Re: Exposure of nil to end-users

[Eva Schmidt <es@...>]

Hi Ben,

in any case you have to check if (value == nil).

Hm, what you would actually need is something like overloading the .. operator. 
I don't know if that is possible.

But maybe you could define your own concatentaion function, that lives within 
your environments metatable and call the .. only if the string value is ~= nil, 
otherwise concatenates to an empty string ""?

So you could hide the checking but avoid problem by concatenating a string to 
nil. After all, using .. by the user should be prohibited then somehow ...

Ok - just thoughts ... Maybe somebody as another idea :-)

Bye
Eva

Ben Harper wrote:
> I am using Lua as a language that allows end-users to manipulate
> database records.
> My problem is that I'm not sure how to expose NULL values to the user.
>
> In this example, value = nil
> User Types:      value .. "abc"
> User Expects:   'abc'
> User Gets:        Error: attempt to concatenate a nil value
>
> Has anybody had a similar problem, and how have you dealt with it?
>
> Thanks,
> Ben