
In lua book (BTW, a question to Roberto: how high
is the finishing of THE BOOK in your priority list? ;) there is an
interesting example of using upvalues in Lua4:
sin = function (x)
return %sin(x*180/PI)
end
This thing is not directly reproducible in Lua5,
right? The way to do this in 5.0 I can think of is this:
local old_sin = sin
sin = function (x)
return old_sin(x*math.pi/180)  updated to
Lua5 specifics: convert back to accepting degrees ;)
end
Is this right? Is this the only way? Will it work
just the same? (I tested it to some expent, it produced similar result on my
test script for Lua4 and Lua5 versions).
P.S. I wonder if this discussion of upvalues os of
use to anybody (even me): those who use closure know what it is, those who don't
know  well, then just do not use them 8)
