Lua Trivia Answers

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Answer A

It depends what a.b is!

a = {}; b = {}; c = {}
print(a,b,c) --> a,b,c

a.b = function(...) print(...) end
a:b(c) --> a,c

mt = {}
mt.__call = function(...) print(...) end
a.b = setmetatable(b, mt)
a:b(c)   --> b,a,c
a.b(a,c) --> b,a,c (identical)

Furthermore, a, c, and the global environment table could invoke metamethods that call functions too.

Answer B

It prints
2       3       2
and not
1       4       6
as you would expected if you are a C programmer! This is simply because the -- sign in the third line is not interpreted as a variable decrement, but as the start of a comment... The ++ operator does not exist in Lua neither, but does not generate an error here because it is inside that comment!

Note that the lack of syntax highlight in the question was in fact intentional.

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Last edited October 25, 2008 8:22 pm GMT (diff)