xxxxxxxxxx
if a ~= b then
-- Do something
end
if not boolean_expression then
-- Do something
end
if not (a == b) then
-- Do something
end
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-- if-then
if a < 0 then a = 0 end
-- if-then-else
if a < b then return a else return b end
-- if-then-elseif-then-else
if a < 0 then
x = 0
elseif a > 1 then
x = 1
else
x = a
end