Re: upvalues actually are values?

[spir <denis.spir@...>]

On 23/10/2012 20:19, Johann Hibschman wrote:
> I'm curious: what languages would print 1 and 2 below? I can't think of one.
>
> The equivalent Scheme,
>
>     (define (inc i) (lambda (n) (+ n i))
>     (define i 1)
>     (define inc1 (inc i))
>     (inc1 0)
>     (set! i 2)
>     (inc1 0)
>
> should never ever print anything other than 1 and 1.

I was messing up 2 issues. The (simpler) example that shows the behaviour I had 
in mind is:

i = 1
inc1 = function (n) return n + i end

print (inc1(0))

i = 2
print (inc1(0))

And yes, now Lua also print 1 and 2.
Seems crazy to use this "feature", but I actually was caught once when writing a 
"method" outside the table defining the "type", which depended on a global 
acting as a kind of setting. Tgat's how I discovered the point. Now, why people 
find it more useful than dangerous (that closures close on vars, not data), I 
don't know. Also, it seems more complicated to implement, doesn't it?

Denis