn't
got it.  The Lua solution, to allow any index, is so clean and
convenient.  It doesn't matter much what the index base is.

Miles again:
> In practice, I find I rarely notice the difference when writing Lua code.
>

Amen to that.