Re: ## operator (error)

Thank you for your comments.

Regarding automatic coercion between strings and numbers being a bad (‘not good’) thing, I’d certainly be in the minority group then, among those who strongly disagree with this, and for me this is just one of the many reasons to like Lua.

My reasoning is this:

From a human point of view numbers are (have always been) nothing more than strings of digits, just like words are strings of letters. Think how you write them on paper, or when you type.

Only for computing convenience (based on today’s technologies) we have made a ‘special arrangement’ for numbers to be treated differently internally. But, in an ideal world, a computing language should hide whatever machine requirements from the user as much as possible/feasible. There is nothing wrong with thinking of numbers as strings that just *happen* to contain mostly digits. So, in my view deprecating this ‘bad thing’ would be an utter mistake. Lua is already in the right direction to the ideal, why go back?

From: Tim Hill

It’s pretty much agreed that the automatic coercion between strings and numbers in Lua is not good, and is usually discouraged (and there have been discussions about deprecating it). And one of the reasons it’s not good is the very example you give. The “..” operator is non-polymorphic; it always operates on strings[1], so there is no ambiguity as to the desired type of the operator arguments. The “#” operator is polymorphic, and so type coercion is far more ambiguous (and therefore should be avoided). And if you REALLY need # on numbers then it can be added via the C API by adding a metatable to the number type.

—Tim

[1] Ignoring metatables, that is.