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There's an example in Programming Lua, 2nd Edition that looks like (with a few subtle modifications):
local x = 10000
local sqr = x / 2
sqr = (sqr + x / sqr) / 2
local err = math.abs(sqr^2 - x)
x = x - 1
until err < x / 10000
The output should be:
However, parrot-lua spits out a runtime error:
lua.pbc: example.lua:9: attempt to compare nil with number
example.lua:9: in main chunk
[PIR]: in function 'docall'
[PIR]: in function 'handle_script'
[PIR]: in function 'main'
In Lua, the scope of local variables declared inside a loop includes the condition as well. However, it seems that parrot-lua does not know about this common mistake.
Note that this behavior is new in Lua 5.1.