Re: keys in tables

[PA <petite.abeille@...>]

On Dec 10, 2005, at 18:00, Gavin Wraith wrote:

> Somebody must have asked this before! Is there anybody
> who can claim to have written a Lua program that uses
> a table whose keys are neither numbers nor strings,
> and for which this feature is essential?

Hmmmm... not sure if it's truly "essential" as one could always devise  
a string representation of any tables. Nonetheless, here is an  example  
of a "notification center" (e.g. a dispatch table) along the lines of  
Cocoa's NSNotificationCenter:

http://dev.alt.textdrive.com/file/lu/LUNotification.lua

http://developer.apple.com/documentation/Cocoa/Reference/Foundation/ 
ObjC_classic/Classes/NSNotificationCenter.html

> When I first learned that Lua allowed any non-nil value
> as a key, I thought "Wow - democracy for table-keys".
> That was quite a time ago. But what properties do we actually
> require of keys in a table? 1) that keys are distinguishable,
> and sometimes 2) that keys form a linear order. Can anybody
> suggest any other qualities that might be desirable?

Immutability?

Cheers

--
PA, Onnay Equitursay
http://alt.textdrive.com/