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Rici Lake wrote:
The real index name is the last localvar; it is not in scope until the loop
starts. Consequently, for loops correctly (imho) create a new index object
on each loop, which in turn means that upvalues work correctly.
In other words:
timestable = {}
for i = 1, 10 do
timestable[i] = function(j) return i * j end
end
will do the right thing in lua 5.1, and something quite different
in earlier versions.
Depends on how you interpret the for loop. If you interpret the loop as:
do
local i = 1
repeat
timestable[i] = function(j) return i * j end
i = i + 1
until i > 10
end
Then the right thing is the behavior of Lua 5.0.2 (in fact, this is the
way for is explained in the reference manual :-) ). You can easily have
it the other way by explicitely declaring another local:
timestable = {}
for i = 1, 10 do
local k = i
timestable[i] = function(j) return k * j end
end
The new way just makes it more convenient. Well, I'm sure this new way
will be documented in the 5.1 reference manual. :-) And the loop
variable is not really created anew each iteration; the same register is
reused. There is no performance penalty.
-- Fabio Mascarenhas