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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 :-)


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?