Re: lists with nil play nice for Lua 5.2

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

On Aug 04, 2007, at 11:23, Duck wrote:

> So don't have holes in arrays :-)

Well... varargs routinely have nil values in them.... don't use varargs 
then?!? At that rate, not much will be left of Lua. Plus, there is no 
compelling reason for such a small, tight language to be littered with 
body-traps, isn't it?

In any case, here is a revisited 'tuple' implementation of sort:

Tuple = function( ... )
    local aList = { n = select( '#', ... ), ... }

    return function( aKey, anIndex )
        local anIndex = aKey or ( ( anIndex or 0 ) + 1 )
        local aValue = aList[ anIndex ]

        if aKey == '#' then
            return aList.n
        elseif aKey == '*' then
            return unpack( aList, 1, aList.n )
        elseif aKey then
            return aValue
        elseif anIndex <= aList.n then
            return anIndex, aValue
        end
    end
end

Usage example:

local aTuple = Tuple( nil, 'a', nil, 'b', nil, 'c', nil )

print( aTuple( '#' ) ) -- count
print( aTuple( '*' ) ) -- all values
print( aTuple( 2 ) ) -- one value

for anIndex, aValue in aTuple do -- enumerate
    print( anIndex, aValue )
end

> 7
> nil     a       nil     b       nil     c       nil
> a
> 1       nil
> 2       a
> 3       nil
> 4       b
> 5       nil
> 6       c
> 7       nil