Re: finding keys in a table

["Alex Davies" <alex.mania@...>]

Hmmm. I actually meant:

tab[char] = (tab[char] or 0) + 1

Although it shouldn't make any difference.

I'm a bit confused though, because I measured:
 for i = 1, 1024*1024*64 do
   test.a = (test.a or 0) + 1
 end
versus:
 for i = 1, 1024*1024*64 do
   local count = test.a
   if count then
     test.a = count + 1
   else
     test.a = 1
   end
 end

And on my compiler/computer at least, the top one is consistently faster. No 
idea why, given that both give the same opcodes for the main loop:
 Gettable, Test, Add, Settable

Of course, if you mean that the first time through the loop would be faster 
in the bottom case you would be spot on. Still, if the loop takes any amount 
of time, I'd figure the first hit for each letter insignificant. Just an 
imo. In any case the top way is a lot neater. =)

Javier: Mike's way is fastest and neatest =)

- Alex

----- Original Message ----- 
From: "Hans Hagen" <pragma@wxs.nl>
> actually,
>
>     tab[char] = (count or 0) + 1
>
> is slower than
>
>     if count then
>         tab[char] = count + 1
>     else
>         tab[char] = 1
>     end
>
> (the if then variant takes 60% of the time of the or case; the interpreter 
> needs an extra LOADK)
>
> in a similar fashion, parallel assignments can be faster
>
> Hans