Re: Defensive Programming with Arrays (was Re: Speed of #t)
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- Subject: Re: Defensive Programming with Arrays (was Re: Speed of #t)
- From: steve donovan <steve.j.donovan@...>
- Date: 2010年12月13日 19:41:00 +0200
On Mon, Dec 13, 2010 at 7:36 PM, Javier Guerra Giraldez
<javier@guerrag.com> wrote:
> is there any undesired effect to table.insert(t,nil) when t is a
> well-formed array? after all, it's inserting nil at the end, leaving
> the table unchanged and therefore still holeless :-)
Sometimes we even rely on table.insert(t,nil) being a no-op.
The problem is that a map is supposed to take an array of N elements
and transform it into another array of N elements (unless you allow
it to 'filter' as well, which seems sneaky.)
t1 = map(fun,t2)
But this doesn't necessarily imply #t1 == #t2 if the for-loop was
numeric (most efficient method of mapping). Ah, the fun of holes!
steve d.